About 4% of the total weight of the body is made up of inorganic or mineral elements, chiefly calcium and phosphorus. Still, there is enough iron to make a good size nail and enough sodium for a small shaker of table salt. In general, the minerals are regulators of metabolic processes. The fourteen so-called mineral elements deemed essential in human nutrition are calcium, phosphorus, iron, sodium, zinc, copper, potassium, sulfur, manganese, magnesium, cobalt, iodine, fluorine and chlorine. "Trace amounts" of other minerals such as aluminum, silicon, and nickel are also present.
From the standpoint of human diet, however, we must give the most important consideration to the three mineral elements which are most likely to be lacking in the American diet—namely calcium, iron, and iodine. When these elements are supplied from natural food sources, the other mineral elements needed are also likely to be present. A good variety of common foods supplies required minerals in adequate quantities. The body stores and utilizes them well.
Calcium plays many roles. It is essential to the growth, development, and maintenance of bones and teeth. It is necessary to the clotting of the blood. It helps to regulate the heartbeat, to maintain the acid-base balance in the body, and to control the irritability of the neuromuscular system.
Calcium is needed throughout life, but is most important in the early years. The richest source of calcium in the human diet is milk — mother's, cow's, goat's, camel's, or mare's. Another good source is shellfish.
Phosphorus likewise is essential for the development of the bony structure of the body and the regulation of acid-base balance. In many respects calcium and phosphorus play complementary roles. Phosphorus plays an added role in carbohydrate and fat metabolism. Phosphorus is widely distributed in many foodstuffs, often in the form of phosphates. If calcium intake is adequate, phosphorus usually comes along with it.
Iron in the human body is concentrated largely in the blood and blood-forming organs, chiefly the bone marrow. It is an essential constituent of hemoglobin the crucial element in the red blood cells. It is needed for the transport of oxygen by the red blood cells.
Actually, the amount of iron required by the body is small only a few specks, equivalent to the daily intake of about 12 milligrams. Variety meats, like liver, are the best sources of iron.
Copper, as a dietary essential, usually goes along with iron, but only about one-quarter as much as needed. Sodium and potassium are another pair of minerals that complement each other's effects in cell and body metabolism; they are importantly concerned with water balance. Sodium is found in common table salt, along with chlorine that appears as hydrochloric acid in the stomach juices. Iodine is essential for the manufacture of thyroxin by the thyroid gland- Iodine is found in seafood and it is added to common table salt in the form of potassium iodide.