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Vitamin B

Pyridoxine (Vitamin-B6).
Vitamin B6 is an essential water-soluble B vitamin. It exists in plants and animals in several forms (termed vitamers) that are interchangeable and comparably active. The chemical form typically provided in vitamin supplements is pyridoxine hydrochloride (or pyridoxine HCl).
 
Like all true vitamins, B6 functions as a coenzyme, meaning that it works in tandem with one or more enzymes to catalyze metabolic reactions in cells. Vitamin B6, in fact, serves as a cofactor for over 100 enzymes in the human body, many of which are involved in amino acid metabolism. The types of enzymatic reactions that vitamin B6 is involved with include the transamination, decarboxylation, cleavage, racemization, and synthesis of amino acids.
 
Because these reactions are central to the function of all cells, vitamin B6 ultimately plays a central role in human metabolism and health. Primary processes mediated by vitamin B6 include the generation of glucose from glycogen, the synthesis of niacin (vitamin B3), lipid metabolism, nervous system function, hormone modulation, and immune function.
 
Vitamin B6 also affects nervous system function, largely through its role in the synthesis of the neurotransmitters serotonin, taurine, dopamine, norepinephrine, and dopamine. It also appears to be involved in the development of myelin sheaths.
 
Given its central role in amino acid metabolism, vitamin B6 is important in regulating homocysteine levels in blood, which in turn constitutes an important risk factor for cardiovascular disease and stroke. Folic acid and vitamin B12 are also involved in the regulation of homocysteine.
 
Vitamin B2 (riboflavin), niacin, and zinc are required for vitamin B6 activation and metabolism.
 
The best food sources of vitamin B6 include whole grain cereals, poultry and other meat, nuts, and seeds. Fruits and vegetables are not generally good sources with the exception of potatoes, bananas, and avocados.
 
Unlike other water-soluble vitamins, a chronic intake (exceeding 200 mg/d) of vitamin B6 has been associated with adverse effects, including neurological toxicity.
 
For additional information (including a list of references), please refer to the vitamin B6 technical bulletin at http://www.usana.com/dotCom/company/science/components.
 
Additional Resources:
 
Dietary Supplement Fact Sheet: Vitamin B6 (from the National Institute of Health)
 
Vitamin B6 - U.S. National Library of Medicine
 
Vitamin B6 - Physicians' Desktop Reference
 
Vitamin B6 - Mayo Clinic
 
Vitamin B6 - Linus Pauling Institute
 
Vitamin B6 - Wikipedia