Biochemistry

Many teenagers especially girls are very concerned about aging. As a result, this post is especially important for you. The purpose is to educate youngster some basic knowledge of maintaining their young and youthful appearance, longevity of life and staying with a healthy lifestyle. I will try to put this post as elucidating as possible so everybody who read can at least grab more than 50% of what I write; although some scientific terms seem to be hard to understand, I will try to explain each and every of the definition as much as possible. Let's start with some of the easy one.

Ionizing radiation - When we are talking about ionizing radiation in regards to staying young, we are talking about the ultraviolet radiation (UV ray) emitted from the sun which destroy our skin cells. Although X-ray is also an ionizing radiation, we are not talking about that since just one X-ray scan doesn't do you as much harm as the daily exposure to UV ray from the sun. Despite providing us with Vitamin D (a coenzyme important for the correct formation of our born and absorption of calcium), UV ray can also damage our cells DNA (causing cancer or sunburn), killing our cells (damaging factor), reducing the collagen in our face (more crevice formation that make us look older), causing free radical on our cells (free radical are high energy electron or ions that damage our cells such as destroying the DNA and this may cause benign or malignant tumors whereas malignant tumor is definitely a cancer). To stay young, it is advisable for you to put on sunscreen or lotion with zinc and antioxidant ingredient when you are exposing to the afternoon sunlight. Take note that UV ray can pass through some umbrella, the purpose of umbrellas are to shed visible light but not UV ray so do not assume that you are protected if you have an umbrella.

Antioxidant - As mention in the previous paragraph, what is antioxidant? Free radials are generated from your body during metabolism or when you are exposed to ionizing radiation. Free radials cause damages to the cell, sometime it can be so serious such that the cell becomes cancerous. The purpose of antioxidant is to neutralize the free radical so that there are lesser free radical in our body, thus lesser harms and therefore slower aging. To stay young, eat antioxidant such as lipoic acid, Vitamin C and E TOGETHER with many types of fruits and vegetables. You cannot totally depend on supplement as there are over 100 types of chemicals in fruits that work together to scavenge free radicals from your body.

Carbohydrate - Eating less carbohydrate can lead to longevity since glucose restriction means slower metabolism in our cells. When our cell metabolism slow down, lesser free radials are produced, thus, we will age slowly since there are lesser damages on our body. For some girls who are on high carbohydrate and fats restriction, because you are afraid that you may become fat even though you are underweight, you may have Anexoria nervosa. I have seen some of my teen friends who look normal weight as they restrict diet but have gastric problem after doing this for long term and they are still restricting carbohydrate. This is not the right way of doing since they will not get enough nutrient from food, thus slowing their growth rate during their puberty time. The right solution is to eat moderately, not too much such that it can gain you much fats or too little that can cause you gastric pain. Your existing health is your first priority but not spoiling one system for the purpose of losing weight. Strictly do not eat medical pills to slim down other than vitamins and minerals. Medical pills are harmful/cannot be trust, they can damage your livers and kidney for long term consumption. If half of your liver or kidneys are damaged, you wouldn't know since no symptoms will appear until 90% of it is damaged so you need to be careful.

Having enough sleep - Sleeping (not resting) is very important. While we are sleeping, our cell metabolism slow down, lesser free radials are produced. Therefore, people who sleep enough will look younger. When we are sleeping, our body undergoes a few cycle of random eyes movement, it is where our body becomes active, idle, active, idle, many repeating cycle for every few hours. This is the lay man term, in scientific terms, it is more than this but idle body does not happen when you are resting, except that when you are sleeping. Not only sleeping for a long time, a person must sleep at the right time; it means you sleep when you are sleepy but not sleeping too lately as it can affect your body clock. When your body is producing melatonin preparing for you to sleep, you force high production of Epinephrine while your body is producing melatonin at the same time. Does that make you feel actively drowsy; confused?

Forming in the fermenter is usually caused by the usage of protein such as corn steep liquor. Foaming can cause removal of cells by autolysis and further realease of microbial cell proteins will probably increase stability of form.

Problems with foaming -> Reduction in working volume fermenter due to oxygen exhuausted gas bubbles circulating in system. Low mass and heat transfer rate. Invalid process data due to interference at sensing electrodes and incorrect monitoring and control. Biological problems include deposition of cells in upper parts of the fermenter. Problems of sterlise operation with air exit filters of fermenters become wet.

An ideal anti-forming method must be used so as to increase the yield and to make sure that the cell consume the food in the tank but not the anti-forming agent. Ideal antiform should disperse readily and have fast action on existing form, should be active at low concentration, should be long acting in preventing new form formation, should not be metabolized by the microorganism, should not be toxic to microorganism, human, animals, birds and the environment, should not cause any problems in product extraction and purification, should not cause any handling hazards, should be cheap and readily available, should have no effect on oxygen transfer, should be heat sterilisable.

Examples of antiforming agents are alcohols, esters, fatty acids and derivatives, silicones, sulphonates and polypropylene glycol.

Before we start a large scale batch fermentation, we usually build our size from a small shaking flask before we transfer the cell into the large fermenter.

Here is the inoculum requirements -> It must be healthy, active and this tell a short lag phase in the fermentation process. It must be available in large and sufficient amount to provide inoculum of optimium size. It must be in a suitable morphological form. It must be free from contamination. It must retain its product formaing capabilities.

Clean In Place is often use in chemical plant to clean vessel and is usually use to clean the without the need to do manual cleaning.

Theodor Escherich first described E. coli in 1885, as Bacterium coli commune, which he isolated from the feces of newborns. It was later renamed Escherichia coli, and for many years the bacterium was simply considered to be a commensal organism of the large intestine. It was not until 1935 that a strain of E. coli was shown to be the cause of an outbreak of diarrhea among infants.

E. coli and its relatives are known to microbiologists as "enteric bacteria", because they live in the intestinal tract of humans and other animals. The best known other enteric bacteria are Salmonella, which includes the agent of typhoid fever, and Shigella, which is the bacterial cause of dysentery.

E. coli is in the bacterial family Enterobacteriaceae, which is made up of Gram-negative, nonsporeforming, rod-shaped bacteria that are often motile by means of flagella. The majority of strains grow well on the usual laboratory media in both the presence and absence of oxygen, and metabolism can be either by respiration or fermentation.

For most of the 20th century, E. coli has been used as the principal indicator of fecal pollution in both tropical and temperate countries. E. coli comprises about 1% of the total fecal bacterial flora of humans and most warm-blooded animals. Sewage is always likely to contain E. coli in relatively large numbers. In addition, E. coli, being a typical member enteric bacterium is presumed to have survival characteristics very similar to those of the well-known pathogens such as Salmonella and Shigella. Thus, E. coli has been used world-wide as an indicator of fecal microbiological contamination. As such an indicator organism, its value is significantly enhanced by the ease with which it can be detected. and cultured.

Tests to identify isolates as E. coli have, of necessity, been simple tests designed predominantly to differentiate them from organisms normally associated with uncontaminated water. Since full biochemical analyses are not generally performed, the term "coliform" has been coined to describe E. coli-like organisms that satisfy these limited tests. As a result, regulations are promulgated throughout the world defining standards for water based on the so-called "coliform count." For example, in the U.S., according to a regulation published in the Federal Register (1986), there is a requirement that there be 0 coliforms/100 ml drinking water, as determined by any method for any sampling frequency.

Since not all organisms which meet the criteria of a coliform are associated with the intestinal tract (some may be free-living), a further distinction must be made between "fecal coliforms" (E. coli) and "nonfecal coliforms" (e.g. Klebsiella and Enterobacter). The nonfecal coliforms are regularly found in soil and water and in associations with plants, so that their occurence does not necessarily indicate fecal pollution.

In order to distinguish E. coli from related species likely to be found naturally in the environment, a battery of tests called the IMViC reactions was developed in order to differentiate fecal coliforms from nonfecal coliforms. IMViC is an acronym in which the capital letters stand for Indole, Methyl red, Voges-Proskauer, and Citrate.) The IMViC set of tests examines: the ability of an organism to (1) produce Indole; (2) produce sufficient acid to change the color of Methyl red indicator; (3) produce acetoin, an intermediate in the butanediol fermentation pathway (a positive result of the Voges-Proskauer test); and (4) the ability to grow on Citrate as the sole source of carbon. E. coli is positive in the first two tests and negative in the second two; nonfecal coliforms are the opposite - negative in the first two tests and positive for the second two.

If E. coli is detected in water, it is an indication of fecal pollution. Most-likely the strain of E. coli is a harmless non pathogen, but the indication is that other pathogenic intesdtinal microbes could also be present. The pathogenic fecal coliforms (e.g. Salmonella and Shigella ) can be readily distinguished from strains of E. coli on the basis of a lactose fermentation test. All strains of E. coli ferment the sugar lactose while those of Salmonella and Shigella do not.

The International Commission on Microbiological Specifications for Foods (ICMSF, 1978) has adopted a set of standard techniques for the enumeration of E. coli in food products, accepted by the International Standards Organization (ISO, 1984). This method employs the use of lauryl sulfate tryptose broth at 35 or 37°C as a mildly selective-enrichment medium. This is followed by growth in EC broth containing 0.15% bile salts at 45°C as a second selective step. The ability to produce indole from tryptophan (in tryptone broth) at 45°C defines the strains as E. coli. These tests miss some types of E. coli, such as those most closely related to the Shigella group, but it is the detection of possible fecal contamination that is important in these tests rather than the presence of specific types.

There is no method for the detection of E. coli in water that is accepted throughout the world. In the US, a standard method using membrane filter enumeration for both total and thermotolerant coliforms has been established (American Public Health Association (1986). Further IMViC tests on selected isolates can then be performed as described above.

In the UK, the definition of E. coli in water microbiology is also based on the ability to produce gas from lactose and produce indole from tryptophan at 44°C. A method for enumeration employs a standard multiple tube test with a modified glutamate synthetic medium at 37°C as a first selective step, followed by further cultivation in standard media at 44°C.

le large numbers of E. coli will be found in fecal specimens or specimens contaminated with feces or intestinal contents, most other clinical specimens are usually not contaminated with E. coli. The major exception is urine, which requires special attention in the clinical situation. From those specimens in which E. coli is likely to be present in large numbers, direct plating on media such as MacConkey agar or Eosin Methylene Blue (EMB) agar is sufficient. If the number of E. coli is likely to be very low or the amount of specimen is limited, enrichment in a rich nutrient medium such as brain heart infusion broth may be used. A number of different commercially available kits are generally used to identify the isolates as E. coli.

From specimens likely to contain only a few viable E. coli cells, such as blood from patients suspected of having E. coli bacteremia, various enrichment procedures are used. Identification follows standard bacteriological techniques.

A fluorogenic detection method has been developed based on the cleavage of methylumbelliferyl-D-glucuronide (MUG) to the free methylumbelliferyl moiety, which fluoresces a blue color after irradiation with long-wave ultraviolet radiation. Although strains of E. coli are generally positive in this test, some strains of Salmonella, Shigella, and Yersinia are also capable of splitting MUG; the latter two genera are usually not present in food. A disadvantage is that enterohemorhagic E. coli (EHEC) strains are generally negative in this test. MUG can be added to various selective media, so there is a great potential in its use for detecting E. coli.

Automated or semi-automated systems are also being used for the detection of E. coli as part of the detection methods for Enterobacteriaceae. Techniques involving impedance measurements have shown promise. Other techniques such as immunoassays and nucleic acid hybridization studies can also be used to enumerate E. coli, and DNA probes directed at a number of genes have also been developed.

Physiologically, E. coli is versatile and well-adapted to its characteristic habitats. In the laboratory it can grow in media with glucose as the sole organic constituent. Wild-type E. coli has no growth factor requirements, and metabolically it can transform glucose into all of the molecular components that make up the cell. The bacterium can grow in the presence or absence of O2. Under anaerobic conditions it will grow by means of fermentation, producing characteristic "mixed acids and gas" as end products. However, it can also grow by means of anaerobic respiration, since it is able to utilize NO3 or fumarate as final electron acceptors for respiratory electron transport processes. In part, this adapts E. coli to its intestinal (anaerobic) and its extraintestinal (aerobic or anaerobic) habitats.

In the ecological niches that E. coli occupies and its abilities to grow both aerobically and anaerobically are important. E. coli is well adapted to its intestinal environment as it is able to survive on a relatively limited number of low-molecular weight substances, which may only be available transiently and at relatively low concentrations. The generation time for E. coli in the intestine is thought to be about 12 hours. The type of nutrients available there to E. coli consist of mucus, desquamated cells, intestinal enzyme secretions, and incompletely digested food. Given the absorption capacity and efficiency of the intestine, there are probably only small amounts free carbohydrates or other easily absorbable forms of nutrients, and there is competition from hundreds of other types pf bacteria. A similar situation probably also applies to sources of nitrogen.

In its natural environment, as well as the laboratory, E. coli can respond to environmental signals such as chemicals, pH, temperature, osmolarity, etc., in a number of very remarkable ways considering it is a single-celled organism. For example, it can sense the presence or absence of chemicals and gases in its environment and swim towards or away from them. Or it can stop swimming and grow fimbriae that will specifically attach it to a cell or surface receptor. In response to changes in temperature and osmolarity, it can vary the pore diameter of its outer membrane porins to accommodate larger molecules (nutrients) or to exclude inhibitory substances (e.g. bile salts). With its complex mechanisms for regulation of metabolism the bacterium can survey the chemical content its environment in advance of synthesizing any enzymes necessary to use these compounds. It does not wastefully produce enzymes for degradation of carbon sources unless they are available, and it does not produce enzymes for synthesis of metabolites if they are available as nutrients or growth factors in the environment.

The commensal E. coli strains that inhabit the large intestine of all humans and warm-blooded animals comprise about 1% of the total bacterial biomass. This E. coli flora is in constant flux. One study on the distribution of different E. coli strains colonizing the large intestine of women during a one year period (in a hospital setting) showed that 52.1% yielded one serogroup, 34.9% yielded two, 4.4% yielded three, and 0.6% yielded four. The most likely source of new serotypes of E. coli is acquisition by the oral route. To study oral acquisition, the carriage rate of E. coli carrying antibiotic-resistance (R) plasmids was examined among vegetarians, babies, and nonvegetarians. It was assumed that nonvegetarians might carry more E. coli with R factors due to their presumed high incidence in animals treated with growth-promoting antimicrobial agents. However, omnivores had no higher an incidence of R-factor-containing E. coli than vegetarians, and babies had more resistant E. coli in their feces than nonvegetarians. No suitable explanation could be offered for these findings. Besides, investigation of the microbial flora of the uninhabited Krakatoa archipelago has shown the presence of antibiotic-resistant E. coli associated with plants.

Uropathogenic E. coli cause 90% of the urinary tract infections (UTI) in anatomically-normal, unobstructed urinary tracts. The bacteria colonize from the feces or perineal region and ascend the urinary tract to the bladder. Bladder infections are 14-times more common in females than males by virtue of the shortened urethra. The typical patient with uncomplicated cystitis is a sexually-active female who was first colonized in the intestine with a uropathogenic E. coli strain. The organisms are propelled into the bladder from the periurethral region during sexual intercourse. With the aid of specific fimbriae they are able to colonize the bladder.

The frequency of the distribution of the host cell receptor for the bacterial fimbriae plays a role in susceptibility and explains why certain individuals have repeated UTI caused by E. coli. Uncomplicated E. coli UTI virtually never occurs in individuals lacking the receptors.

Neonatal meningitis affects 1/2,000-4,000 infants. Eighty percent of E. coli strains involved synthesize K-1 capsular antigens (K-1 is only present 20-40% of the time in intestinal isolates).

E. coli strains invade the blood stream of infants from the nasopharynx or GI tract and are carried to the meninges.

Epidemiologic studies have shown that pregnancy is associated with increased rates of colonization by K-1 strains and that these strains become involved in the subsequent cases of meningitis in the newborn. Probably, the infant GI tract is the portal of entry into the bloodstream. Fortunately, although colonization is fairly common, invasion and the catastrophic sequelae are rare.

Neonatal meningitis requires antibiotic therapy that usually includes ampicillin and a third-generation cephalosporin.

As a pathogen, E. coli, of course, is best known for its ability to cause intestinal diseases. Five classes (virotypes) of E. coli that cause diarrheal diseases are now recognized: enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), and enteroaggregative E. coli (EAggEC). Each class falls within a serological subgroup and manifests distinct features in pathogenesis.

Definition
Essential to human health, omega-3 fatty acids are a form of polyunsaturated fats that are not made by the body and must be obtained from a person's food.

