What is "vitamin"

Vitamin \Vit"a*min\ (v[imac]t"[.a]*m[i^]n), n. any of several organic chemical substances not synthesized by an animal and required in small quantities for normal metabolism, present in and obtained from the natural foods eaten by the animal. Human vitamins are also produced synthetically, and taken in pure form or in mixtures, as dietary supplements. Deficiencies of specific vitamins lead to certain specific disorders, such as scurvy, caused by an insufficiency of vitamin C (ascorbic acid).

Note: Most vitamins act as coenzymes or precursors to coenzymes, and are not consumed for energy production or incorporated into structural units of the cell.

1920, originally vitamine (1912) coined by Polish biochemist Casimir Funk (1884-1967), from Latin vita "life" (see vital) + amine, because they were thought to contain amino acids. The terminal -e formally was stripped off when scientists learned the true nature of the substance; -in was acceptable because it was used for neutral substances of undefined composition. The lettering system of nomenclature (Vitamin A, B, C, etc.) was introduced at the same time (1920).

n. Any of a specific group of organic compounds essential in small quantities for healthy human growth, metabolism, development, and body function; found in minute amounts in plant and animal foods or sometimes produced synthetically; deficiencies of specific vitamins produce specific disorders.

n. any of a group of organic substances essential in small quantities to normal metabolism

By convention the term vitamin includes neither other essential nutrients, such as dietary minerals, essential fatty acids, or essential amino acids (which are needed in greater amounts than vitamins) nor the great number of other nutrients that promote health, and are required less often to maintain the health of the organism. Thirteen vitamins are universally recognized at present. Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" refers to a number of vitamer compounds that all show the biological activity associated with a particular vitamin. Such a set of chemicals is grouped under an alphabetized vitamin "generic descriptor" title, such as " vitamin A", which includes the compounds retinal, retinol, and four known carotenoids. Vitamers by definition are convertible to the active form of the vitamin in the body, and are sometimes inter-convertible to one another, as well.

Vitamins have diverse biochemical functions. Some, such as vitamin D, have hormone-like functions as regulators of mineral metabolism, or regulators of cell and tissue growth and differentiation (such as some forms of vitamin A). Others function as antioxidants (e.g., vitamin E and sometimes vitamin C). The largest number of vitamins, the B complex vitamins, function as enzyme cofactors ( coenzymes) or the precursors for them; coenzymes help enzymes in their work as catalysts in metabolism. In this role, vitamins may be tightly bound to enzymes as part of prosthetic groups: For example, biotin is part of enzymes involved in making fatty acids. They may also be less tightly bound to enzyme catalysts as coenzymes, detachable molecules that function to carry chemical groups or electrons between molecules. For example, folic acid may carry methyl, formyl, and methylene groups in the cell. Although these roles in assisting enzyme-substrate reactions are vitamins' best-known function, the other vitamin functions are equally important.

Until the mid-1930s, when the first commercial yeast-extract vitamin B complex and semi-synthetic vitamin C supplement tablets were sold, vitamins were obtained solely through food intake, and changes in diet (which, for example, could occur during a particular growing season) usually greatly altered the types and amounts of vitamins ingested. However, vitamins have been produced as commodity chemicals and made widely available as inexpensive semisynthetic and synthetic-source multivitamin dietary and food supplements and additives, since the middle of the 20th century. Study of structural activity, function and their role in maintaining health is called vitaminology.