Vitamins and Minerals

Most vitamins and all minerals are essential nutrients. That is, they cannot be synthesized by the body and so must be consumed in the diet.

Vitamins are classified as water soluble--vitamin C and the eight members of the vitamin B complex--or fat soluble--vitamins A, D, E, and K.

Some minerals are required in fairly large quantities (about 1 or 2 grams a day) and are considered macronutrients. They include calcium, chloride, magnesium, phosphorus (occurring mainly as phosphate in the body), potassium, and sodium. Minerals required in small amounts are considered micronutrients and are called trace minerals. They include copper, fluoride, iodine, iron, selenium, and zinc. Except for fluoride, all of these minerals activate enzymes required in metabolism. Fluoride forms a stable compound with calcium, helping stabilize the mineral content of bones and teeth and helping prevent tooth decay. Trace minerals such as arsenic, chromium, cobalt, nickel, silicon, and vanadium, which may be essential in animal nutrition, have not been established as requirements in human nutrition. All trace minerals are toxic at high levels, and some (arsenic, nickel, and chromium) have been identified as causes of cancer.

Some vitamins and minerals (such as vitamins C and E and selenium) act as antioxidants, as do other substances in fruits and vegetables (such as beta-carotene). Antioxidants protect cells against damage by free radicals, which are reactive by-products of the normal activity of cells. Free radicals are thought to contribute to such disorders as heart disease and cancer. People who eat adequate amounts of fruits and vegetables, which are rich in antioxidants, are less likely to develop heart disease and certain cancers. However, whether these benefits are due to antioxidants, other substances in the fruits and vegetables, or other factors is not known.