Purpose
Eating foods rich in omega-3 fatty acids is part of a healthy diet and helps people maintain their health.

Description
In recent years, a great deal of attention has been placed on the value of eating a low fat diet. In some cases, people have taken this advice to the extreme by adopting a diet that is far too low in fat or, worse yet, a diet that has no fat at all. But the truth is that not all fat is bad. Although it is true that trans and saturated fats, which are found in high amounts in red meat, butter, whole milk, and some prepackaged foods, have been shown to raise a person's total cholesterol, polyunsaturated fats can actually play a part in keeping cholesterol low. Two especially good fats are the omega-3 fatty acids and the omega-6 fatty acids, which are polyunsaturated.

Two types of omega-3 fatty acids are eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA), which are found mainly in oily cold-water fish, such as tuna, salmon, trout, herring, sardines, bass, swordfish, and mackerel. With the exception of seaweed, most plants do not contain EPA or DHA. However, alpha-linolenic acid (ALA), which is another kind of omega-3 fatty acid, is found in dark green leafy vegetables, flaxseed oil, fish oil, and canola oil, as well as nuts and beans, such as walnuts and soybeans. Enzymes in a person's body can convert ALA to EPA and DHA, which are the two kinds of omega-3 fatty acids easily utilized by the body.

Many experts agree that it is important to maintain a healthy balance between omega-3 fatty acids and omega-6 fatty acids. As Dr. Penny Kris-Etherton and her colleagues reported in their article published in the American Journal of Nutrition an over consumption of omega-6 fatty acids has resulted in an unhealthy dietary shift in the Americandiet. The authors point out that what used to be a 1:1 ratio between omega-3 and omega-6 fatty acids is now estimated to be a 10:1 ratio. This poses a problem, researchers say, because consuming some of the beneficial effects gained from omega-3 fatty acidsare negated by an over consumption of omega-6 fatty acids. For example, omega-3 fatty acids have anti-inflammatory properties, whereas omega-6 fatty acids tend to promote inflammation. Cereals, whole grain bread, margarine, and vegetable oils, such as corn, peanut, and sunflower oil, are examples of omega-6 fatty acids. In addition, people consume a lot of omega-6 fatty acid simply by eating the meat of animals that were fed grain rich in omega-6. Some experts suggest that eating one to four times more omega-6 fatty acids than omega-3 fatty acids is a reasonable ratio. In other words, as dietitians often say, the key to a healthy diet is moderation and balance.

The Health Benefits of Omega-3 Fatty Acids
There is strong evidence that omega-3 fatty acids protect a person against atherosclerosis andtherefore against heart disease and stroke, as well as abnormal heart rhythms that cause sudden cardiac death, and possibly autoimmune disorders, such as lupus and rheumatoid arthritis. In fact, Drs. Dean Ornish and Mehmet Oz, renowned heart physicians, said in a 2002 article published in O Magazine that the benefits derived from consuming the proper daily dose of omega-3 fatty acids may help to reduce sudden cardiac death by as much as 50%. In fact, in an article published by American Family Physician, Dr. Maggie Covington, a clinical assistant professor at the University of Maryland, also emphasized the value of omega-3 fatty acids with regard tocardiovascular health and referred to one of the largest clinical trials to date, the GISSI-Prevenzione Trial, to illustrate her point. In the study, 11,324 patients with coronary heart disease were divided into four groups: one group received 300 mg of vitamin E, one group received 850 mg of omega-3 fatty acids, one group received the vitamin E and fatty acids, and one group served as the control group. After a little more than three years, "The group given omega-3 fatty acids only had a 45% reduction in sudden death and a 20% reduction in all-cause mortality," as stated by Dr. Covington.

According to the American Heart Association (AHA), the ways in which omega-3 fatty acids may reduce cardiovascular disease are still being studied. However, the AHA indicates that research as shown that omega-3 fatty acids:

* decrease the risk of arrthythmias, which can lead to sudden cardiac death
* decrease triglyceride levels
* decrease the growth rate of atherosclerotic plaque
* lower blood pressure slightly

In fact, numerous studies show that a diet rich in omega-3 fatty acids not only lowers bad cholesterol, known as LDL, but also lowers triglycerides, the fatty material that circulates in the blood. Interestingly, researchers have found that the cholesterol levels of Inuit Eskimos tend to be quite good, despite the fact that they have a high fat diet. The reason for this, research has found, is that their diet is high in fatty fish, which is loaded with omega-3 fatty acids. The same has often been said about the typical Mediterranean-style diet.

Said to reduce joint inflammation, omega-3 fatty acid supplements have been the focus of many studies attempting to validate its effectiveness in treating rheumatoid arthritis. According to a large body of research in the area, omega-3 fatty acid supplements are clearly effective in reducing the symptoms associated with rheumatoid arthritis, such as joint tenderness and stiffness. In some cases, a reduction in the amount of medication needed by rheumatoid arthritis patients has been noted.

More research needs to be done to substantiate the effectiveness of omega-3 fatty acids in treating eating disorders, attention deficit disorder, and depression. Some studies have indicated, for example, that children with behavioral problems and attention deficit disorder have lower than normal amounts of omega-3 fatty acids in their bodies. However, until there is more data in these very important areas of research, a conservative approach should be taken, specially when making changes to a child's diet. Parents should to talk to their child's pediatrician to ascertain if adding more omega-3 fatty acids to their child's diet is appropriate. In addition, parents should take special care to avoid feeding their children fish high in mercury. A food list containing items rich in omega-3 fatty acids can be obtained from a licensed dietitian.

Mercury Levels and Concerns About Safety
A great deal of media attention has been focused on the high mercury levels found in some types of fish. People concerned about fish consumption and mercury levels can review public releases on the subject issued by the U. S. Food and Drug Administration and the Environmental Protection Agency. Special precautions exist for children and pregnant or breastfeeding women. They are advised to avoid shark, mackerel, swordfish, and tilefish. However, both the U.S. Food and Drug Administration and the Environmental Protection Agency emphasis the importance of dietary fish. Fish, they caution, should not be eliminated from the diet. In fact, Robert Oh, M.D., stated in his 2005 article, which was published in The Journal of the American Board of Family Practice "With the potential health benefits of fish, women of childbearing age should be encouraged to eat 1 to 2 low-mercury fish meals per week."

Other concerns regarding fish safety have also been reported. In 2004, Hites and colleagues assessed organic contaminants n salmon in an article published in Science. Their conclusion that farmed salmon had higher concentrations of polychlorinated biphenyls than wild salmon prompted public concerns and a response from the American Cancer Society. Farmed fish in Europe was found to have higher levels of mercury than farmed salmon in North and South America; however, the American Cancer Society reminded the public that the "levels of toxins Hites and his colleagues found in the farmed salmon were still below what the U. S. Food and Drug Administration, which regulates food, considers hazardous." The American Cancer Society still continues to promote a healthy, varied diet, which includes fish as a food source.

Recommended Dosage
The AHA recommends that people eat two servings of fish, such as tuna or salmon, at least twice a week. A person with coronary heart disease, according to the AHA, should consume 1 gram of omega-3 fatty acids daily through food intake, most preferably through the consumption of fatty fish. The AHA also states that "people with elevated triglycerides may need 2 to 4 grams of EPA and DHA per day provided as a supplement," which is available in liquid orcapsule form. Ground or cracked flaxseed can easily be incorporated into a person's diet by sprinkling it over salads, soup, and cereal.

Sources differ, but here are some general examples:

* 3 ounces of pickled herring = 1.2 grams of omega-3 fatty acids
* 3 ounces of salmon = 1.3 grams of omega-3 fatty acids
* 3 ounces of halibut = 1.0 grams of omega-3 fatty acids
* 3 ounces of mackerel = 1.6 grams of omega-3 fatty acids
* 1 1/2 teaspoons of flaxseeds = 3 grams of omega-3 fatty acids

Precautions
In early 2004, the U.S. Food and Drug Administration, along with the the Environmental Protection Agency, issued a statement that women who are or may be pregnant, as well as breastfeeding mothers and children, should avoid eating some types of fish thought to contain high levels of mercury. Fish that typically contain high levels of mercury are shark, swordfish, and mackerel, whereas shrimp, canned light tuna, salmon, and catfish are generally thought to have low levels of mercury. Because many people engage in fishing as a hobby, women should be sure before they eat any fish caught by friends and family that the local stream or lake is considered low in mercury.

Conflicting information exists whether it is safe for patients with macular degeneration to take omega-3 fatty acids in supplement form. Until more data becomes available, it is better for people with macular degeneration to receive their omega-3 fatty acids from the food they eat.

Side Effects
Fish oil supplements can cause diarrhea and gas. Also, the fish oil capsules tend to have a fishy aftertaste.

Interactions
Although there are no significant drug interactions associated with eating foods containing omega-3 fatty acids, patients who are being treated with blood-thinning medications shouldn't take omega-3 fatty acid supplements without seeking the advice of their physicians. Excessive bleeding could result. For the same reason, some patients who plan to take more than 3 grams of omega-3 fatty acids in supplement form should first seek the approval of their physicians.

You want to increase your overall health and energy level. You want to prevent heart disease, cancer, depression and Alzheimer's. Perhaps you also want to treat rheumatoid arthritis, diabetes, ulcerative colitis, Raynaud's disease and a host of other diseases. One of the most important things you can do for all of these is increase your intake of the omega-3 fats found in Krill Oil and cod liver oil, and reduce your intake of omega-6 fats.

These two types of fat, omega-3 and omega-6, are both essential for human health. However, the typical American consumes far too many omega-6 fats in their diet while consuming very low levels of omega-3. The ideal ratio of omega-6 to omega-3 fats is 1:1. Our ancestors evolved over millions of years on this ratio. Today, though, our ratio of omega-6 to omega-3 averages from 20:1 to 50:1! That spells serious danger for you, and as is now (finally!) being reported throughout even the mainstream health media, lack of omega-3 from Krill Oil is one of the most serious health issues plaguing contemporary society.

The primary sources of omega-6 are corn, soy, canola, safflower and sunflower oil; these oils are overabundant in the typical diet, which explains our excess omega-6 levels. Avoid or limit these oils. Omega-3, meanwhile, is typically found in flaxseed oil, walnut oil, and fish.

By far, the best type of omega-3 fats are those found in that last category, fish. That's because the omega-3 in fish is high in two fatty acids crucial to human health, DHA and EPA. These two fatty acids are pivotal in preventing heart disease, cancer, and many other diseases. The human brain is also highly dependent on DHA - low DHA levels have been linked to depression, schizophrenia, memory loss, and a higher risk of developing Alzheimer's. Researchers are now also linking inadequate intake of these omega-3 fats in pregnant women to premature birth and low birth weight, and to hyperactivity in children.

Sadly, though, eating most fresh fish, whether from the ocean, lakes and streams, or farm-raised, is no longer recommended. Mercury levels in almost all fish have now hit dangerously high levels across the world, and the risk of this mercury to your health now outweighs the fish's omega-3 benefits. However, because fish would otherwise be immensely healthy, I had been searching for a safe source of fish for some time -- and finally discovered one. The Vital Choice Alaskan wild red salmon offered on this site is the one source of salmon or any fish that, via independent lab-testing, I have discovered is safe from mercury and other toxins. In addition to being mercury-free, the Vital Choice Alaskan salmon is loaded with omega-3 with EPA and DHA , is high in antioxidants to help you live longer, and tastes absolutely delicious.

Routine consumption of Krill Oil is another highly recommended method of increasing your omega-3 intake and improving your health, and is also the most convenient for today's busy lifestyles. Krill Oil contains high levels of the best omega-3 fats - those with the EPA and DHA fatty acids - and, as it is in pure form, does not pose the mercury risk of fresh fish.

While I am well-known as a minimalist when it comes to supplements, Krill Oil (in the warm months) and cod liver oil (in the cool months) are "supplements" that I cannot urge you strongly enough to add to your daily diet if you want to prevent disease and increase both the length and quality of your life.

But as with most foods in general, the type (i.e., brand) of Krill Oil/cod liver oil you choose makes all the difference when it comes to aiding your health. Simply put, there are many inferior brands of Krill Oil and cod liver oil on the market that, at best, you'll be throwing your money away on because they have little real benefit, and at worse, can actually cause you harm over time. Purity and potency mean everything when choosing Krill Oil, and there is a wide variance in those factors with brands out.

Vitamin A: What is it?
Vitamin A is a group of compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation (in which a cell becomes part of the brain, muscle, lungs, blood, or other specialized tissue.) [1-5]. Vitamin A helps regulate the immune system, which helps prevent or fight off infections by making white blood cells that destroy harmful bacteria and viruses [1,6-10]. Vitamin A also may help lymphocytes (a type of white blood cell) fight infections more effectively.

Vitamin A promotes healthy surface linings of the eyes and the respiratory, urinary, and intestinal tracts [8]. When those linings break down, it becomes easier for bacteria to enter the body and cause infection. Vitamin A also helps the skin and mucous membranes function as a barrier to bacteria and viruses [9-11].

In general, there are two categories of vitamin A, depending on whether the food source is an animal or a plant.

Vitamin A found in foods that come from animals is called preformed vitamin A. It is absorbed in the form of retinol, one of the most usable (active) forms of vitamin A. Sources include liver, whole milk, and some fortified food products. Retinol can be made into retinal and retinoic acid (other active forms of vitamin A) in the body [1].

Vitamin A that is found in colorful fruits and vegetables is called provitamin A carotenoid. They can be made into retinol in the body. In the United States, approximately 26% of vitamin A consumed by men and 34% of vitamin A consumed by women is in the form of provitamin A carotenoids [1]. Common provitamin A carotenoids found in foods that come from plants are beta-carotene, alpha-carotene, and beta-cryptoxanthin [11]. Among these, beta-carotene is most efficiently made into retinol [1,13-15]. Alpha-carotene and beta-cryptoxanthin are also converted to vitamin A, but only half as efficiently as beta-carotene [1].

Of the 563 identified carotenoids, fewer than 10% can be made into vitamin A in the body [12]. Lycopene, lutein, and zeaxanthin are carotenoids that do not have vitamin A activity but have other health promoting properties [1]. The Institute of Medicine (IOM) encourages consumption of all carotenoid-rich fruits and vegetables for their health-promoting benefits.

Some provitamin A carotenoids have been shown to function as antioxidants in laboratory studies; however, this role has not been consistently demonstrated in humans [1]. Antioxidants protect cells from free radicals, which are potentially damaging by-products of oxygen metabolism that may contribute to the development of some chronic diseases [3,14-15].

What foods provide vitamin A?
Retinol is found in foods that come from animals such as whole eggs, milk, and liver. Most fat-free milk and dried nonfat milk solids sold in the United States are fortified with vitamin A to replace the amount lost when the fat is removed [16]. Fortified foods such as fortified breakfast cereals also provide vitamin A. Provitamin A carotenoids are abundant in darkly colored fruits and vegetables. The 2000 National Health and Nutrition Examination Survey (NHANES) indicated that major dietary contributors of retinol are milk, margarine, eggs, beef liver and fortified breakfast cereals, whereas major contributors of provitamin A carotenoids are carrots, cantaloupes, sweet potatoes, and spinach [17].

Vitamin A in foods that come from animals is well absorbed and used efficiently by the body. Vitamin A in foods that come from plants is not as well absorbed as animal sources of vitamin A. Tables 1 and 2 suggest many sources of vitamin A and provitamin A carotenoids [18].

