Vitamin
hideA vitamin is an organic compound required as a nutrient in tiny amounts by an organism. A compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and the particular organism. For example, ascorbic acid functions as vitamin C for some animals but not others, and vitamins D and K are required in the human diet only in certain circumstances. The term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids, nor does it encompass the large number of other nutrients that promote health but are otherwise required less often.
Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" may refer to several vitamer compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals are grouped under an alphabetized vitamin "generic descriptor" title, such as "vitamin A," which includes the compounds retinal, retinol, and many carotenoids. Vitamers are often inter-converted in the body.
Vitamins have diverse biochemical functions, including function as hormones (e.g. vitamin D), antioxidants (e.g. vitamin E), and mediators of cell signaling and regulators of cell and tissue growth and differentiation (e.g. vitamin A). The largest number of vitamins (e.g. B complex vitamins) function as precursors for enzyme cofactor bio-molecules (coenzymes), that help act as catalysts and substrates in metabolism. When acting as part of a catalyst, vitamins are bound to enzymes and are called prosthetic groups. For example, biotin is part of enzymes involved in making fatty acids. Vitamins also act as coenzymes to carry chemical groups between enzymes. For example, folic acid carries various forms of carbon group – methyl, formyl and methylene - in the cell. Although these roles in assisting enzyme reactions are vitamins' best-known function, the other vitamin functions are equally important.
Until the 1900s, vitamins were obtained solely through food intake, and changes in diet (which, for example, could occur during a particular growing season) can alter the types and amounts of vitamins ingested. Vitamins have been produced as commodity chemicals and made widely available as inexpensive pills for several decades, allowing supplementation of the dietary intake.
For more information about Vitamin, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with vitamin
Vitamin D a key player in overall health of several body organs, says UC Riverside biochemist
Oct 09, 2008 |
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Essential for life in higher animals, vitamin D, once linked to only bone diseases such as rickets and osteoporosis, is now recognized as a major player in contributing to overall human health, emphasizes UC Riverside's Anthony ...
Vitamin C lowers levels of inflammation biomarker considered predictor of heart disease
Nov 13, 2008 |
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A new study led by researchers at the University of California, Berkeley, adds to the evidence that vitamin C supplements can lower concentrations of C-reactive protein (CRP), a central biomarker of inflammation that has ...
Vitamin B3 reduces Alzheimer's symptoms, lesions
Nov 04, 2008 |
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An over-the-counter vitamin in high doses prevented memory loss in mice with Alzheimer's disease, and UC Irvine scientists now are conducting a clinical trial to determine its effect in humans.
Low vitamin D levels pose large threat to health
Aug 11, 2008 |
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Researchers at Johns Hopkins are reporting what is believed to be the most conclusive evidence to date that inadequate levels of vitamin D, obtained from milk, fortified cereals and exposure to sunlight, lead to substantially ...
Optimal dose of vitamin E maximizes benefits, minimizes risk
Oct 30, 2008 |
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Vitamin E has been heralded for its ability to reduce the risk of blood clots, heart attack, and sudden death. Yet in some people, vitamin E causes bleeding. Scientists have known for more than 50 years that excess vitamin ...
Vitamin B12 may protect the brain in old age
Sep 08, 2008 |
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Vitamin B12, a nutrient found in meat, fish and milk, may protect against brain volume loss in older people, according to a study published in the September 9, 2008, issue of Neurology, the medical journal of the American Academ ...
Study helps clarify role of vitamin D in cancer therapy
Nov 17, 2008 |
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A colon cancer cell isn't a lost cause. Vitamin D can tame the rogue cell by adjusting everything from its gene expression to its cytoskeleton. In the Nov. 17 issue of the Journal of Cell Biology, Ordóñez-Morán et al. sh ...
Lack of vitamin D linked to Parkinson's disease
Oct 13, 2008 |
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A majority of Parkinson's disease patients had insufficient levels of vitamin D in a new study from Emory University School of Medicine.
Oral vitamin D may help prevent some skin infections
Oct 06, 2008 |
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A study led by researchers at the University of California, San Diego School of Medicine suggests that use of oral Vitamin D supplements bolsters production of a protective chemical normally found in the skin, and may help ...
Diet key to blood pressure
Feb 06, 2009 |
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If you're like many Americans, your blood pressure has crept up as you've gotten older. But it doesn't have to. Our lifestyle has an impact on blood pressure; in fact, in parts of the world where people still live as their ...
Forget the antioxidants? Researchers cast doubt on role of free radicals in aging
Biology /
Feb 17, 2009 |
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For more than 40 years, the prevailing explanation of why we get old has been tied to what is called oxidative stress. This theory postulates that when molecules like free radicals, oxygen ions and peroxides build up in cells, ...
Could vitamin D save us from radiation?
Nov 07, 2008 |
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Radiological health expert Daniel Hayes, Ph.D., of the New York City Department of Health and Mental Hygiene suggests that a form of vitamin D could be one of our body's main protections against damage from low levels of ...
Vitamin D found in fish boosts brain power
May 21, 2009 |
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Eating fish -- long considered 'brain food' -- may really be good for the old grey matter, as is a healthy dose of sunshine, new research suggests.
Health Tip: Are Vitamin Supplements Worthwhile or Not?
Feb 16, 2009 |
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(PhysOrg.com) -- You may be wondering at this point whether to toss those vitamins into your mouth or into the trash. That's not surprising since several recent reports have called the value of vitamins into question, leaving ...
Successful weight loss with dieting is linked to vitamin D levels
Jun 11, 2009 |
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Vitamin D levels in the body at the start of a low-calorie diet predict weight loss success, a new study found.
