![]() |
Vitamins are nutrients required in very small amounts for essential metabolic reactions 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 strictly essential.
Vitamins are biomolecules that act both as catalysts and substrates in chemical reactions. When acting as a catalyst, vitamins are bound to enzymes and are called cofactors. (For example, vitamin K forms part of the proteases involved in blood clotting.) Vitamins also act as coenzymes to carry chemical groups between enzymes. (For example, folic acid carries various forms of carbon groups–methyl, formyl or methylene–in the cell.)
Until the 1900s, vitamins were obtained solely through food intake. Many food sources contain different ratios of vitamins. Therefore, if the only source of vitamins is food, changes in diet will alter the types and amounts of vitamins ingested. However, as many vitamins can be stored by the body, short-term deficiencies (which, for example, could occur during a particular growing season) do not usually cause disease.