Table 1: Selected animal sources of vitamin A [18]
Food Vitamin A (IU)* %DV**
Liver, beef, cooked, 3 ounces 27,185 545
Liver, chicken, cooked, 3 ounces 12,325 245
Milk, fortified skim, 1 cup 500 10
Cheese, cheddar, 1 ounce 284 6
Milk, whole (3.25% fat), 1 cup 249 5
Egg substitute, ¼ cup 226 5


Table 2: Selected plant sources of vitamin A (from beta-carotene) [18]
Food Vitamin A (IU)* %DV**
Carrot juice, canned, ½ cup 22,567 450
Carrots, boiled, ½ cup slices 13,418 270
Spinach, frozen, boiled, ½ cup 11,458 230
Kale, frozen, boiled, ½ cup 9,558 190
Carrots, 1 raw (7½ inches) 8,666 175
Vegetable soup, canned, chunky, ready-to-serve, 1 cup 5,820 115
Cantaloupe, 1 cup cubes 5,411 110
Spinach, raw, 1 cup 2,813 55
Apricots with skin, juice pack, ½ cup 2,063 40
Apricot nectar, canned, ½ cup 1,651 35
Papaya, 1 cup cubes 1,532 30
Mango, 1 cup sliced 1,262 25
Oatmeal, instant, fortified, plain, prepared with water, 1 cup 1,252 25
Peas, frozen, boiled, ½ cup 1,050 20
Tomato juice, canned, 6 ounces 819 15
Peaches, canned, juice pack, ½ cup halves or slices 473 10
Peach, 1 medium 319 6
Pepper, sweet, red, raw, 1 ring (3 inches diameter by ¼ inch thick) 313 6

* IU = International Units
** DV = Daily Value. DVs are reference numbers based on the Recommended Dietary Allowances (RDAs). They were developed to help consumers determine if a food contains a lot or a little of a nutrient. The DV for vitamin A is 5,000 IU. Most food labels do not list vitamin A content. The percent DV (%DV) column in the table above indicates the percentage of the DV provided in one serving. A food providing 5% or less of the DV is a low source while a food that provides 10% to 19% of the DV is a good source. A food that provides 20% or more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a healthful diet. For foods not listed in this table, refer to the U.S. Department of Agriculture's Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

What are recommended intakes of vitamin A?
Recommendations for vitamin A are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine (IOM) [1]. DRI is the general term for a set of reference values used for planning and assessing nutrient intake in healthy people. Three important types of reference values included in the DRIs are Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97% to 98%) healthy individuals in each age and gender group [1]. An AI is set when there are insufficient scientific data to establish an RDA. AIs meet or exceed the amount needed to maintain nutritional adequacy in nearly all people. The UL, on the other hand, is the maximum daily intake unlikely to result in adverse health effects [1].

In Table 3, RDAs for vitamin A are listed as micrograms (mcg) of Retinol Activity Equivalents (RAE) to account for the different biological activities of retinol and provitamin A carotenoids [1]. Table 3 also lists RDAs for vitamin A in International Units (IU), which are used on food and supplement labels (1 RAE = 3.3 IU).

Table 3: Recommended Dietary Allowances (RDAs) for vitamin A
Age
(years) Children
(mcg RAE) Males
(mcg RAE) Females
(mcg RAE) Pregnancy
(mcg RAE) Lactation
(mcg RAE)
1-3 300
(1,000 IU)
4-8 400
(1,320 IU)
9-13 600
(2,000 IU)
14-18 900
(3,000 IU) 700
(2,310 IU) 750
(2,500 IU) 1,200
(4,000 IU)
19+ 900
(3,000 IU) 700
(2,310 IU) 770
(2,565 IU) 1,300
(4,300 IU)

Information is insufficient to establish an RDA for vitamin A for infants. AIs have been established based on the amount of vitamin A consumed by healthy infants fed breast milk (Table 4) [1].

Table 4: Adequate Intakes (AIs) for vitamin A for infants
Age (months) Males and females (mcg RAE)
0-6 400 (1,320 IU)
7-12 500 (1,650 IU)

The NHANES III survey (1988-1994) found that most Americans consume recommended amounts of vitamin A [19]. More recent NHANES data (1999-2000) show average adult intakes to be about 3,300 IU per day, which also suggests that most Americans get enough vitamin A [20].

There is no RDA for beta-carotene or other provitamin A carotenoids. The IOM states that consuming 3 mg to 6 mg of beta-carotene daily (equivalent to 833 IU to 1,667 IU vitamin A) will maintain blood levels of beta-carotene in the range associated with a lower risk of chronic diseases [1]. A diet that provides five or more servings of fruits and vegetables per day and includes some dark green and leafy vegetables and deep yellow or orange fruits should provide sufficient beta-carotene and other carotenoids.

When can vitamin A deficiency occur?
Vitamin A deficiency is common in developing countries but rarely seen in the United States. Approximately 250,000 to 500,000 malnourished children in the developing world become blind each year from a deficiency of vitamin A [1]. In the United States, vitamin A deficiency is most often associated with strict dietary restrictions and excess alcohol intake [21]. Severe zinc deficiency, which is also associated with strict dietary limitations, often accompanies vitamin A deficiency. Zinc is required to make retinol binding protein (RBP) which transports vitamin A. Therefore, a deficiency in zinc limits the body's ability to move vitamin A stores from the liver to body tissues [1].

Night blindness is one of the first signs of vitamin A deficiency. In ancient Egypt, it was known that night blindness could be cured by eating liver, which was later found to be a rich source of the vitamin [2]. Vitamin A deficiency contributes to blindness by making the cornea very dry and damaging the retina and cornea [22].

Vitamin A deficiency diminishes the ability to fight infections. In countries where such deficiency is common and immunization programs are limited, millions of children die each year from complications of infectious diseases such as measles [23]. In vitamin A-deficient individuals, cells lining the lungs lose their ability to remove disease-causing microorganisms. This may contribute to the pneumonia associated with vitamin A deficiency [2,6-7].

There is increased interest in early forms of vitamin A deficiency, described as low storage levels of vitamin A that do not cause obvious deficiency symptoms. This mild degree of vitamin A deficiency may increase children's risk of developing respiratory and diarrheal infections, decrease growth rate, slow bone development, and decrease likelihood of survival from serious illness [24-25]. Children in the United States who are considered to be at increased risk for subclinical vitamin A deficiency include:

* toddlers and preschool age children;
* children living at or below the poverty level;
* children with inadequate health care or immunizations;
* children living in areas with known nutritional deficiencies;
* recent immigrants or refugees from developing countries with high incidence of vitamin A deficiency or measles; and
* children with diseases of the pancreas, liver, or intestines, or with inadequate fat digestion or absorption.

A deficiency can occur when vitamin A is lost through chronic diarrhea and through an overall inadequate intake, as is often seen with protein-energy malnutrition. Low blood retinol concentrations indicate depleted levels of vitamin A. This occurs with vitamin A deficiency but also can result from an inadequate intake of protein, calories, and zinc, since these nutrients are needed to make RBP [1]. Iron deficiency can also affect vitamin A metabolism, and iron supplements provided to iron-deficient individuals may improve body stores of vitamin A and iron [1].

Excess alcohol intake depletes vitamin A stores. Also, diets high in alcohol often do not provide recommended amounts of vitamin A [1]. It is very important for people who consume excessive amounts of alcohol to include good sources of vitamin A in their diets. Vitamin A supplements may not be recommended for individuals who abuse alcohol, however, because their livers may be more susceptible to potential toxicity from high doses of vitamin A [26]. A medical doctor will need to evaluate this situation and determine the need for vitamin A supplements.

Who may need extra vitamin A to prevent a deficiency?
Vitamin A deficiency rarely occurs in the United States, but the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) recommend vitamin A administration for all children diagnosed with measles in communities where vitamin A deficiency is a serious problem and where death from measles is greater than 1%. In 1994, the American Academy of Pediatrics recommended vitamin A supplements for two subgroups of children likely to be at high risk for subclinical vitamin A deficiency: children aged 6 months to 24 months who are hospitalized with measles, and hospitalized children older than 6 months [27].

Fat malabsorption can result in diarrhea and prevent normal absorption of vitamin A. Over time this may result in vitamin A deficiency. Those conditions include:

* Celiac disease:
Often referred to as sprue, celiac disease is a genetic disorder. People with celiac disease become sick when they eat a protein called gluten found in wheat and some other grains. In celiac disease, gluten can trigger damage to the small intestine, where most nutrient absorption occurs. Approximately 30% to 60% of people with celiac disease have gastrointestinal-motility disorders such as diarrhea [28].They must follow a gluten-free diet to avoid malabsorption and other symptoms.
* Crohn's disease:
This inflammatory bowel disease affects the small intestine. People with Crohn's disease often experience diarrhea, fat malabsorption, and malnutrition [29].
* Pancreatic disorders:
Because the pancreas secretes enzymes that are important for fat absorption, pancreatic disorders often result in fat malabsorption [30-31]. Without these enzymes, it is difficult to absorb fat. Many people with pancreatic disease take pancreatic enzymes in pill form to prevent fat malabsorption and diarrhea.

Healthy adults usually have a reserve of vitamin A stored in their livers and should not be at risk of deficiency during periods of temporary or short-term fat malabsorption. Long-term problems absorbing fat, however, may result in deficiency. In these instances physicians may recommend additional vitamin A [9].

Vegetarians who do not consume eggs and dairy foods need provitamin A carotenoids to meet their need for vitamin A [1]. They should include a minimum of five servings of fruits and vegetables in their daily diet and regularly choose dark green leafy vegetables and orange and yellow fruits to consume recommended amounts of vitamin A.

What are some current issues and controversies about vitamin A?
Vitamin A, beta carotene, and cancer
Dietary intake studies suggest an association between diets rich in beta-carotene and vitamin A and a lower risk of many types of cancer [32]. A higher intake of green and yellow vegetables or other food sources of beta carotene and/or vitamin A may decrease the risk of lung cancer [2,33-34]. However, a number of studies that tested the role of beta-carotene supplements in cancer prevention did not find them to protect against the disease. In the Alpha-Tocopherol Beta-Carotene (ATBC) Cancer Prevention Study, more than 29,000 men who regularly smoked cigarettes were randomized to receive 20 mg beta-carotene alone, 50 mg alpha-tocopherol alone, supplements of both, or a placebo for 5 to 8 years. Incidence of lung cancer was 18% higher among men who took the beta-carotene supplement. Eight percent more men in this group died, as compared to those receiving other treatments or placebo [35]. Similar results were seen in the Carotene and Retinol Efficacy Trial (CARET), a lung cancer chemoprevention study that provided subjects with supplements of 30 mg beta-carotene and 25,000 IU retinyl palmitate (a form of vitamin A) or a placebo. This study was stopped after researchers discovered that subjects receiving beta-carotene had a 46% higher risk of dying from lung cancer [36-37].

The IOM states that "beta-carotene supplements are not advisable for the general population," although they also state that this advice "does not pertain to the possible use of supplemental beta-carotene as a provitamin A source for the prevention of vitamin A deficiency in populations with inadequate vitamin A" [1].

Vitamin A and osteoporosis
Osteoporosis, a disorder characterized by porous and weak bones, is a serious health problem for more than 10 million Americans, 80% of whom are women. Another 18 million Americans have decreased bone density which precedes the development of osteoporosis. Many factors increase the risk for developing osteoporosis, including being female, thin, inactive, at advanced age, and having a family history of osteoporosis. An inadequate dietary intake of calcium, cigarette smoking, and excessive intake of alcohol also increase the risk [38-40].

Researchers are now examining a potential new risk factor for osteoporosis: an excess intake of vitamin A. Animal, human, and laboratory research suggests an association between greater vitamin A intake and weaker bones [40-41]. Worldwide, the highest incidence of osteoporosis occurs in northern Europe, a population with a high intake of vitamin A [42]. However, decreased biosynthesis of vitamin D associated with lower levels of sun exposure in this population may also contribute to this finding.

One small study of nine healthy individuals in Sweden found that the amount of vitamin A in one serving of liver may impair the ability of vitamin D to promote calcium absorption [43]. To further test the association between excess dietary intakes of vitamin A and increased risk for hip fractures, researchers in Sweden compared bone mineral density and retinol intake in approximately 250 women with a first hip fracture to 875 age-matched controls. They found that a dietary retinol intake greater than 1,500 mcg/day (more than twice the recommended intake for women) was associated with reduced bone mineral density and increased risk of hip fracture as compared to women who consumed less than 500 mcg/day [44].

This issue was also examined by researchers with the Nurses Health Study, who looked at the association between vitamin A intake and hip fractures in over 72,000 postmenopausal women. Women who consumed the most vitamin A in foods and supplements (3,000 mcg or more per day as retinol equivalents, which is over three times the recommended intake) had a significantly increased risk of experiencing a hip fracture as compared to those consuming the least amount (less than 1,250 mcg/day). The effect was lessened by use of estrogens. These observations raise questions about the effect of retinol because retinol intakes greater than 2,000 mcg/day were associated with an increased risk of hip fracture as compared to intakes less than 500 mcg [45].

A longitudinal study in more than 2,000 Swedish men compared blood levels of retinol to the incidence of fractures in men. The investigators found that the risk of fractures was greatest in men with the highest blood levels of retinol (more than 75 mcg per deciliter [dL]). Men with blood retinol levels in the 99th percentile (greater than 103 mcg per dL) had an overall risk of fracture that exceeded the risk among men with lower levels of retinol by a factor of seven [46]. High vitamin A intake, however, does not necessarily equate to high blood levels of retinol. Age, gender, hormones, and genetics also influence these levels. Researchers did not find any association between blood levels of beta-carotene and risk of hip fracture. Researchers' findings, which are consistent with the results of animal, in vitro (laboratory), and epidemiologic studies, suggest that intakes above the UL, or approximately two times that of the RDA for vitamin A, may pose subtle risks to bone health that require further study.

The Centers for Disease Control and Prevention (CDC) reviewed data from NHANES III (1988-94) to determine whether there was any association between bone mineral density and blood levels of retinyl esters, a form of vitamin A [47]. No significant associations between blood levels of retinyl esters and bone mineral density in 5,800 subjects were found.

There is no evidence of an association between beta-carotene intake, especially from fruits and vegetables, and increased risk of osteoporosis. Current evidence points to a possible association with vitamin A as retinol only. If you have specific questions regarding your intake of vitamin A and risk of osteoporosis, discuss this information with your physician or other qualified healthcare provider to determine what's best for your personal health.

What are the health risks of too much vitamin A?
Hypervitaminosis A refers to high storage levels of vitamin A in the body that can lead to toxic symptoms. There are four major adverse effects of hypervitaminosis A: birth defects, liver abnormalities, reduced bone mineral density that may result in osteoporosis (see the previous section), and central nervous system disorders [1,48-49].

Toxic symptoms can also arise after consuming very large amounts of preformed vitamin A over a short period of time. Signs of acute toxicity include nausea and vomiting, headache, dizziness, blurred vision, and muscular uncoordination [1,48-49]. Although hypervitaminosis A can occur when large amounts of liver are regularly consumed, most cases result from taking excess amounts of the nutrient in supplements.

The IOM has established Tolerable Upper Intake Levels (ULs) for vitamin A that apply to healthy populations [1]. The UL was established to help prevent the risk of vitamin A toxicity. The risk of adverse health effects increases at intakes greater than the UL. The UL does not apply to malnourished individuals receiving vitamin A either periodically or through fortification programs as a means of preventing vitamin A deficiency. It also does not apply to individuals being treated with vitamin A by medical doctors for diseases such as retinitis pigmentosa.

Table 5: Tolerable Upper Intake Levels (ULs) for retinol
Age
(years) Children
(mcg) Males
(mcg) Females
(mcg) Pregnancy
(mcg) Lactation
(mcg)
0-1 600
(2,000 IU)
1-3 600
(2,000 IU)
4-8 900
(3,000 IU)
9-13 1,700 (5610 IU)
14-18 2,800 (9,240 IU) 2,800 (9,240 IU) 2,800 (9,240 IU) 2,800 (9,240 IU)
19+ 3,000 (10,000 IU) 3,000 (10,000 IU) 3,000 (10,000 IU) 3,000 (10,000 IU)


Retinoids are compounds that are chemically similar to vitamin A. Over the past 15 years, synthetic retinoids have been prescribed for acne, psoriasis, and other skin disorders [50]. Isotretinoin (Roaccutane® or Accutane®) is considered an effective anti-acne therapy. At very high doses, however, it can be toxic, which is why this medication is usually saved for the most severe forms of acne [51-53]. The most serious consequence of this medication is birth defects. It is extremely important for sexually active females who may become pregnant and who take these medications to use an effective method of birth control. Women of childbearing age who take these medications are advised to undergo monthly pregnancy tests to make sure they are not pregnant.

What are the health risks of too many carotenoids?
Provitamin A carotenoids such as beta-carotene are generally considered safe because they are not associated with specific adverse health effects. Their conversion to vitamin A decreases when body stores are full. A high intake of provitamin A carotenoids can turn the skin yellow, but this is not considered dangerous to health.

Clinical trials that associated beta-carotene supplements with a greater incidence of lung cancer and death in current smokers raise concerns about the effects of beta-carotene supplements on long-term health; however, conflicting studies make it difficult to interpret the health risk. For example, the Physicians Health Study compared the effects of taking 50 mg beta-carotene every other day to a placebo in over 22,000 male physicians and found no adverse health effects [54]. Also, a trial that tested the ability of four different nutrient combinations to help prevent the development of esophageal and gastric cancers in 30,000 men and women in China suggested that after five years those participants who took a combination of beta-carotene, selenium, and vitamin E had a 13% reduction in cancer deaths [55]. In one lung cancer trial, men who consumed more than 11 grams/day of alcohol (approximately one drink per day) were more likely to show an adverse response to beta-carotene supplements [1], which may suggest a potential relationship between alcohol and beta-carotene.

