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Vitamins are carbon-containing substances that are required for normal metabolism but are not synthesized in the body; they ar
Vitamins are carbon-containing substances that are required for normal metabolism but are not synthesized in the body; they are obtained, therefore, from such outside sources as food and water or are administered orally or intravenously. Exceptions to this definition include vitamin D, which is synthesized in the body to a limited extent, and vitamin B(12), which is synthesized by bacterial flora in the intestinal tract.Vitamins and minerals function as "cofactors" in the metabolism of products in the body. Most aspects of bodily metabolism proceed with the aid of specific enzymes but if additional catalysts were not present, for example, the cofactor vitamins and minerals, the reactions would proceed so slowly that they would be ineffective.RDAMost authorities assume that all the human vitamin and mineral requirements have been discovered; it is possible, therefore, to predict accurately the vitamin and mineral requirements of humans for health and prevention of disease. In the United States a Food and Nutrition Board was established for the purpose of determining vitamin and mineral requirements. This board is composed of distinguished scientists and nutritionists and is under the auspices of the National Research Council of the National Academy of Sciences. Since 1940 the board has periodically prepared a brochure listing the "Recommended Dietary Allowances" (RDA) of vitamins and other nutrients, based on existing knowledge.These allowances are intended as a guide for nutritionists, institutional dietitians, and homemakers in planning food supplies and in the interpretation of food consumption levels. The RDA figures, however, are estimations based on the present state of knowledge of the needs of most human beings; particular requirements will be less or more, depending on numerous individual factors such...