any of a group of inorganic elements that are essential to humans and animals for normal body function. In nutrition, minerals are those elements for which the body's requirement is at least 100 mg per day, and trace minerals are those elements that are needed in smaller amounts. Dietary minerals are derived from the earth's crust. Plants extract the minerals from the soil, and humans and animals, in their turn, consume the plants. There are seven major minerals. Calcium occurs mainly in the teeth and bones, but a small amount is found in blood plasma and other body fluids, where it influences nerve transmission, blood clotting, and muscle contraction. Dairy products and green leafy vegetables are dietary sources of calcium, and an adequate intake of vitamin D is required for calcium absorption. Phosphorus, also found in dairy products, is closely allied to calcium in bone and tooth formation and its association with vitamin D. It is present in every cell in compounds such as nucleic acids and adenosine triphosphate. Magnesium, also present in every cell, is necessary for carbohydrate and protein metabolism, cell reproduction, and smooth muscle action. Dietary sources include nuts, soy beans, and cocoa. Sodium is in the skeleton and extracellular fluids and is necessary for fluid and acid-base balance, cell permeability, and muscle function. It occurs in table salt ( sodium chloride, the main source) and such foods as milk and spinach. Potassium, which is found in intra- and extracellular fluid, plays a major role in fluid and electrolyte balance and in heart muscle activity, and is also required for carbohydrate metabolism and protein synthesis. Its sources include legumes, whole grains, and bananas. Chlorine is found in extracellular fluid, where it helps maintain normal fluid-electrolyte and acid-base balance, and in the stomach, where it helps provide the acidic environment necessary for digestion. Table salt is its main dietary source. Sulfur, which is important to the structure of proteins, is also necessary for energy metabolism, enzyme function, and detoxification. Sulfur is obtained from protein foods, such as meat, eggs, and legumes. Some trace minerals are considered "essential" in human nutrition. The essential trace minerals include iron, which is a constituent of hemoglobin ; iodine, which is necessary for thyroxine synthesis; and cobalt, which is a component of vitamin B ₁₂. Other essential trace minerals are chromium, copper, fluorine, manganese, molybdenum, selenium, and zinc.

The Columbia Encyclopedia, Sixth Edition Copyright© 2004, Columbia University Press. Licensed from Lernout & Hauspie Speech Products N.V. All rights reserved.

-31765-