The IOM did not set ULs for carotene or other carotenoids. Instead, it concluded that beta-carotene supplements are not advisable for the general population. As stated earlier, however, they may be appropriate as a provitamin A source for the prevention of vitamin A deficiency in specific populations [1].

Vitamin A intakes and healthful diets
According to the 2005 Dietary Guidelines for Americans, "Nutrient needs should be met primarily through consuming foods. Foods provide an array of nutrients and other compounds that may have beneficial effects on health. In certain cases, fortified foods and dietary supplements may be useful sources of one or more nutrients that otherwise might be consumed in less than recommended amounts. However, dietary supplements, while recommended in some cases, cannot replace a healthful diet [56]." For more information about building a healthful diet, refer to the Dietary Guidelines for Americans (http://www.health.gov/dietaryguidelines/dga2005/document/pdf/DGA2005.pdf) and the U.S. Department of Agriculture's food guidance system (My Pyramid; http://www.mypyramid.gov).

Reference: http://ods.od.nih.gov/factsheets/vitamina.asp

What is vitamin D?
Vitamin D is a fat soluble vitamin that is found in food and can also be made in your body after exposure to ultraviolet (UV) rays from the sun. Sunshine is a significant source of vitamin D because UV rays from sunlight trigger vitamin D synthesis in the skin [1-2].

Vitamin D exists in several forms, each with a different level of activity. Calciferol is the most active form of vitamin D. Other forms are relatively inactive in the body. The liver and kidney help convert vitamin D to its active hormone form [3]. Once vitamin D is produced in the skin or consumed in food, it requires chemical conversion in the liver and kidney to form 1,25 dihydroxyvitamin D, the physiologically active form of vitamin D. Active vitamin D functions as a hormone because it sends a message to the intestines to increase the absorption of calcium and phosphorus [3].

The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus [3-4]. By promoting calcium absorption, vitamin D helps to form and maintain strong bones. Vitamin D also works in concert with a number of other vitamins, minerals, and hormones to promote bone mineralization. Without vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults, two forms of skeletal diseases that weaken bones [5-6].

Research also suggests that vitamin D may help maintain a healthy immune system and help regulate cell growth and differentiation, the process that determines what a cell is to become [3,7,8].

What are the sources of vitamin D?
Food Sources

Fortified foods are common sources of vitamin D [4]. In the 1930s, rickets was a major public health problem in the United States (U.S.). A milk fortification program was implemented to combat rickets, and it nearly eliminated this disorder in the U.S. [4,9]. About 98% to 99% of the milk supply in the U.S. is fortified with 10 micrograms (ìg) (equal to 400 International Units or IU) of vitamin D per quart. One cup of vitamin D fortified milk supplies one-half of the recommended daily intake for adults between the ages of 19 and 50, one-fourth of the recommended daily intake for adults between the ages of 51 and 70, and approximately 15% of the recommended daily intake for adults age 71 and over.

Although milk is fortified with vitamin D, dairy products made from milk, such as cheese and ice creams, are generally not fortified with vitamin D and contain only small amounts. Some ready-to-eat breakfast cereals may be fortified with vitamin D, often at a level of 10% to 15% of the Daily Value*. There are only a few commonly consumed foods that are good sources of vitamin D [4]. Suggested dietary sources of vitamin D are listed in Table 1.

Table 1: Selected food sources of vitamin D [10-12]
Food International Units(IU) per serving Percent DV*
Cod liver oil, 1 Tablespoon 1,360 340
Salmon, cooked, 3½ ounces 360 90
Mackerel, cooked, 3½ ounces 345 90
Tuna fish, canned in oil, 3 ounces 200 50
Sardines, canned in oil, drained, 1¾ ounces 250 70
Milk, nonfat, reduced fat, and whole, vitamin D fortified, 1 cup 98 25
Margarine, fortified, 1 Tablespoon 60 15
Pudding, prepared from mix and made with vitamin D fortified milk, ½ cup 50 10
Ready-to-eat cereals fortified with 10% of the DV for vitamin D, ¾ cup to 1 cup servings (servings vary according to the brand) 40 10
Egg, 1 whole (vitamin D is found in egg yolk) 20 6
Liver, beef, cooked, 3½ ounces 15 4
Cheese, Swiss, 1 ounce 12 4

*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for vitamin D is 400 IU (10 μg) for adults. Most food labels do not list vitamin D content unless a food has been fortified with this nutrient. The percent DV (%DV) listed on the table above tells you the percent of the DV provided in one serving. A food providing 5% of the DV or less is a low source while a food that provides 10-19% of the DV is a good source and a food that provides 20% or more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a healthful diet. For foods not listed in this table, please refer to the U.S. Department of Agriculture’s Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

Sun exposure
Sun exposure is perhaps the most important source of vitamin D because exposure to sunlight provides most humans with their vitamin D requirement [13]. UV rays from the sun trigger vitamin D synthesis in skin [13-14]. Season, geographic latitude, time of day, cloud cover, smog, and sunscreen affect UV ray exposure and vitamin D synthesis [14]. For example, sunlight exposure from November through February in Boston is insufficient to produce significant vitamin D synthesis in the skin. Complete cloud cover halves the energy of UV rays, and shade reduces it by 60%. Industrial pollution, which increases shade, also decreases sun exposure and may contribute to the development of rickets in individuals with insufficient dietary intake of vitamin D [15]. Sunscreens with a sun protection factor (SPF) of 8 or greater will block UV rays that produce vitamin D, but it is still important to routinely use sunscreen to help prevent skin cancer and other negative consequences of excessive sun exposure. An initial exposure to sunlight (10 -15 minutes) allows adequate time for Vitamin D synthesis and should be followed by application of a sunscreen with an SPF of at least 15 to protect the skin. Ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen is usually sufficient to provide adequate vitamin D [14]. It is very important for individuals with limited sun exposure to include good sources of vitamin D in their diet.

What is the recommended intake for vitamin D?
Recommendations for vitamin D are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine (IOM) of the National Academy of Sciences [4]. Dietary Reference Intakes is the general term for a set of reference values used for planning and assessing nutrient intake for healthy people. Three important types of reference values included in the DRIs are Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average daily intake that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in each age and gender group [4]. An AI is set when there is insufficient scientific data available to establish a RDA. AIs meet or exceed the amount needed to maintain a nutritional state of adequacy in nearly all members of a specific age and gender group. The UL, on the other hand, is the maximum daily intake unlikely to result in adverse health effects [4].

The IOM determined there was insufficient scientific information to establish a RDA for vitamin D. Instead, the recommended intake is listed as an Adequate Intake (AI), which represents the daily vitamin D intake that should maintain bone health and normal calcium metabolism in healthy people.

AIs for vitamin D may be listed on food and dietary supplement labels as either micrograms (μg) or International Units (IU). The biological activity of 1 μg vitamin D is equal to 40 IUs [4]. AIs for vitamin D for infants, children, and adults, are listed in table 2 in micrograms and IUs [4].

Table 2: Adequate Intake for vitamin D for infants, children, and adults [4]
Age Children
(μg/day) Men
(μg/day) Women
(μg/day) Pregnancy
(μg/day) Lactation
(μg/day)
Birth to 13 years 5
(=200 IU)
14 to 18 years 5
(=200 IU) 5
(=200 IU) 5
(=200 IU) 5
(=200 IU)
19 to 50 years 5
(=200 IU) 5
(=200 IU) 5
(=200 IU) 5
(=200 IU)
51 to 70 years 10
(=400 IU) 10
(=400 IU)
71+ years 15
(=600 IU) 15
(=600 IU)

According to the IOM's report on the Dietary Reference Intakes for vitamin D, food consumption data suggest that median intakes of vitamin D for both younger and older women are below current recommendations [4]. Median intake refers to a statistical mid-point. Half of the population surveyed consumed more than the median intake while half consumed less. In this case, data suggest that more than 50% of younger and older women are not consuming recommended amounts of vitamin D.

In 2002, the vitamin D intakes of 1,546 non-Hispanic African American women and 1,426 non-Hispanic white women of reproductive age (15 to 49 years) were estimated by analyzing intake of milk and fortified cereals, two common dietary sources of vitamin D [16]. Blood levels of vitamin D were also examined in these groups. Data examined were from the National Health and Nutrition Examination Survey (NHANES) III survey, which interviewed people from randomly selected households all across the U.S. The prevalence of hypovitaminosis D, a term used to describe low blood levels of vitamin D, was 42.4% among African American women and 4.2% among white women. In both groups, blood levels of vitamin D were higher when milk or fortified cereals were consumed more than 3 times per week. Among African American women, the risk of hypovitaminosis D decreased as milk and fortified cereal intake increased. These numbers suggest that large numbers of African American women may not consume recommended amounts of vitamin D. More frequent intake of vitamin D fortified milk and fortified cereals may help prevent hypovitaminosis D in this group.

When can vitamin D deficiency occur?
# Nutrient deficiencies are usually the result of dietary inadequacy, impaired absorption and utilization, increased requirement, or increased excretion (loss). A deficiency of vitamin D can occur [9]: when usual intake is below recommended levels
# when there is limited exposure to sunlight
# when the kidney cannot convert vitamin D to its active hormone form
# when someone cannot adequately absorb vitamin D from the digestive tract

Vitamin D deficient diets are associated with milk allergy, lactose intolerance, and strict vegetarianism. Infants fed only breast milk also receive insufficient amounts of vitamin D unless they also receive appropriate levels of vitamin D supplementation [17].

The classic vitamin D deficiency diseases are rickets and osteomalacia. In children, vitamin D deficiency causes rickets. Rickets is a bone disease characterized by a failure to properly mineralize bone tissue. Rickets results in soft bones and skeletal deformities [15]. Rickets was first described in the mid-17th century by British researchers [15,18]. In the late 19th and early 20th century, German physicians noted that consuming 1 to 3 teaspoons (3 teaspoons is equal to 1 tablespoon) of cod liver oil per day could reverse rickets [18]. The most common causes of rickets are vitamin D deficiency from a vitamin D deficient diet, lack of sunlight, or both. The recommendation to fortify milk with vitamin D made rickets a rare disease in the U.S. for many years. However, rickets has recently reemerged, in particular among African American infants and children [15,18]. In 2003, a report from Memphis, Tennessee, described 21 cases of rickets among infants, 20 of whom were African-American [18].

Prolonged exclusive breastfeeding without vitamin D supplementation is one of the most significant causes of the reemergence of rickets. Additional causes include extensive use of sunscreens and increased use of day-care, resulting in decreased outdoor activity and sun exposure among children [15,18].

Rickets is more prevalent among immigrants from Asia, Africa, and Middle Eastern countries for a variety of reasons [15]. Among immigrants, vitamin D deficiency has been associated with iron deficiency, leading researchers to question whether or not iron deficiency may impair vitamin D metabolism [15]. Immigrants from these regions are also more likely to follow dress codes that limit sun exposure. In addition, darker pigmented skin converts UV rays to vitamin D less efficiently than lighter skin [15].

In adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones [5-6,9]. Symptoms of bone pain and muscle weakness may indicate vitamin D deficiency, but symptoms may be subtle and go undetected in the initial stages. A deficiency is accurately diagnosed by measuring the concentration of a specific form of vitamin D in blood [9,14].

Who may need extra vitamin D to prevent a deficiency?
It can be difficult to obtain enough vitamin D from natural food sources. For many people, consuming vitamin D fortified foods and adequate sunlight exposure are essential for maintaining a healthy vitamin D status. In some groups, dietary supplements may be needed to meet the daily need for vitamin D.

Infants who are exclusively breastfed
In infants, vitamin D requirements cannot be met by human (breast) milk alone [4,19], which usually provides approximately 25 IU vitamin D per liter [20]. Sunlight is a potential source of vitamin D for infants, but the American Academy of Pediatrics (AAP) advises that infants be kept out of direct sunlight and wear protective clothing and sunscreen when exposed to sunlight [21]. The American Academy of Pediatrics (AAP) recommends a daily supplement of 200 IU vitamin D for breastfed infants beginning within the first 2 months of life unless they are weaned to receive at least 500 ml (about 2 cups) per day of vitamin D-fortified formula [20]. Children and adolescents who are not routinely exposed to sunlight and do not consume at least 2, 8-fluid ounce servings of vitamin D-fortified milk per day are also at higher risk of vitamin D deficiency and may need a dietary supplement containing 200 IU vitamin D [20].

Formula fed infants usually consume recommended amounts of vitamin D because the 1980 Infant Formula Act requires that infant formulas be fortified with vitamin D. The minimal level of fortification required is 40 IU vitamin D per 100 calories of formula. The maximum level of vitamin D fortification allowed is 100 IU per 100 calories of formula [22]. This range of fortification produces a standard 20 calorie per ounce formula providing between 265 and 660 IU vitamin D per liter.

Older adults
Americans age 50 and older are believed to be at increased risk of developing vitamin D deficiency [14]. As people age, skin cannot synthesize vitamin D as efficiently and the kidney is less able to convert vitamin D to its active hormone form [4,23-26]. It is estimated that as many as 30% to 40% of older adults with hip fractures are vitamin D insufficient [13]. Therefore, older adults may benefit from supplemental vitamin D.

Persons with limited sun exposure
Homebound individuals, people living in northern latitudes such as in New England and Alaska, women who wear robes and head coverings for religious reasons, and individuals working in occupations that prevent sun exposure are unlikely to obtain much vitamin D from sunlight. It is important for people with limited sun exposure to consume recommended amounts of vitamin D in their diets or consider vitamin D supplementation [27-29].

Persons with greater skin melanin content
Melanin is the pigment that gives skin its color. Greater amounts of melanin result in darker skin. The high melanin content in darker skin reduces the skin's ability to produce vitamin D from sunlight. It is very important for African Americans and other populations with dark-pigmented skin to consume recommended amounts of vitamin D. Some studies suggest that older adults, especially women, in these groups are at even higher risk of vitamin D deficiency [16,30]. Individuals with darkly pigmented skin who are unable to get adequate sun exposure and/or consume recommended amounts of vitamin D may benefit from a vitamin D supplement.

Persons with fat malabsorption
As a fat soluble vitamin, vitamin D requires some dietary fat for absorption. Individuals who have a reduced ability to absorb dietary fat may require vitamin D supplements [31]. Symptoms of fat malabsorption include diarrhea and oily stools [31]. Fat malabsorption is associated with a variety of medical conditions [9]:

Pancreatic enzyme deficiencyis characterized by insufficient secretion of pancreatic enzymes. Pancreatic enzymes are essential for fat absorption, and a deficiency of these enzymes can result in fat malabsorption.

Crohn's Disease is an inflammatory bowel disease that affects the small intestines. People with Crohn's disease often experience diarrhea and fat malabsorption.

Cystic Fibrosis (CF) is a hereditary disorder that causes the body to secrete a thick, sticky mucus. This mucus clogs the pancreas and lungs. People with CF often experience fat malabsorption.

Sprue, often referred to as Celiac Disease (CD), is a genetic disorder. People with CD are intolerant to a protein called gluten. In CD, gluten can trigger damage to the small intestines, where most nutrient absorption occurs. People with CD often experience fat malabsorption. They need to follow a gluten free diet to avoid malabsorption and other symptoms of CD.

Liver disease includes a wide variety of disorders that impair liver function. Some people with liver disease experience fat malabsorption.

Surgical removal of part or all of the stomach or intestines can impair digestion and absorption of many nutrients. Fat malabsorption can occur after this type of surgery.


What are some current issues and controversies about vitamin D?
Vitamin D and osteoporosis:
It is estimated that over 25 million adults in the United States have, or are at risk of developing, osteoporosis [32]. Osteoporosis is a disease characterized by fragile bones, and it significantly increases the risk of bone fractures. Osteoporosis is most often associated with inadequate calcium intake. However, a deficiency of vitamin D also contributes to osteoporosis by reducing calcium absorption [33]. While rickets and osteomalacia are extreme examples of vitamin D deficiency, osteopororsis is an example of a long-term effect of vitamin D insufficiency [34]. Adequate storage levels of vitamin D help keep bones strong and may help prevent osteoporosis in older adults, in non-ambulatory individuals (those who have difficulty walking and exercising), in post-menopausal women, and in individuals on chronic steroid therapy [35].

