Minerals are inorganic substances that occur in nature. Many minerals are relevant to human nutrition, including water, sodium, potassium, chloride, calcium, phosphate, sulfate, magnesium, iron, copper, zinc, manganese, iodine, selenium, and molybdenum. Cobalt is a required mineral for human health, but itis supplied by vitamin B12. Cobalt appears to have no other function, aside from being part of this vitamin. There is some evidence that chromium, boron, and other inorganic elements play some part in human nutrition, but the evidence is indirect and not yet convincing. Fluoride seems not to be required for human life, but its presence in the diet contributes to long-termdental health. Some of the minerals do not occur as single atoms, but occuras molecules, which are composed of one or more atoms. These include water, phosphate, sulfate, and selenite (a form of selenium). Sulfate contains an atom of sulfur, and the body can acquire all the sulfate it needs from protein.

Various minerals, or inorganic nutrients, are required for life, meaning thattheir continued supply in the diet is needed for growth, maintenance of bodyweight in adulthood, and for reproduction. The amount of each mineral that is needed to support growth during infancy and childhood, to maintain body weight and health, and to facilitate pregnancy and lactation, are listed in a table called the Recommended Dietary Allowances (RDA), which was compiled by the United States Food and Nutrition Board. All of the values listed in the RDAindicate the daily amounts that are expected to maintain health throughout most of the general population. However, studies on small groups of healthy human subjects indicate that the actual levels of each inorganic nutrient required by any given individual is likely to be less than that stated by the RDA,which set the standards in order to accommodate the variability expected among the general population.

The RDAs for adult males are 800 mg of calcium, 800 mg of phosphorus, 350 mgof magnesium, 10 mg of iron, 15 mg of zinc, 0.15 mg of iodine, and 0.07 mg ofselenium. The RDA for sodium is expressed as a range (0.5-2.4 g/day). The minimal requirement for chloride is about 0.75 g/day, and the minimal requirement for potassium is 1.6-2.0 g/day, though RDA values have not been set for these nutrients. The RDAs for several other minerals has not been determined, and here the estimated safe and adequate daily dietary intake has been listedby the Food and Nutrition Board. These values are listed for copper (1.5-3.0mg), manganese (2-5 mg), fluoride (1.5-4.0 mg), molybdenum (0.075-0.25 mg), and chromium (0.05-0.2 mg). (The function of chromium is essentially unknown,and evidence for its necessity exists only for animals.)

People are treated with minerals for several reasons. The primary reason is to relieve a mineral deficiency such as iron deficiency anemia. Chemical testssuitable for the detection of all mineral deficiencies are available. The diagnosis of the deficiency is also often aided by non-chemical tests such as the hematocrit test for the red blood cell content in blood for iron deficiency, the visual examination of the neck for iodine deficiency, or the examination of bones by densitometry for calcium deficiency.

Mineral treatment can also help prevent the development of a possible or expected deficiency. Examples include the practice of giving young infants iron supplements and the food industry's practice of supplementing infant formulaswith iron. The purpose here is to reduce the risk for iron deficiency anemia.Another example is women taking calcium supplements with the hope of reducing the risk of osteoporosis.

There is reason to believe that the purchase and consumption of most, but notall, of these minerals is beneficial to health. Potassium supplements are useful for reducing blood pressure in cases of persons with high blood pressure. The effect of potassium varies from person to person. The consumption of calcium supplements is likely to have some effect on reducing the risk for osteoporosis. Selenium supplements are expected to be of value only for residentsof Keshan Province, China, because of the established association of selenium deficiency and "Keshan disease" in this region.

Minerals are used in medical treatments by replacing a poor diet with a dietthat supplies the RDA, by consuming oral supplements (commercially availablein stores), or by injections or infusions. Injections are especially useful for infants, for mentally disabled persons, or where the physician wants to betotally sure of compliance. Infusions, as well as injections, are essentialfor medical emergencies, as during mineral deficiency situations like hyponatremia (sodium deficiency), hypokalemia (potassium deficiency), hypocalcemia (calcium deficiency), and hypomagnesemia (magnesium deficiency). Oral mineralsupplements are especially useful for mentally alert persons who otherwise cannot or will not consume food that is a good mineral source, such as meat. For example, a vegetarian who! will not consume meat may be encouraged to consume oral supplements of iron, as well as supplements of vitamin B12.

Calcium supplements, along with naturally occuring hormones estrogen and calcitonin therapy, are commonly used in the prevention and treatment of osteoporosis. Fluoride has been proven to reduce the rate of tooth decay. Magnesium is often used to treat eclampsia, which occasionally occurs during pregnancy.In this case, magnesium is used as a drug (magnesium sulfate) to prevent convulsions, and not to relieve a deficiency. Treatment with cobalt, in the formof vitamin B12, is used for relieving the symptoms of pernicious anemia, a relatively common disease which tends to occur in persons older than40 years. Free cobalt is never used for the treatment of disease. The response to mineral treatment can be monitored by chemical tests, by an examinationof red blood cells or white blood cells, or by physiological tests, depe! nding on the exact mineral deficiency.

There are some risks associated with mineral treatment, and mineral toxicitycan be life theatening in some instances. Selenium, for example, is distinguished among most of the nutrients in that dietary intakes at levels only ten times that of the RDA can be toxic. In treating emergency cases of hyponatremia, hypokalemia, or hypocalcemia by intravenous injections, too much sodium, potassium, or calcium, can result in hypernatremia, hyperkalemia, or hypercalcemia, respectively. Risk for toxicity is rare where treatment is by dietary means because the intestines act as a barrier, and absorption of any mineral supplement is gradual. The gradual passage of any mineral through the intestines, especially when the mineral supplement is taken with food, allows the various organs of the body to acquire the mineral. Gradual passage of the mineral into the bl! oodstream also allows the kidneys to excrete the mineral in the urine, should levels of the mineral rise to toxic levels in the blood.

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