Vitamins were discovered by Dutch physician, Christiaan Eijkmann, who won the 1929 Nobel prize in physiology and medicine. Vitamins are essential for life and contribute to good health by regulating metabolism and assisting the biochemical processes that release energy from digested foods. Therefore, a "vitamin" is any of the organic compounds required by the body in small amounts (micronutrients), to protect health and for proper growth in living creatures.

Vitamins also assist in the formation of hormones, blood cells, nervous-system chemicals, and genetic material. The various vitamins are not chemically related, and most differ in their physiological actions. They generally act as catalysts, combining with proteins to create metabolically active enzymes that in turn produce hundreds of important chemical reactions throughout the body. Without vitamins, many of these reactions would slow down or cease. The intricate ways in which vitamins act on the body, however, are still far from clear.

The 13 well-identified vitamins are classified according to their ability to be absorbed in fat or water. The fat-soluble vitamins include vitamin A, vitamin D, vitamin E, and vitamin K. These are generally consumed along with fat-containing foods. Because they can be stored in the body's fat, they do not have to be consumed every day. The water-soluble vitamins include the eight B vitamins and vitamin C. These cannot be stored by the body and must be consumed frequently, preferably every day.

Only vitamin D can be manufactured by the body. All others must be derived from the diet. Lack of sufficient vitamin intake causes a wide range of health problems and dysfunctions. The U.S. Food and Nutrition Board of the National Research Council has published recommended dietary allowances (RDA) for vitamins, minerals, and other nutrients. RDAs are normally expressed in international units (IU) or milligrams. For adults and children of normal health, these recommendations are useful guidelines not only for professionals in nutrition but also for the growing number of families and individuals who eat irregular meals and rely on prepared foods (many of which are now required to carry nutritional labeling). Unfortunately, these RDAs give only the bare minimum required to ward off deficiency diseases such as rickets, beri-beri, scurvy, and night blindness. What they do not account for are the amounts needed to maintain maximum health.

All vitamin supplements work best when taken along with food. Typically, oil-soluble vitamins should be taken before meals and water soluble vitamins should be taken after meals. 

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