Researchers know that normal bone is constantly being remodeled, a process that describes the breakdown and rebuilding of bone. During menopause, the balance between these two systems changes, resulting in more bone being broken down or resorbed than rebuilt. Hormone therapy (HT) with sex hormones such as estrogen and progesterone may delay the onset of osteoporosis. However, some medical groups and professional societies such as the American College of Obstetricians and Gynecologists, The North American Menopause Society, and The American Society for Bone and Mineral Research recommend that postmenopausal women consider using other agents to slow or stop bone-resorption because of the potential adverse health effects of HT [36-38].

Vitamin D deficiency, which is often seen in post-menopausal women and older Americans [4], has been associated with greater incidence of hip fractures [39-41]. In a review of women with osteoporosis hospitalized for hip fractures, 50 percent were found to have signs of vitamin D deficiency [35]. Daily supplementation with 20 μg (800 IU) of vitamin D may reduce the risk of osteoporotic fractures in elderly populations with low blood levels of vitamin D [42]. The Decalyos II study examined the effect of combined calcium and vitamin D supplementation in a group of elderly women who were able to walk indoors with a cane or walker. The women were studied for two years, and results suggested that such supplementation could reduce the risk of hip fractures in this population [43].

All women are encouraged to consult with a physician about their need for vitamin D supplementation as part of an overall plan to prevent and/or treat osteoporosis.

Vitamin D and cancer:
Laboratory, animal, and epidemiologic evidence suggests that vitamin D may be protective against some cancers. Epidemiologic studies suggest that a higher dietary intake of calcium and vitamin D, and/or sunlight-induced vitamin D synthesis, correlates with lower incidence of cancer [44-51]. In fact, for over 60 years researchers have observed an inverse association between sun exposure and cancer mortality [33]. The inverse relationship between higher vitamin D levels in blood and lower cancer risk in humans is best documented for colon and colorectal cancers [44-50]. Vitamin D emerged as a protective factor in a study of over 3,000 adults (96% of whom were men) who underwent a colonoscopy between 1994 and 1997 to look for polyps or lesions in the colon. About 10% of the group was found to have at least one advanced neoplastic (cancerous) lesion in the colon. There was a significantly lower risk of advanced cancerous lesions among those with the highest vitamin D intake [52].

Additional well-designed clinical trials need to be conducted to determine whether vitamin D deficiency increases cancer risk, or if an increased intake of vitamin D is protective against some cancers. Until such trials are conducted, it is premature to advise anyone to take vitamin D supplements for cancer prevention.

Vitamin D and steroids:
Corticosteroid medications such as prednisone are often prescribed to reduce inflammation from a variety of medical problems. These medicines may be essential for medical treatment, but they have potential side effects, including decreased calcium absorption [53-55]. There is some evidence that steroids may also impair vitamin D metabolism, further contributing to the loss of bone and development of osteoporosis associated with long term use of steroid medications [54]. One study demonstrated that patients who received 0.25 μg of active vitamin D and 1000 mg calcium per day in addition to corticosteroid therapy after a kidney transplant avoided rapid bone loss commonly associated with post-transplant therapy [55]. For these reasons, individuals on chronic steroid therapy should consult with a qualified health care professional about the need to increase vitamin D intake through diet and/or dietary supplements.

Vitamin D and Alzheimer's disease:
Alzheimer's disease is associated with an increased risk of hip fractures [56]. This may be because many Alzheimer's patients are homebound, frequently sunlight deprived, and older. With aging, less vitamin D is converted to its active form [4]. One study of women with Alzheimer's disease found that decreased bone mineral density was associated with a low intake of vitamin D and inadequate sunlight exposure [57]. Physicians should evaluate the need for vitamin D supplementation as part of an overall treatment plan for adults with Alzheimer's disease.

Vitamin D and caffeine:
High caffeine intake may accelerate bone loss. Caffeine may inhibit vitamin D receptors, thus limiting absorption of vitamin D and decreasing bone mineral density. A study found that elderly postmenopausal women who consumed more than 300 milligrams per day of caffeine (which is equivalent to approximately 18 oz of caffeinated coffee) lost more bone in the spine than women who consumed less than 300 milligrams per day [58]. However, there is also evidence that increasing calcium intake (by, for example, adding milk to coffee) can counteract any potential negative effect that caffeine may have on bone loss. More evidence is needed before health professionals can confidently advise adults to decrease caffeine intake as a means of preventing osteoporosis.

What are the health risks of too much vitamin D?
Vitamin D toxicity can cause nausea, vomiting, poor appetite, constipation, weakness, and weight loss [59]. It can also raise blood levels of calcium [6], causing mental status changes such as confusion. High blood levels of calcium also can cause heart rhythm abnormalities. Calcinosis, the deposition of calcium and phosphate in the body's soft tissues such as the kidney, can also be caused by vitamin D toxicity [4].

Sun exposure is unlikely to result in vitamin D toxicity [60]. Diet is also unlikely to cause vitamin D toxicity, unless large amounts of cod liver oil are consumed. Vitamin D toxicity is much more likely to occur from high intakes of vitamin D in supplements. The Food and Nutrition Board of the Institute of Medicine has set the tolerable upper intake level (UL) for vitamin D at 25 μg (1,000 IU) for infants up to 12 months of age and 50 μg (2,000 IU) for children, adults, pregnant, and lactating women [4]. Long term intakes above the UL increase the risk of adverse health effects. Upper intake levels for vitamin D are listed in micrograms and International Units for infants, children, and adults in Table 3 [4].

Table 3: Tolerable Upper Intake Levels for vitamin D for infants, children, and adults [4]
Age Men
(μg/day) Women
(μg/day) Pregnancy
(μg/day) Lactation
(μg/day)
0 to 12 months 25
(=1,000 IU) 25
(=1,000 IU)
1 to 13 years 50
(=2,000 IU) 50
(=2,000 IU)
14 to 18 years 50
(=2,000 IU) 50
(=2,000 IU) 50
(=2,000 IU) 50
(=2,000 IU)
19+ years 50
(=2,000 IU) 50
(=2,000 IU) 50
(=2,000 IU) 50
(=2,000 IU)


Selecting a healthful diet
As the 2000 Dietary Guidelines for Americans state, "Different foods contain different nutrients and other healthful substances. No single food can supply all the nutrients in the amounts you need" [61]. For more information about building a healthful diet, refer to the Dietary Guidelines for Americans [61] http://www.health.gov/dietaryguidelines and the US Department of Agriculture's Food Guide Pyramid [62] http://www.usda.gov/cnpp/pyramid2.htm.

This Fact Sheet was published by the Clinical Nutrition Service, Warren Grant Magnuson Clinical Center, National Institutes of Health (NIH), Bethesda, MD, in conjunction with the Office of Dietary Supplements (ODS) in the Office of the Director of NIH. The mission of ODS is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an enhanced quality of life and health for the U.S. population. The Clinical Nutrition Service and the ODS would like to thank the expert scientific reviewers for their role in ensuring the scientific accuracy of the information discussed in this Fact Sheet.

http://ods.od.nih.gov/factsheets/vitamind.asp

[Electron Micrograph of a plant cell's endoplasmic reticulum. Copyright Daniel Kunkel]

The endoplasmic reticulum (ER) is responsible for the production of the protein and lipid components of most of the cell's organelles. The ER contains a great amount of folds - but the membrane forms a single sheet enclosing a single closed sac. This internal space is called the ER lumen. The ER is additionally responsible for moving proteins and other carbohydrates to the Golgi apparatus, to the plasma membrane, to the lysosomes, or wherever else needed.

There are two types of ER - rough, which is coated with ribosomes, and smooth, which isn't. Rough ER is the site of protein synthesis. The smooth ER is where the vesicles carrying newly synthesized proteins (from the rough ER) are budded off.

The mitochondrion consists of four major sections – the outer membrane, the intermembrane space, the inner membrane, and the matrix.

The mitochondrion consists of four major sections – the outer membrane, the intermembrane space, the inner membrane, and the matrix.

Left: Diagram of a mitochondrion. Right: Electron Micrograph of a mitochondrion.

The Outer Membrane

This membrane contains a great number of large transport proteins, which allows for large molecules to enter with ease. This membrane includes proteins that can convert lipid substrates into forms that can be used by the matrix.

The Intermembrane Space

This space contains enzymes that use ATP to phosphorylate other nucleotides.

The Inner Membrane

This membrane is highly convoluted, forming many folds called cristae. This serves to greatly increase the surface area, allowing more work to be done is a smaller space. It contains three major proteins - 1. the proteins that carry out the oxidation reactions of the respiratory chain, 2. an enzyme complex called ATP synthetase which makes ATP, and 3. transport proteins which regulate the transfer of molecules into and out of the matrix. This is where the oxidation phosphorylation takes place.

The Matrix

The Kreb Cycle takes place here. It also contains several copies of the mitochondrial DNA genome, special mitochondrial ribosomes, tRNAs, and various enzymes required for the expression of the mitochondrial gene.

Living organisms are complex systems. Hundreds of thousands of proteins exist inside each one of us to help carry out our daily functions. These proteins are produced locally, assembled piece-by-piece to exact specifications. An enormous amount of information is required to manage this complex system correctly. This information, detailing the specific structure of the proteins inside of our bodies, is stored in a set of molecules called nucleic acids.

The nucleic acids are very large molecules that have two main parts. The backbone of a nucleic acid is made of alternating sugar and phosphate molecules bonded together in a long chain, represented below:

Each of the sugar groups in the backbone is attached (via the bond shown in red) to a third type of molecule called a nucleotide base:

Though only four different nucleotide bases can occur in a nucleic acid, each nucleic acid contains millions of bases bonded to it. The order in which these nucleotide bases appear in the nucleic acid is the coding for the information carried in the molecule. In other words, the nucleotide bases serve as a sort of genetic alphabet on which the structure of each protein in our bodies is encoded.

DNA
In most living organisms (except for viruses), genetic information is stored in the molecule deoxyribonucleic acid, or DNA. DNA is made and resides in the nucleus of living cells. DNA gets its name from the sugar molecule contained in its backbone(deoxyribose); however, it gets its significance from its unique structure. Four different nucleotide bases occur in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T).

Chemical Structure of the DNA Nucleotides

These nucleotides bind to the sugar backbone of the molecule as follows:

A		T		G		C
sugar	phosphate	sugar	phosphate	sugar	phosphate	sugar	...

The versatility of DNA comes from the fact that the molecule is actually double-stranded. The nucleotide bases of the DNA molecule form complementary pairs: The nucleotides hydrogen bond to another nucleotide base in a strand of DNA opposite to the original. This bonding is specific, and adenine always bonds to thymine (and vice versa) and guanine always bonds to cytosine (and vice versa). This bonding occurs across the molecule, leading to a double-stranded system as pictured below:

In the early 1950s, four scientists, James Watson and Francis Crick at Cambridge University and Maurice Wilkins and Rosalind Franklin at King's College, determined the true structure of DNA from data and X-ray pictures of the molecule that Franklin had taken. In 1953, Watson and Crick published a paper in the scientific journal Nature describing this research. Watson, Crick, Wilkins and Franklin had shown that not only is the DNA molecule double-stranded, but the two strands wrap around each other forming a coil, or helix. The true structure of the DNA molecule is a double helix, as shown at right.

The double-stranded DNA molecule has the unique ability that it can make exact copies of itself, or self-replicate. When more DNA is required by an organism (such as during reproduction or cell growth) the hydrogen bonds between the nucleotide bases break and the two single strands of DNA separate. New complementary bases are brought in by the cell and paired up with each of the two separate strands, thus forming two new, identical, double-stranded DNA molecules. This concept is illustrated in the animation below.

The Replication of DNA

Concept simulation - Reenacts replication of DNA.

(Flash required)

RNA

Ribonucleic acid, or RNA, gets its name from the sugar group in the molecule's backbone - ribose. Several important similarities and differences exist between RNA and DNA. Like DNA, RNA has a sugar-phosphate backbone with nucleotide bases attached to it. Like DNA, RNA contains the bases adenine (A), cytosine (C), and guanine (G); however, RNA does not contain thymine, instead, RNA's fourth nucleotide is the base uracil (U). Unlike the double-stranded DNA molecule, RNA is a single-stranded molecule. RNA is the main genetic material used in the organisms called viruses, and RNA is also important in the production of proteins in other living organisms. RNA can move around the cells of living organisms and thus serves as a sort of genetic messenger, relaying the information stored in the cell's DNA out from the nucleus to other parts of the cell where it is used to help make proteins.

A		U		G		C
sugar	phosphate	sugar	phosphate	sugar	phosphate	sugar	...
RNA

The skin prick test is a common method of determining whether a person is sensitive to various allergens. It can also determine the person's degree of sensitivity to the allergens. The skin prick test is economical and the results are immediate. The concept is to introduce small quantities of different allergens to the patient's skin (usually back or arm), to see which allergens cause swelling. Swelling, and the degree of swelling, indicates an allergy to the substance, and gives an indication of the degree of sensitivity to the substance. Several days before the test, the patient must not take any antihistamines (common in medicine for flu or colds), as these will bias the results.To administer the allergen, a specialized plastic instrument like the GreerPik is dipped into a valve containing the allergen extract solution, and this instrument is then used to lightly scratch the skin. The allergen will thus penetrate into the skin. There is no bleeding or scarring. Once used, the device is discarded. Many allergens can be tested at the same time, with each test area being 3 cm to 5 cm apart, otherwise overlapping might lead to possible misinterpretations. Each test area on the skin may be marked with ink to prevent confusion among the different allergens. To be on the safe side, positive and negative controls will also be performed by testing with a glycerinated histamine control and a glycerinated placebo control respectively. These added steps will reduce chances of false-negatives (no reaction to allergens where an allergy is actually present) and false-positives (positive reaction to allergens but no allergy is actually present). A false-negative may indicate that the patient could be on antihistamines, which had suppressed his body's reaction to the allergens. Within 15 to 20 minutes, the doctor or nurse is able to determine the patient's allergies. Assessment of both the wheal (swelling and edema) and erythema (flame/redness) reactions are conducted and recorded. Whilst there are various methods in use for grading of skin test reactions to allergens, a common method estimates the degree of sensitivity on a scale of 1 to 4, depending on the size of the reaction. It is important to note however, that individual patients may react differently with time, antigen potency, drug use, immunotherapy as well as testing technique.

Besides taking measures against common allergens like dust mite allergens, one should also check for food allergies. According to the Food Allergy Network, eight foods cause go% of all food allergic reactions. These are: cow's milk, egg, wheat, peanut, soy, nuts, fish and shellfish. Besides these, there are many other foods that have been reported to give allergic reactions to people. Allergic symptoms can begin within minutes, or hours after taking the food. Milk is the most common cause of food allergies in children. Other common causes are eggs, wheat, peanut, soy and tree nuts. What are hidden foods? Another problematic food is soy. Because soy is found in most Asian cooking (in the form of soya sauce, bean curd or other derivatives), it is very difficult to avoid. In Japan,where soy is used more liberally in meals, there is a higher prevalence of soy allergy than in the West. It is also called a "hidden food", since it is often hidden in foods that are not suspect. For example, soy is also found in soy lechitin, which is commonly used in chocolates.What about food additives? Besides natural foods, additives and preservatives are a cause of allergic reactions. A common allergenic preservative are sulphites, found in some foods and medicine. They are used in restaurant foods, wine, beer, fruit drinks, dried fruit, as well as baked and processed food. They can cause serious asthma attacks in sensitive individuals. Other allergenic additives include colouring dyes used in foods and drinks. Examples are tartrazine (E102), sunset yellow (Eilo) and benzoates (E211). These are used in many convenience foods, orange drinks, soft drinks, beer, and margarine. Common reactions to food allergies include vomiting, diarrhoea, skin rashes, asthma, rhinitis, itching tongue and lips, larynx swelling, and a choking sensation.

Moulds are microscopic fungi. They grow in clusters of filaments. Unlike plants, moulds are unable to produce their own food from sunlight and air. They get their nourishment by decomposing or breaking down dead plants and animals.There are tens of thousands of different varieties of moulds. Some moulds produce potent toxins. Others are major sources of plant diseases. Many moulds reproduce by releasing spores into the air, which then settle on organic matter and grow into new mould clusters. There are far more numerous airborne mould spores than there are pollen grains. Where are moulds found? Moulds are found almost anywhere - both indoors and outdoors. Warm and humid conditions encourage mould growth. Thus hot, humid tropical environments are perfect for mould growth. Outdoors, they grow best in shady, damp areas, and on decaying leaves and other vegetation. Moulds produced outdoors can become widely dispersed through the air, and can enter the home. Indoors, mould usually grow in areas like bathrooms and basements. Mould can also occur within the centralised air-conditioning of commercial offices. This could be a source of sick building syndrome or building related illnesses, including allergic reactions.

