vitamin is a nutrient that is an organic compound required in tiny amounts for
essential metabolic reactions in a living organism.[1] Most vitamins cannot be
obtained in sufficient quantities by synthesis in the body, and therefore must
be obtained from the diet. Thus, the term is conditional on the circumstances
and the particular living 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.[2] Vitamins are defined by their
biological activity, not their structure. Thus, each "vitamin" actually refers
to a number of vitamer compounds, which form a set of distinct chemical
compounds that show the biological activity of a particular vitamin. Such a set
of chemicals are grouped under an alphabetized vitamin "generic descriptor"
title, such as "vitamin A," which (for example) includes retinal, retinol, and
many carotenoids. [3] Vitamers are often inter-convertible in the body. 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 that are not essential for
life.
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)
[4]. 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.[5]
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,[6] allowing supplementation of the dietary intake.
Calcium Ascorbate (119)
Ester-C (623)
K-Mag (17)
Multivitamins (3,558)
Vitamin A (436)
Vitamin B (3,729)
Vitamin C (2,474)
Vitamin D (197)
Vitamin E (2,675)
Vitamin K1 (53)
Vitamin O (29)
Vitamin B4 Adenine DNA metabolite
Vitamin B8 Adenylic acid DNA metabolite
Vitamin F Essential fatty acids Needed in large quantities (does
not fit the definition of a vitamin).
Vitamin G Riboflavin Reclassified as Vitamin B2
Vitamin H Biotin Reclassified as Vitamin B7
Vitamin J Catechol, Flavin Protein metabolite
Vitamin L1[32] Anthranilic acid Protein metabolite
Vitamin L2[32] Adenylthiomethylpentose RNA metabolite
Vitamin M Folic acid Reclassified as Vitamin B9
Vitamin O Carnitine Protein metabolite
Top Brands
Alacer
Appearex
Aubrey Organics
Avalon
Bausch & Lomb
Carlson
Centrum
Childlife
Colonial Dames
Country Life
DEVA NUTRITION LLC
Emergen-C
Enfamil
Ester-C
Fiber 35 Diet
Flexcin
Flintstones
Folgard
Fruit of the Earth
Garden Of Life
High Performance
ICaps
Kirkland
Lil Critters
Liquid Health
Liquimax
Lumina Health
Natrol
Nature Made
Nature's Bounty
Nature's Plus
Nature's Way
New Chapter Nexxus
Nordic Naturals
Now Foods
One-A-Day
Prevagen
PureGels
Rainbow Light
RoC
Slo-Niacin
Solgar
Source Naturals
Sundown
Swanson Health Products
TwinLab
Twinlab
Viactiv
Vitalert
Weil Nutritionals
|
