Dietary minerals (min′er-alz) are inorganic elements essential in human metabolism. Plants usually extract these elements from soil, and humans obtain them from plant foods or from animals that have eaten plants.
Characteristics of Minerals
Minerals contribute about 4% of body weight and are most concentrated in the bones and teeth. Minerals are usually incorporated into organic molecules. For example, phosphorus is found in phospholipids, iron in hemoglobin, and iodine in thyroxine. However, some minerals are part of inorganic compounds, such as the calcium phosphate of bone. Other minerals are free ions, such as sodium, chloride, and calcium ions in blood. Minerals are parts of the structural materials of all body cells. They also constitute parts of enzyme molecules, contribute to the osmotic pressure of body fluids, and play vital roles in nerve impulse conduction, muscle fiber contraction, blood coagulation, and maintenance of the pH of body fluids.
Calcium and phosphorus account for nearly 75% by weight of the mineral elements in the body. Therefore, they are termed major minerals. Other major minerals, each of which accounts for 0.05% or more of the body weight, include potassium, sulfur, sodium, chlorine, and magnesium. Table lists the distribution, functions, sources, and adult RDAs of major minerals.
Trace elements are essential minerals found in minute amounts, each making up less than 0.005% of adult body weight. They include iron, manganese, copper, iodine, cobalt, zinc, fluorine, selenium, and chromium. Table lists the distribution, functions, sources, and adult RDAs of the trace elements.