Pets are a source of companionship, security and happiness. Children often learn lessons on responsibility, life, and death, through their relationships with their pets. While there are few statistics from Asia, in the US, the Academy of Asthma, Allergy and Immunology (ACAAI) estimates that io percent of the population may be allergic to animals. And 20 to 30 percent of individuals with asthma have pet allergies. For those allergic to existing pets, the most effective approach is to find a new family to adopt the pet. However, in the case of cats, the allergen has been known to remain in the house long after the cat is gone. People can have allergic reactions because the previous home owner had a cat in the house. Also, parting with a loved pet is a traumatic experience that many are not willing to go through. Fortunately, there are concrete steps that a household can take to help manage pet allergies, while keeping the pet. A common misconception is the, it is the fur or feathers that cause the reaction. Rather, it is the protein found in the saliva, dander (dead skin flakes) or urine of an animal. These tiny proteins can easily go airborne and can be easily inhaled. Some people react within minutes of exposure, whereas others may take eight to twelve hours to develop symptoms. Cat allergy usually refers to the dried saliva on their fur (which gets there when they lick themselves). Their saliva is more potent than their dander or urine, and can easily go airborne when dried. Dog allergy is mainly caused by their dander which is constantly being shed into the environment. Birds usually shed dander in the form of feather dust, and they become airborne when the birds flutter about.
Allergies to small furry pets like hamsters, guinea pigs, mice and rabbits are caused by their urine. In addition to allergic reactions to animals themselves, droppings from caged pets (like birds, hamsters and mice) can be a source of bacteria, dust, fungi and mould. And dogs running in the park have been known to bring pollen and weed allergens back to the owners. A highly sensitive individual can consider keeping fish, turtles, frogs or tortoises as pets. These pets do not shed dander or have hair or fur, and their droppings do not create allergic problems.
If you are contemplating on getting a pet, it is a good idea to spend time with a friend's dog or cat to see whether you react to them.

Moulds are microscopic fungi. They grow in clusters of filaments. Unlike plants, moulds are unable to produce their own food from sunlight and air. They get their nourishment by decomposing or breaking down dead plants and animals. There are tens of thousands of different varieties of moulds.Some moulds produce potent toxins. Others are major sources of plant diseases. Many moulds reproduce by releasing spores into the air, which then settle on organic matter and grow into new mould clusters. There are far more numerous airborne mould spores than there are pollen grains.

Moulds are found almost anywhere - both indoors and outdoors. Warm and humid conditions encourage mould growth. Thus hot, humid tropical environments are perfect for mould growth. Outdoors, they grow best in shady, damp areas, and on decaying leaves and other vegetation. Moulds produced outdoors can become widely dispersed through the air, and can enter the home. Indoors, mould usually grow in areas like bathrooms and basements. Mould can also occur within the centralised air-conditioning of commercial offices. This could be a source of sick building syndrome or building related illnesses, including allergic reactions.

House dust is a mixture of various waste materials like dead human skin cells, animal dander, fabric fibres, dust mites, bacteria, cockroach parts, mould spres, food particles and other debris. Of these, dead skill cells account for 80% of house dust. However, it is the house dust mite allergen that is the most common contributor to allergic asthma, allergic rhinitis and atopic eczema.

So generally, when doctors say that patients are allergic to house dust, they usually refer to the house dust mite. Of course, patients could also be allergic to other elements of house dust, such as cockrach parts, mould, animal dander and so on.

Dust mite are eight-legged insects that below to the spider and tick famiy or simply known as Arachnid family. They are usually invisible without a microscope.They belong to genus Dermatophagoides which means "skin eater". It is so named because it feed on animal materials with high protein content especially dead human skill cells. It also feeds on mould.

The two most common species thoughout the world that are also allergenic are Dermatiphagoides Peteronyssinus, and Dermatiphagoides farinae. However in the tropics, like Singapore, the Blomia Tropicalis is also a major offender. The female dust mite lays up to 50 eggs within 3 weeks and each egg takes about 3 to 4 weeks to reach adulthood. The lifespan of a dust mite is about 10 weeks, and each female would laid between 40 to 80 eggs within a period of about 6 weeks. So, it is easy to see that they multiply at a fast rate indeed , especially in the right conditions such as hot, humid environment.

The common misconception is that the dust mite itself is the allergen that causes the allergic reaction. Actually, it is the faecal dropping of the dust mites as well as their decaying carcasses which contain the offending allergen - an enzyme that is used to digest their food.

A dustr mite can produce 20 faecal dropping per day, or 200 times their body weight in their short lifetime. Some estimate that 10% of a 2 year old pillow's weight can be made up of dust mites and their dropping.

A gram of dust can contain as many as 1000 dust mites. This same gram can contain 250000 faecal pellets that are much smaller and lighter than dust mites and whcih can easily be inhaled into the lungs.

When using ionizing radiation such as Gamma ray, one should make sure that he stay away from this harmful radiation. The radiation might be too dangerous if there is no one layer of medium to product us. Gamma ray is exist in nuclear power plant and hospital, especially people working in nuclear power plant should wear a strip to determine how much radiation he has taken in a day. The following image show the result of exposing to ionizing radiation. It causes cancer in human. Ionizing radiation damage human blueprint which is the DNA and cause cell to function wrongly such as grow rapidly, this is known as cancerous cell.

Look at this spider, it has hairy legs and seem to be a ready predator.
Spiders occur in a large range of sizes.Small spider is less than 1 mm in body length. The largest and heaviest spiders occur among , which can have body lengths up to 90 mm and leg spans up to 250 mm.

Spiders can live between 1 to 2 years but some spider can live up to 10 or 20 years.

Spiders reproduce by eggs.

Digestion is carried out internally and externally. Spiders that do not have powerful chelicerae, secrete digestive fluids into their prey from a series of ducts perforating their chelicerae. These digestive fluids dissolve the prey's internal tissues. Then the spider feeds by sucking the partially digested fluids out. Other spiders with more powerfully built chelicerae masticate the entire body of their prey and leave behind only a relatively small residue of indigestible materials. Spiders consume only liquid foods. Many spiders will store prey temporarily. Web weaving spiders that have made a shroud of silk to quiet their envenomed prey's death struggles will generally leave them in these shrouds and then consume them at their leisure. Spiders are capable of digesting their own silk, so some spiders may eat their used webs. When a spider drops down on a single strand of silk and then returns, it will generally rapidly consume the strand of silk on its way back up.

Biological safety cabinets are primary devices intended to contain and minimize exposure when working with biological dangerous materials. They are often, but incorrectly describe as laminar flow cabinet, tissue culture hoods, and biological fume hoods. Biological safety cabinets are designed to protect laboratory personnel against exposure during experimental procedures (personnel protection), as well as protect experimental materials from contamination (product protection). They are recommended for manipulations of infectious agents that are likely to create aerosols (i.e., aspirating with a syringe, removing caps from tubes after centrifugation, vortexing of open tubes, sonication, etc.). Additionally, they are also used when manipulating human blood and body fluids, generating high concentrations or large volumes of infectious agents, and when working with and maintaining sterile cell and tissue cultures.

Biological safety cabinets utilize vertical laminar airflow (i.e., uniform air velocity in one direction along parallel flow lines) to achieve a barrier of protection against airborne contaminants, such as microorganisms. The laminar airflow reduces turbulence in the work area, and minimizes the potential for cross-contamination. HEPA (High Efficiency Particulate Air) filters, creating a nearly sterile work environment remove airborne particles going into the work area and out to the environment. The filters have an efficiency of 99.97% with particles that are 0.3um, and higher efficiencies (99.99%) with particles above and below that size. HEPA filters are made of borosilicate fibers, pleated to increase the overall surface area, divided by separators, and glued into a frame. Careless handling of the filters or cabinet (during movement) can damage the filter medium at a joint or cause a tear that will compromise the filter integrity and render the BSC unusable.

Biological safety cabinets must be routinely inspected for proper airflow and filter integrity to ensure that they are providing protection to the worker and the environment. Certification must be performed when a new BSC is first installed (damage or misadjustments can occur during shipment) and annually thereafter by a qualified technician according to the National Sanitation Foundation Standard No. 49, "Class II (Laminar Flow) Biohazard Cabinetry." Your BSC should have a label indicating the date it was last tested. In addition, BSCs must be inspected and certified when they are moved to a new location, or when the HEPA filters are changed. Please call EH&S (5-8200) to obtain the names and telephone numbers of licensed contractors.

The proper use of biological safety cabinets (BSC) can complement good microbiological practices and result in effective containment and control of biohazardous and infectious agents. General guidelines include:

Locating the BSC "deep" in the laboratory away from air currents produced by ventilation inlets, opening/closing of the laboratory door(s), and away from areas of heavy traffic. If possible, close laboratory doors and limit entry, egress and walking traffic. Air currents and movements create turbulence that disrupt the protective envelope of the cabinet. Additionally, other nearby laboratory equipment such as centrifuges, vacuum pumps, etc. can affect the performance of the BSC. Cabinets should not be located directly opposite of each other or opposite a chemical fume hood, as laminar airflow will be hindered.

Observing the magnehelic gauge and noting its relative position each time that the BSC is operated. The magnehelic gauge measures the pressure drop across the HEPA filters and thus indicates filter load and integrity. A significant increase or decrease in the pressure over a short period of time may indicate clogging or leaking of the filter.

Planning and preparing for your work in the cabinet by having a checklist of materials needed and placing those materials in the BSC before commencing work. This reduces the number of arm movements across the air barrier of the cabinet, thereby preserving the protective envelope and containment properties. Slow movement of arms in and out of the cabinet will reduce the risk of potential contamination.

Operational Procedures:

* Ready the work area. Operate cabinet blowers for five min before beginning work to allow the cabinet to purge or remove particulates from the cabinet.
* Disinfect the work area. Wipe the work surface, interior walls and surface of the window with a suitable disinfectant such as 70% ethanol, an iodophor, or quaternary ammonium compound.
* Assemble material. Introduce only those items that are required to perform the procedures and arrange in a logical order. Each item should be wiped with disinfectant prior to placing it into the cabinet to reduce the introduction of contaminants, such as mold spores. The flow of work should proceed across the work surface from clean to contaminated areas. Similarly, pipette discard trays containing disinfectant, biohazard bags, sharps containers, etc. should be placed to one side inside the BSC. This limited motion in and out of the cabinet preserves the protective envelope, and prevents the release of infectious materials outside of the BSC.
* Don protective clothing. Laboratory coats or solid front gowns should be worn over street clothing and long-cuffed latex or other appropriate (e.g., nitrile, vinyl) gloves should be worn for hand protection. The cuffs of the gloves should be pulled up and over the cuffs of the coat sleeves.
* Perform procedures. Slowly move arms when working and when moving items in and out of the cabinet. Avoid rapid movements during procedures. After placing arms/hands inside the BSC manipulations should be delayed to permit the cabinet to stabilize and allow the flow of air to remove surface contaminants from your arms/hands.
* Do not block the front grille with papers, equipment, etc. as this may cause air to enter the work space area instead of being drawn through the front grille and to the HEPA filter. Arms should be raised slightly, and operations should be performed on the work surface at least 4 in from the front grille. The middle third area is ideal. Likewise, no operations or equipment should block the rear exhaust grille. Any equipment generating aerosols, such as a microcentrifuge, vortex or blender, should be placed near the rear of the cabinet. A disinfectant-soaked towel can be placed on the work surface to contain any spills or splatters that may occur.
* Open flames inside the cabinet create turbulence that can disrupt the pattern of air and compromise the safety of the operator and affect product protection (i.e., cause contamination). Flames can also damage the interior of the cabinet as well as the HEPA filters. If a burner is necessary to sterilize tools such as a loop or needle, consider the use of a touch plate burner that provides a flame on demand, and place it to the rear of the cabinet. Alternatively, electric furnaces or disposable, sterile tools can be used.
* If culture media or other fluids need to be aspirated, suction or aspirator flasks should be connected to an overflow collection flask containing disinfectant (the aspirated materials can then be discarded as noninfectious waste). The flasks should then be coupled to an inline HEPA or equivalent filter designed to protect the vacuum system.
* When work is completed all items within the cabinet should be wiped down with disinfectant and removed from the cabinet. Do not use the interior of the BSC as a storage area since stray organisms may become "trapped" and contaminate future experiments. The interior surfaces of the cabinet should also be cleaned with a suitable disinfectant. Let the blowers operate for five minutes, with no activity inside the cabinet, to purge the cabinet of contaminants.
* Investigators should remove their gowns and gloves and thoroughly wash their hands before exiting the laboratory.

Use of ultraviolet lights in the biosafety cabinet:

Ultraviolet lights are a common accessory of many BSCs. These lamps are regarded as biocidal devices, "protecting" the operator from exposure to infectious agents and experimental materials from contamination. However, the actual effectiveness of UV light in providing this "sterile" environment has been questioned. Additionally, there are potential occupational hazards that carry significant risks (e.g., serious eye and skin injury) associated with the use and misuse of these lamps. Ultraviolet lamps must be periodically tested to ensure that the energy output is adequate to kill microorganisms. The radiation output should be at least 40microwatts/ cm2 at 254 nm when measured with a UV flux meter placed in the center of the work surface. The output performance of the lamps is adversely affected by dust accumulating on the surface of the lamps (UV light is unable to penetrate through dust or other materials), and microorganisms adhering to floating dust particles or other fixed objects are also protected and unaffected by UV illumination. Ultraviolet exposure damaging to the eyes and skin exists well after the output of the lamps has dropped below the biocidal level. The effective life spans of the lamps are relatively short and the bulbs are expensive to replace. As a result, Environmental Health & Safety dissuades operators from using UV lights to maintain a clean working environment. A significantly more effective and recommended strategy to reduce or eliminate contamination utilizes well-practiced microbiological procedures, good aseptic techniques, operational procedures outlined in this document, and thorough decontamination procedures before and after BSC use.

Types of Biological Safety Cabinets:

Three general classes of cabinets are defined; class I, open-front air inflow cabinet; class II, several subtypes of open-front vertical airflow cabinets (very common); and class III, totally enclosed, gas-tight ventilated cabinets with work operations conducted through fixed, attached rubber gloves. Class I and II cabinets (used exclusively on campus) are described below.

Class I: Good protection for the operator, but no product protection, is provided with these cabinets. Air flow, at a minimum inward face velocity of 75 linear feet per minute (lfpm), is directed through the front opening, across the work area and out through the HEPA filter on top. This cabinet is conventionally used with a full width open front, or can be used with an attached armhole front panel with or without attached rubber gloves. Although class I cabinets are simple and economical, and radioisotopes and some toxic chemicals can be used (if exhaust is ducted to the outside), filtered air is not provided over the work area. These cabinets do not protect your materials from contaminants introduced from the environment or the operator.

Class II: Unlike class I cabinets, class II cabinets afford protection for the operator AND the work performed. The capacity to protect materials within the cabinet is provided by the flow of HEPA-filtered air over the work surface. There are four subtypes of Class II cabinets based on the construction, inflow air velocities, and the exhaust systems. These cabinets can be used to manipulate low to moderate risk agents.

Class IIA: Air, at a face velocity of 75 lfpm, is drawn into the front grille of the cabinet away from the work surface. The air is directed through a HEPA filter and downward over the work area. As the air approaches the work surface, the blower draws part of the air through the front grille and the remainder through the rear grille. Approximately 70% of the air is recirculated to the work zone through the supply HEPA filter, and about 30% is exhausted to the room through another HEPA filter. This cabinet is unsuitable for work that involves radioactive materials and toxic chemicals because of the buildup of vapors in the air recirculated within the cabinet and out into the laboratory.

Class IIB1: As with the class IIA cabinet inflow air (face velocity of 100 lfpm) is ultimately forced through a HEPA filter and over the work area, where there is a split of downward flowing air. About 70% of the air is directed through a HEPA filter to the outside (must be hard-ducted, preferably with its own exhaust system), whereas 30% is drawn through the front grille and recirculated. Minute amounts of toxic chemicals and trace amounts of radioisotopes can be used within the hood, although activities should be conducted toward the rear of the cabinet.

Class IIB2: This cabinet is a total exhaust cabinet; no air is circulated within it. A supply blower draws in room air or outside air at the top of cabinet, through a HEPA filter and down into the work area. Additional room air is drawn through the front grilles at a face velocity of 100 lfpm. The air discharged from this cabinet must be 100% exhausted outside through a HEPA filter in a dedicated hard duct. Small quantities of toxic chemicals and radioisotopes can be used within the hood. The exhaust of a large volume of conditioned room air makes this cabinet very expensive to operate. Additionally, the cabinet must be running continuously so as not to interfere with room exhaust. Should building or cabinet exhaust fail, the blower motors should be turned off to prevent a back flow of pressurized air from the cabinet work area into the laboratory.

Class IIB3: This is a combination A/B cabinet with a face velocity of 100 lfpm. This cabinet can be used as a class A cabinet where exhaust air is recirculated in the laboratory. Alternatively, it can be used as a class IIB cabinet and exhaust air vented to the outside with a thimble unit connected to the duct. Biologically contaminated ducts and plenums are under negative pressure to the room and exhaust air. Approximately 70% of the air is exhausted, whereas 30% is recirculated within the cabinet. Minute quantities of toxic chemicals and trace amounts of radioisotopes can be used.

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The biological safety cabinet (BSC) is designed to provide protection to personnel and the environment when appropriate practices and procedures are followed. Three types of BSCs (Class I, II, III) are described below. Class II biological safety cabinets are most often used with moderate risk organisms.

The common element to all classes of biological safety cabinets is the high efficiency particulate air (HEPA) filter. This filter removes particles of 0.3 microns (which essentially includes all bacteria, spores, and viruses) with an efficiency of 99.97%. However, it does not remove vapors or gases.

The biosafety cabinet requires regular maintenance and certification by a professional technician to assure that it protects you, your experiments, and the environment. Each cabinet should be certified when it is installed, each time it is moved or repaired, and at least annually. The Department of Environmental Safety administers a program for annual certification of all biological safety cabinets at the university with no cost to the user. Contact DES at (301) 405-3975 to confirm that your cabinet is included in this program.

1. Class I cabinets protect personnel and the environment, but not research materials. They provide an inward flow of unfiltered air, similar to a chemical fume hood, which protects the worker from the material in the cabinet. The environment is protected by HEPA filtration of the exhaust air before it is discharged into the laboratory or to the outside via the building exhaust.
2. Class II (Types A, B1, B2, and B3) biological safety cabinets provide personnel, environment, and product protection. Air is drawn around the operator into the front grille of the cabinet, which provides personnel protection. In addition, the downward laminar flow of HEPA-filtered air provides product protection by minimizing the chance of cross-contamination along the work surface of the cabinet. Because cabinet air has passed through the exhaust HEPA filter, it is contaminant-free (environment protection), and may be recirculated back into the laboratory (Type A) or ducted out of the building (Type B).
3. Class III cabinets (sometimes called Class III glove boxes) were designed for work with infectious agents that require Biosafety Level 4 containment, and provide maximum protection to the environment and the worker. The cabinet is gas-tight with a non-opening view window, and has rubber gloves attached to ports in the cabinet that allow for manipulation of materials in the cabinet. Air is filtered through one HEPA filter as it enters the cabinet, and through 2 HEPA filters before it is exhausted to the outdoors. This type of cabinet provides the highest level of product, environmental, and personnel protection.
4. Horizontal laminar flow "clean air benches" are not BSCs. They discharge HEPA-filtered air across the work surface and toward the user, providing only product protection. They can be used for certain clean activities, such as dust-free assembly of sterile equipment or electronic devices. However, they should never be used when handling cell culture materials or potentially infectious materials, or as a substitute for a biological safety cabinet in research laboratories.

Bioburden or Microbial limit testing is performed on pharmaceutical products and medical products as a quality control measure. Products or components used in the pharmaceutical or medical field require control of microbial levels during processing and handling. Bioburden or microbial limit testing on these products prove that the requirements are met.

Bioburden of raw material as well as finished pharmaceutical products can help to determine whether the product complies with the requirements of the BP, Ph. Eur. or USP. Bioburden testing of components can show the use of adequate control measures during the preparation and handling.

Bioburden, according to the University of Rochester glossary, is the number of microorganisms with which an object is contaminated. This unit is measured in CFU (colony forming units) per gram of product. In industry the number of measured CFU should not exceed an un-processed bulk action limit. These limits are required by the FDA and similar regulatory bodies to ensure the acceptablility of a drug product. The drug is also required to be tested as a bulk drug substance (bds).

I went for a prick skin test to see if I am allergy to any commonly items just now and the process took 20 minutes. The nurse add 8 drops of different active agent on my hand each. What I could remember was she added Histamine, 3 type of Dust Mine enzyme, bermuda grass, dog hair, cat hair, cockroaches mix, 7 grass mix as if gonna cook a witch meal a million taste.

In the 20 minutes, I cannot move my hand and was forced to read the book which is about allergy. When finish one page, the nurse turn to another page for me. Then finish reading, I wanted to say: "nurse ar, next page" but i see that she is so busy so I hardly turn myself, lucky never pour any droplet.

In the very first 5 minutes, 4 areas become swollen. 3 on the left side and 1 on the right hand. After the test, I got dust mite allergy and histamine allergy.

For what I know, dust mite is classified as spider because it has 8 legs. It is found anyway and nobody can get away from it. Even the chair we sit and the bed we lie and all other sort of soft items we use all contain Dust Mite. The image of Dust Mite is shown below, it is just more or less that it stay in our hair and body. It can only be visible through a microscope. I am allergy to the waste of this microorganism. Yuck, have 8 legs!!!

The nurse told me that 70% of Singaporean is allergy to dust mite and whoever belong to the 30% is so lucky. Those who get this allergy will pass down their mutated gene to their next generation and propargate throughout until a proper virus is developed to add the correct gene so that we can resist Dust Mine Enzyme.

Ultraviolet (UV) "light" is a type of electromagnetic radiation. UV light has a shorter wavelength than visible light. Purple and violet light have shorter wavelengths than other colors of light, and ultraviolet has even shorter waves than violet does; so ultraviolet is sort of "purpler-than-purple" light or "beyond violet" light.

Ultraviolet radiation lies between visible light and X-rays on the electromagnetic spectrum. UV "light" has wavelengths between about 380 and 10 nanometers. The wavelength of violet light is around 400 nanometers (or 4,000 Å). Ultraviolet radiation oscillates at rates between about 800 terahertz (THz or 1012 hertz) and 30,000 THz.

The ultraviolet spectrum is sometimes subdivided into the near UV (380 to 200 nanometer wavelengths) and extreme UV (200 to 10 nm wavelengths). Normal air is largely opaque to UV with wavelengths shorter than 200 nm (the extreme UV range); oxygen absorbs "light" in that part of the UV spectrum.

In terms of impact on the environment and human health (and choosing sunglasses!), it can be useful to subdivide the UV spectrum in a different way, into UV-A ("blacklight" or Long Wave UV with a 380 to 315 nm wavelength), UV-B (Medium Wave at 315 to 280 nm), and UV-C (the "germicidal" or Short Wave UV that ranges from 280 to 10 nm).

Earth's atmosphere prevents most UV radiation from space from reaching the ground. UV-C is entirely screened out by stratospheric ozone at around 35 km altitude. Most UV-A does reach the surface, but UV-A does little genetic damage to tissues. UV-B is largely responsible for sunburn and skin cancer, though it is mostly absorbed by ozone before reaching the surface. Levels of UV-B radiation at the surface are especially sensitive to levels of ozone in the stratosphere.

Ultraviolet radiation causes sunburn. It is used to sterilize glassware used in medicine and biological research.

What is HIV?

HIV (human immunodeficiency virus) is the virus that causes AIDS (acquired immunodeficiency syndrome). By killing or damaging cells of your body's immune system, HIV progressively destroys your body's ability to fight infections and certain cancers. People diagnosed with AIDS may get life-threatening diseases called opportunistic infections, which are caused by microbes such as viruses or bacteria that usually do not make healthy people sick.

More than 700,000 cases of AIDS have been reported in the United States since 1981, and as many as 900,000 Americans may be infected with HIV. There are as many as 275,000 who may not know they are infected and can pass the virus on.
How Does HIV Affect the Body?
A healthy body is equipped with CD4 helper lymphocyte cells (CD4 cells). These cells help the immune system function normally and fight off certain kinds of infections. They do this by acting as messengers to other types of immune system cells, telling them to become active and fight against an invading germ.

HIV attaches to these CD4 cells, infects them, and uses them as a place to multiply. In doing so, the virus destroys the ability of the infected cells to do their job in the immune system. The body then loses the ability to fight many infections.

Because their immune systems are weakened, people who have AIDS are unable to fight off many infections, particularly tuberculosis and other kinds of otherwise rare infections of the lung (such as Pneumocystis carinii pneumonia), the surface covering of the brain (meningitis), or the brain itself (encephalitis). People who have AIDS tend to keep getting sicker, especially if they are not taking antiviral medications properly.

AIDS can affect every body system. The immune defect caused by having too few CD4 cells also permits some cancers that are stimulated by viral illness to occur — some people with AIDS get forms of lymphoma and a rare tumor of blood vessels in the skin called Kaposi's sarcoma. Because AIDS is fatal, it's important that doctors detect HIV infection as early as possible so a person can take medication to delay the onset of AIDS.

How Do People Know They Have HIV?
Once a person's blood lacks the number of CD4 cells required to fight infections, or the person has signs of specific illnesses or diseases that occur in people with HIV infection, doctors make a diagnosis of AIDS.

Severe symptoms of HIV infection and AIDS may not appear for 10 years. And for years leading up to that, a person may not have symptoms of AIDS. The amount of time it takes for symptoms of AIDS to appear varies from person to person. Some people may feel and look healthy for years while they are infected with HIV. It is still possible to infect others with HIV, even if the person with the virus has absolutely no symptoms. You cannot tell simply by looking at someone whether he or she is infected.

When a person's immune system is overwhelmed by AIDS, the symptoms can include:

extreme weakness or fatigue
rapid weight loss
frequent fevers that last for several weeks with no explanation
heavy sweating at night
swollen lymph glands
minor infections that cause skin rashes and mouth, genital, and anal sores
white spots in the mouth or throat
chronic diarrhea
a cough that won't go away
trouble remembering things
Girls may also experience severe vaginal yeast infections that don't respond to usual treatment, as well as pelvic inflammatory disease (PID).

How Can It Be Prevented?
One of the reasons that HIV is so dangerous is that a person can have the virus for a long time without knowing it. That person can then spread the virus to others through high-risk behaviors. HIV transmission can be prevented by:

abstaining from sex (not having oral, vaginal, or anal sex)
always using latex condoms for all types of sexual intercourse
avoiding contact with the bodily fluids through which HIV is transmitted
never sharing needles
How Is It Diagnosed and Treated?
If you think that you may have HIV or AIDS or if you have had a partner who may have HIV or AIDS, see your family doctor, adolescent doctor, or gynecologist. He or she will talk with you and perform tests. The doctor may do a blood test or a swab of the inside of your cheek. Depending on what type of test is done, results may take from a few hours to several days.

People can also get tested for HIV/AIDS at special AIDS clinics around the country. Clinics offer both anonymous (meaning the clinic doesn't know a person's name) and confidential (meaning they know who a person is but keep it private) testing. Most AIDS testing centers will ask you to follow up for counseling to get your results, whether the test is negative or positive. There is no cure for AIDS, which makes prevention so important. Combinations of antiviral drugs and drugs that boost the immune system have allowed many people with HIV to resist infections, stay healthy, and prolong their lives, but these medications are not a cure. Right now there is no vaccine to prevent HIV and AIDS, although researchers are working on developing one.

Vitamin E is a fat-soluble vitamin that exists in eight different forms. Each form has its own biological activity, which is the measure of potency or functional use in the body.

Alpha-tocopherol (α-tocopherol) is the name of the most active form of vitamin E in humans. It is also a powerful biological antioxidant. Vitamin E in supplements is usually sold as alpha-tocopheryl acetate, a form of alpha-tocopherol that protects its ability to function as an antioxidant. The synthetic form is labeled "D, L" while the natural form is labeled "D". The synthetic form is only half as active as the natural form.

Antioxidants such as vitamin E act to protect your cells against the effects of free radicals, which are potentially damaging by-products of energy metabolism. Free radicals can damage cells and may contribute to the development of cardiovascular disease and cancer. Studies are underway to determine whether vitamin E, through its ability to limit production of free radicals, might help prevent or delay the development of those chronic diseases. Vitamin E has also been shown to play a role in immune function, in DNA repair, and other metabolic processes .

Wheat germ oil, nuts and seeds, whole grains, egg yolks, and leafy green vegetables all contain vitamin E. Certain vegetable oils should contain significant amounts of vitamin E. However, many of the vegetable oils sold in supermarkets have had the vitamin E removed in processing. The high amounts found in supplements, often 100 to 800 IU per day, are not obtainable from eating food.


Vitamin E toxicity is very rare and supplements are widely considered to be safe. The National Academy of Sciences has established the daily tolerable upper intake level for adults to be 1,000 mg of vitamin E, which is equivalent to 1,500 IU of natural vitamin E or 1,100 IU of synthetic vitamin E.

In a double-blind study of healthy elderly people, supplementation with 200 IU of vitamin E per day for 15 months had no effect in the incidence of respiratory infections, but increased the severity of those infections that did occur.For elderly individuals, the risks and benefits of taking this vitamin should be assessed with the help of a doctor or nutritionist.

In contrast to trials suggesting vitamin E improves glucose tolerance in people with diabetes, one trial reported that 600 IU per day of vitamin E led to impairment in glucose tolerance in obese people with diabetes.The reason for the discrepancy between reports is not known.

In a double-blind study of people with established heart disease or diabetes, participants who took 400 IU of vitamin E per day for an average of 4.5 years developed heart failure significantly more often than did those taking a placebo. Hospitalizations for heart failure occurred in 5.8% of those in the vitamin E group, compared with 4.2% of those in the placebo group, a 38.1% increase. Considering that some other studies have shown a beneficial effect of vitamin E against heart disease, the results of this study are difficult to interpret. Nevertheless, individuals with heart disease or diabetes should consult their doctor before taking vitamin E.

A review of 19 clinical trials of vitamin E supplementation concluded that long-term use of large amounts of vitamin E (400 IU per day or more) was associated with a small (4%) but statistically significant increase in risk of death. Long-term use of less than 400 IU per day was associated with a small and statistically nonsignificant reduction in death rates. This research has been criticized because many of the studies on which it was based used a combination of nutritional supplements, not just vitamin E. For example, the adverse effects reported in some of the studies may have been due to the use of large amounts of zinc or synthetic beta-carotene, and may have had nothing to do with vitamin E. It is also possible that long-term use of large amounts of pure alpha-tocopherol may lead to a deficiency of gamma-tocopherol, with potential negative consequences. For that reason, some doctors recommend that people who need to take large amounts of vitamin E take at least part of it in the form of mixed tocopherols.

Patients on kidney dialysis who are given injections of iron frequently experience “oxidative stress.” This is because iron is a pro-oxidant, meaning that it interacts with oxygen molecules in ways that may damage tissues. These adverse effects of iron therapy may be counteracted by supplementation with vitamin E.

A diet high in unsaturated fat increases vitamin E requirements. Vitamin E and selenium work together to protect fat-soluble parts of the body.

Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. Unlike most mammals, humans do not have the ability to make their own vitamin C. Therefore, we must obtain vitamin C through our diet.

Vitamin C is required for the synthesis of collagen, an important structural component of blood vessels, tendons, ligaments, and bone. Vitamin C also plays an important role in the synthesis of the neurotransmitter, norepinephrine. Neurotransmitters are critical to brain function and are known to affect mood. In addition, vitamin C is required for the synthesis of carnitine, a small molecule that is essential for the transport of fat to cellular organelles called mitochondria, for conversion to energy (1). Recent research also suggests that vitamin C is involved in the metabolism of cholesterol to bile acids, which may have implications for blood cholesterol levels and the incidence of gallstones (2).

Vitamin C is also a highly effective antioxidant. Even in small amounts vitamin C can protect indispensable molecules in the body, such as proteins, lipids (fats), carbohydrates, and nucleic acids (DNA and RNA) from damage by free radicals and reactive oxygen species that can be generated during normal metabolism as well as through exposure to toxins and pollutants (e.g. smoking). Vitamin C may also be able to regenerate other antioxidants such as vitamin E.


Severe vitamin C deficiency has been known for many centuries as the potentially fatal disease, scurvy. By the late 1700's the British navy was aware that scurvy could be cured by eating oranges or lemons, even though vitamin C would not be isolated until the early 1930's. Symptoms of scurvy include bleeding and bruising easily, hair and tooth loss, joint pain and swelling. Such symptoms appear to be related to the weakening of blood vessels, connective tissue, and bone, which contain collagen. Early symptoms of scurvy such as fatigue may result from diminished levels of carnitine, needed to derive energy from fat, or decreased synthesis of the neurotransmitter norepinephrine. Scurvy is rare in developed countries because it can be prevented by as little as 10 mg of vitamin C daily. However, recent cases have occurred in children and the elderly on very restricted diets.

The recommended dietary allowance (RDA) for vitamin C in nonsmoking adults is 75 mg per day for women and 90 mg per day for men. For smokers, the RDAs are 110 mg per day for women and 125 mg per day for men. Most clinical vitamin C studies have investigated the effects of a broad range of higher vitamin C intakes (100–1,000 mg per day or more), often not looking for (or finding) the “optimal” intake within that range. In terms of heart disease prevention, as little as 100–200 mg of vitamin C appears to be adequate. Although some doctors recommend 500–1,000 mg per day or more, additional research is needed to determine whether these larger amounts are necessary. Some vitamin C experts propose that adequate intake be considered 200 mg per day because of evidence that the cells of the human body do not take up any more vitamin C when larger daily amounts are used.

Some scientists have recommended that healthy people take multi-gram amounts of vitamin C for the prevention of illness. However, little or no research supports this point of view and it remains controversial. Supplementing more results in an excretion level virtually identical to intake, meaning that consuming more vitamin C does not increase the amount that remains in the body. On the basis of extensive analysis of published vitamin C studies, researchers at the Linus Pauling Institute at Oregon State University have called for the RDA to be increased, but only to 120 mg. This same report reveals that “. . . 90–100 mg vitamin C per day is required for optimum reduction of chronic disease risk in nonsmoking men and women.” Thus, the multiple gram amounts of vitamin C taken by many healthy people may be superfluous.
The studies that ascertained approximately 120–200 mg daily of vitamin C is correct for prevention purposes in healthy people have typically not investigated whether people suffering from various diseases can benefit from larger amounts. In the case of the common cold, a review of published trials found that amounts of 2 grams per day in children appear to be more effective than 1 gram per day in adults, suggesting that large intakes of vitamin C may be more effective than smaller amounts, at least for this condition.

The vitamin B complex consists of eight water soluble vitamins. The B vitamins work together to boost metabolism, enhance the immune system and nervous system, keep the skin and muscles healthy, encourage cell growth and division, and other benefits to your body. Brewer's yeast is one of the best sources of the B vitamins.

Vitamin B1, thiamine, serves as a catalyst in carbohydrate metabolism and helps synthesize nerve-regulating substances. It is a colorless compound with chemical formula C12H17N4OS. . Every cell of the body requires vitamin B1 to form the fuel the body runs on—adenosine triphosphate (ATP). Nerve cells require vitamin B1 in order to function normally. Deficiency can cause heart swelling, leg cramps, and muscular weakness. Rich food sources high in thiamine include liver, heart, and kidney meats, eggs, leafy green vegetables, nuts, legumes, berries, wheat germs, and enriched cereals. The Recommended Dietary Allowance (RDA) is 1.5 mg. Some believe thiamine helps protect against alcoholism and that it is good for depression, stress, and anxiety. It is also said to improve mental ability and to help indigestion. A decline in vitamin B1 levels occurs with age, irrespective of medical condition. 1 Deficiency is most commonly found in alcoholics, people with malabsorption conditions, and those eating a very poor diet. It is also common in children with congenital heart disease. 2 People with chronic fatigue syndrome may also be deficient in vitamin B1. 4 Individuals undergoing regular kidney dialysis may develop severe vitamin B1 deficiency, which can result in potentially fatal complications.5 Persons receiving dialysis should discuss the need for vitamin B1 supplementation with their physician.

Vitamin B2, or riboflavin, helps metabolize fats, carbohydrates, and respiratory proteins. activate vitamin B6 and folic acid, and help convert carbohydrates into the fuel the body runs on—adenosine triphosphate (ATP). Under some conditions, vitamin B2 can act as an antioxidant. A deficiency can result in skin lesions and light sensitivity. Riboflavins are abundant in mushrooms, milk, meat, liver, dark green vegetables, and enriched cereals, pasta, and bread. The RDA is 1.3 mg for adults. The vitamin is good for the skin, nails, eyes, mouths, lips, and tongue, and it is believed to help protect against cancer. Vitamin B2 deficiency can occur in alcoholics. Also, a deficiency may be more likely in people with cataracts or sickle cel anemia. In developing countries, vitamin B2 deficiency has been found to be a risk factor for the development of preeclampsia in pregnant women. People with chronic fatigue syndrome may be deficient in vitamin B2.

B3—also known as niacin, vitamin P, or vitamin PP—helps release energy from nutrients. It can reduce cholesterol and prevent and treat arteriosclerosis, among other benefits. Too little B3 can result in pellagra, a disease with symptoms that include sunburn, diarrhea, irritability, swollen tongue, and mental confusion. Too much B3 can result in liver damage. Food sources rich in niacin are chicken, salmon, tuna, liver, nuts, dried peas, enriched cereals, and dried beans. The RDA is 14-18 mg per day for adults.

Vitamin B5, or Pantothenic acid, has a role in the metabolism of fats, carbohydrates, and proteins. It is a water-soluble vitamin involved in the Kreb’s cycle of energy production and is needed to make the neurotransmitter acetylcholine. It is also essential in producing, transporting, and releasing energy from fats. Synthesis of cholesterol (needed to manufacture vitamin D and steroid hormones) depends on pantothenic acid.It is most abundant in eggs, whole grain cereals, legumes, and meat, although it is found in some quantity in nearly every food. The RDA is 10 mg. Deficiency can result in fatigue, allergies, nausea, and abdominal pain. Pantothenic acid deficiencies may occur in people with alcoholism but are generally believed to be rare.

Vitamin B6 is the master vitamin for processing amino acids—the building blocks of all proteins and some hormones. Vitamin B6 helps to make and take apart many amino acids and is also needed to make the hormones, serotonin, melatonin, and dopamine. Deficiency in the vitamin may result in smooth tongue, skin disorders, dizziness, nausea, anemia, convulsions, and kidney stones. Whole grains, bread, liver, green beans, spinach, avocadoes, and bananas are rich food sources that are high in this vitamin. The RDA ranges from 1.3 to 2 mg depending on age and gender. Vitamin B6 deficiencies are thought to be very rare. Vitamin B6 deficiency can cause impaired immunity, skin lesions, and mental confusion. A marginal deficiency sometimes occurs in alcoholics, patients with kidney failure, and women using oral contraceptives. Some doctors believe that most diets do not provide optimal amounts of this vitamin. People with kidney failure have an increased risk of vitamin B6 deficiency. Vitamin B6 has also been reported to be deficient in some people with chronic fatigue syndrome.

Vitmin B7—also known as Biotin or vitamin H, helps form fatty acids and assists in the release of energy from carbohydrates. There have been no cases of deficiency among humans. The RDA is 30 µg.

Folic acid is a B vitamin needed for cell replication and growth. Folic acid helps form building blocks of DNA, the body’s genetic information, and building blocks of RNA, needed for protein synthesis in all cells. Therefore, rapidly growing tissues, such as those of a fetus, and rapidly regenerating cells, like red blood cells and immune cells, have a high need for folic acid. Folic acid deficiency results in a form of anemia that responds quickly to folic acid supplementation.Folic acid enables the body to form hemoglobin. It helps treat anemia and sprue. Good food sources include leafy green vegetables, nuts, whole grains, legumes, and organ meets. However, bear in mind that folic acid is lost when foods are stored at room temperature or cooked. Deficiency is rare, although folic acid is particularly important in pregnancy. Consuming adequate folic acid before and during pregnancy helps prevent neural tube defects in newborns, including spina bifida. The RDA for both men and women is 400 micrograms, but women who are pregnant or planning to become pregnant should consume 600 micrograms a day. When breastfeeding, the recommendation is 500 micrograms.

Vitamin B12 is is a water-soluble vitamin needed for normal nerve cell activity, DNA replication, and production of the mood-affecting substance SAMe (S-adenosyl-L-methionine). Vitamin B12 acts with folic acid and vitamin B6 to control homocysteine levels. An excess of homocysteine is associated with an increased risk of heart disease, stroke, and potentially other diseases such as osteoporosis and Alzheimer’s disease. If the body is unable to absorb sufficient B12, pernicious anemia can result. B12 can only be found in animal sources such as eggs, milk, fish, meat, and liver. Therefore, vegetarians are strongly encouraged to supplement. The RDA for adult males and females is 2.4 µg.

Vitamin A is a fat soluble vitamin and it is very important for bone growth and better night vision. Beta Carotene is found in plants and the molecule break into 2 to form Vitamin A. Beta Carotene is not toxic but Vitamin A in excess dose is toxic but researcher found that Beta Carotene is not suitable for smoker as it will increase the risk of getting Cancer.

Vitamin A can be found in food such as carrots and spinach. Vitamin A help us to view better at night because it is needed to produce the visual pigment that is used in low light condition. Vitamin A is important for red blood cell formation or else the production can be abnormal. Other than these, Vitamin A also affect our body hormone production such as increasing growth hormone.

All fat soluble vitamin such as Vitamin A, D and E are toxic if overdose because they are stored in the liver. Accumulating of these Vitamin in the liver can cause toxic reaction while Vitamin B and C are safer if overdose as they are lost from the body through urine.

A sterilizing filter has a pore size of 0.22 microns or smaller size. However, one problem with filter is that it cannot remove virus because it is too small.

Membrance filters are commonly used as it will not produce fibre which would otherwise enter together with the products. 4 type of mechanism which can effect the particle removal efficiency are Direct inteception, Inertial impaction, Brownian motion and Electrostatic attraction.

Membrance filters used for sterlize liquid filtration where water content are available use hydrophoic filter so that the filter will not get wet. If the filter is wet, it will not pass air until the water wet bubble point of the filter is exceeded which can be more than 50psi.

Gamma ray and electron tube are classified as Ionizing radiation. They have good penetration power and have high sterilization efficiency. Ionzing radiation cause excitations, ionization and where water are present, free radical are formed which can damage cell. Ionizing radiation damage the cell enzyme and DNA causing cell death.

UV ray at the range of 220 to 280nm are used for sterilization with 265nm as the most effective wavelength. UV ray has a weak penetration power and it cannot pass through thin layer of glass, therefore we cannot totally rely on it for perfect sterilization. UV ray damage the cell DNA and cause it to malfunction and the cell will die.

High voltage and low current are used to generate UV ray.

Chemical sterilization is used when equipment are sensitive to heat. We use chemical such as Ethylene Oxide which is a poisonous gas to kill microorganism. It can take about a day to sterilize product using this method, thus it is rarely use in industry as a sterilizer. The molecule of Ethylene Oxide is small and can penetrate into any product easily. Ethylene Oxide cannot be used on some plastics as it can cause damages to the plastic. The operating cost of Ethylene Oxide is high. Ethylene Oxide is highly flammable. We must always make sure that we do not get contact with the gas as it can also kill human, thus when operating this chemical sterilizer, make sure there are no leakage anywhere.

Dry heat is able to damage pyrogen which could otherwise stay on the suface of the glass container. Dry heat has a disadvantage over moist heat in which it has a bad heat distribution. Therefore a fan is needed to circulate the air inside the oven to prevent stagnant of cold air.

Normally we sterilize product at 160 Degree Celsius for 2 hours, 170 Degree Celsius for 1 hour or 180 Degree Celsius for 30 minutes. It is faster to sterlize at a higher temperature but it is not recommended for some products as high heat can damage the quaity of the product.

Autoclaving is liked a pressure cooker. Water boil at 100 Degree Celsius at atmospheric pressure but with a pressure that increase to 2 bar, the temperature of water can reach to 121.1 Degree Celsisus, the normal temperature for most sterilization process.

Autoclaving provide 7 time as much energy than dry heat at the same temperature. However dry heat is able to remove pyrogen.

Autoclaving are not suitable for dry products or products that will corrode in water. It take a shorter time to autoclave a substance or product when the temperature is higher.

Sanitization is the reduction of microorganism but not completely killing all the cells. Wearing our hand with soap is an example of sanitization.

Disinfection is different from sanitization and people often thought that they are the same. Disinfection is the reduction of pyrogenic cells so that it does not infect other people.

Sterilization is the complete destruction or removal of all cells. Destruction such as autoclaving and dry heat. Removal such as filtration.

Pyrogens are produce by pyrogenic bacteria. They cause fever even in a small amount. In a large amount, pyrogens can cause death from sudden shocked such as high fever and hypotension.

Endotoxins are produced by the outer membrance of the gram negative bacteria or from cell lyse.

Exotoxins are produce by gram postive and gram negative bacteria whereby bacteria manufacture exotoxins from it cell.

Enzyme decrease the activation energy so that reaction that will take a few thousands years to complete will take a second instead. Enzyme are different from catalyst in many ways. Enzyme are macromolecules but catalyst can be as simple as an element. Enzyme are always found in living things to make sure our food are digest properly and burn to energy.

Enzyme are very sensitive to heat, if we increase the heat a little higher, the rate of reaction will increase but if we increase the temperature a lot higher, than there will be a risk that the enzyme will get damage permanently from heat.

pH also effect the usefulness of enzyme. Enzyme react the fastest at optimize pH value so we have to find out what pH is the best for this enzyme through some experiment.

Some enzyme simply don't work without a cofactor. A cofactor is an essential parts of active enzyme which must be present in sufficient concentration to activate enzyme molecules. .

Genes carry information to build proteins and enzymes. 1 gene only carry information to make 1 protein. Human genes are estimated to be more than 30000 and only 10% of the genes are known.

Humans have 46 chromosomes, 22 pairs of non-sex chromosomes while the other chromosome tell us if the child is a boy or girl. If one chromosome is X and the other is Y, the person is a guy. If both are X then the person will be girl.

In our chromosomes, some of the genes are bad gene, they are DNA errors brought down by the old generation; mutation. Depending on the bad genes, some genes produce blood that are unhealthy while some cause diseases such as G6PD.

Genes are the blueprint that allow life to continue and even a change in a small portion of the genes can cause a huge changes in our look.

Application of Proteins
1) Immune system
2) Growth
3) Hormones
4) As energy if sugar level in the blood drop.
5) Transport (transporter, singal receptor and ion channel)
6) Structure of the cell
7) Enzymes

Amino acid with Aliphatic Side Chains
1) Glycine
2) Alanine
3) Valine
4) Leucine
5) Isoleucine

Amino acid with Sulfur containing side chains
1) Cysteine
2) Methionine

Amino acid with Aliphatic Hydroxyl-Containing Side Chains
1) Serine
2) Threonine

Amino Acid with Acidic Side Chains and their derivatives
1) Aspartate
2) Glutamate
3) Asparagine
4) Glutamine

Classification
Carbohydrate has a general formula Cn(H2O)n. It can be classified into Monosaccharides, Disaccharides, Oligosaccharides and Polysaccharides.

Monosaccharides
It is the simplest sugar that make up Disccharides, Oligosccharides and Polysaccharides. Examples of 6 carbons sugar are glucose, galactose and fluctose. Examples of 5 carbon sugar are ribose and deoxyribose.

Oligosaccharides
It is the combination of 2 or more monosaccharides. If it is 2 monosaccharides, it is called disaccharide. Examples of disaccharide are sucrose (make up of one glucose and one fructose), maltose (make up of two glucoses), Lactose (make up of one galactose and one glucose). Example of oligosaccharide is raffinose which is made up of galactose, glucose and fructose.

Polysaccharides
However if the chain get too long perhaps a few hundred, we considered it as polysaccharide. Example are glycogen, cellulose and starch. Polysacharides normally do not have sweet taste compare to monosaccharide and disaccharide.

Classification
There are two types of cells mainly Eukaryotic and Prokaryotic. Animals, plants, fungi, and protists are eukaryotic while microorganism are prokaryote.

Eukaryotic cells
1) More complex DNA
2) Usually 10 times larger than Prokaryotic
3) Do not have cell wall
4) Have Membrane bounded organelle such as mitrochiondrion.
5) DNA is held in the nucleus

Prokaryote
1) Simple cell structure
2) Usually 10 time smaller than Eukaryotic
3) Has a cell wall that is made up of peptidoglycan
4) No intracellular and do not have membrane bounded organelle
5) DNA float freely in cell