Mineral deficiency is a condition where the concentration of any one of the minerals essential to human health is abnormally low in the body. In some cases, an abnormally low mineral concentration is defined as that which leads toan impairment in a bodily function dependent on the mineral. In other cases,an abnormally low mineral concentration is defined as a level lower than thatfound in the healthy population.
Mineral nutrients are all the inorganic elements or inorganic molecules thatare required for life. As far as human nutrition is concerned, inorganic nutrients include water, sodium, potassium, chloride, calcium, phosphate,sulfate, magnesium, iron, copper, zinc, manganese, iodine, selenium, and molybdenum. There is some evidence that other inorganic nutrients, such as chromium and boron, also play a part in human health, but their role is not well established. Fluoride has been proven to increase the strength of bones and teeth, but there is little or no reason to believe that it is needed for human life.
Severe deficiencies in any one of the inorganic nutrients can result in specific symptoms and sometimes in death, due to the failure of functions associated with that nutrient. A deficiency in one nutrient may occur less often thandeficiency in several nutrients. A patient suffering from malnutrition is deficient in a variety of nutrients. In the United States, malnutrition is mostoften found among severe alcoholics. Deficiencies in one nutrient do occur,for example, in human populations living in iodine-poor regions of the worldand in iron-deficient persons who lose excess iron by abnormal bleeding.
Inorganic nutrients have a wide variety of functions in the body. Water, sodium, and potassium deficiencies are most closely associated with abnormal nerve action and cardiac arrhythmias. Deficiencies in these nutrients tend to result not from a lack of content in the diet, but from excessive losses due tosevere diarrhea and other causes. Iodine deficiency is a global public healthproblem. It occurs in parts of the world with iodine-deficient soils and results in goiter, which involves a relatively harmless swelling of the neck, and cretinism, a severe birth defect. The body uses iodine for making thyroid hormone. However, since thyroid hormone has a variety of roles in developmentof the embryo, iodine deficiency during pregnancy results in a number of birth defects.
Calcium deficiency due to lack of dietary calcium occurs only rarely. However, calcium deficiency due to vitamin D deficiency can be found among certain populations. Vitamin D is required for the efficient absorption of calcium from the diet, and vitamin D deficiency in growing infants and children can result in calcium deficiency.
Dietary phosphate deficiency is rare because phosphate is plentiful in plantand animal foods, but also because phosphate is efficiently absorbed from thediet into the body. Iron deficiency causes anemia (lack of red blood cells),which results in tiredness and shortness of breath.
Dietary deficiencies in the remaining inorganic nutrients tend to be rare. Magnesium deficiency tends to occur in chronic alcoholics, in persons taking diuretic drugs, and in those suffering from severe and prolonged diarrhea. Magnesium deficiency tends to occur with the same conditions that provoke deficiencies in sodium and potassium. Zinc deficiency has been found in poor MiddleEastern populations who rely on unleavened whole wheat bread as a major foodsource. Copper deficiency is also rare, but dramatic and health-threatening changes in copper metabolism occur in two genetic diseases, Wilson's disease and Menkes' disease.
Selenium deficiency may occur in regions of the world where the soils are poor in selenium, thus producing foods that are also low in this mineral. Premature infants may also be at risk for selenium deficiency. Manganese deficiencyis extremely rare.
Sodium deficiency (hyponatremia) and water deficiency are the most serious and widespread deficiencies in the world. These deficiencies tend to arise fromexcessive losses from the body, as during prolonged and severe diarrhea or vomiting. Diarrheal diseases are a major world health problem and are responsible for about a quarter of the 10 million infant deaths that occur each year.Nearly all of these deaths occur in impoverished parts of Africa and Asia due to contamination of the water supply by animal and human feces. The main concern in treating diarrheal diseases is dehydration, that is, the losses of sodium and water which deplete the fluids of the circulatory system (the heart, veins, arteries, and capillaries). Severe losses of the fluids of the circulatory system result in shock, which is defined as inadequate supply of bloodto the various tissues of the body resulting in a lack of oxygen to all of the body's cells. The main concern in avoiding shock is the replacement of sodium and water.
Sodium deficiency and potassium deficiency also frequently result during treatment with drugs called diuretics, which are used to treat high blood pressure (hypertension). However, diuretics can lead to sodium deficiency, excessiveloss of potassium, and low plasma potassium (hypokalemia).
Iodine deficiency tends to occur in regions of the world where the soil is poor in iodine. Goiter, an enlargement of the thyroid gland (located in the neck), results from iodine deficiency. Goiter continues to be a problem in eastern Europe, parts of India and South America, and in Southeast Asia. Goiter has been eradicated in the United States because of the fortification of foodswith iodine. Iodine deficiency during pregnancy results in cretinism in the newborn. Cretinism involves mental retardation, a large tongue, and sometimesdeafness, muteness, and lameness.
Iron deficiency occurs due to periods of dietary deficiency, rapid growth, and excessive loss of the body's iron. Infants are at risk for acquiring iron deficiency because their rapid rate of growth needs a corresponding increasedsupply of dietary iron for use in making blood and muscles. Human milk is a better source of iron than cow milk, since about half of the iron in human breast milk is absorbed by the infant's digestive tract. In contrast, only 10% of the iron in cow milk is absorbed by the infant. Surveys of lower-income families in the United States have revealed that about 6% of the infants are anemic indicating a deficiency of iron in their diets. Blood loss that occurs with menstruation in women, as well as with a variety of causes of intestinal bleeding, is a major cause of iron deficiency. The symptoms of iron deficiencyare generally limited to anemia and the resulting tiredness, weakness, and areduced ability to perform physical work.
Calcium and phosphate are closely related nutrients. About 99% of the calciumand 85% of the phosphate in the body occur in the skeleton. Both of these nutrients occur in a great variety of foods, especially milk, eggs, and green,leafy vegetables are rich in calcium and phosphate. Dietary deficiencies in calcium (hypocalcemia) or phosphate are extremely rare throughout the world. Vitamin D deficiency can be found among young infants, the elderly, and otherswho may be shielded from sunshine for prolonged periods of time. Vitamin D deficiency impairs the absorption of calcium from the diet and, as a result, can provoke calcium deficiency even when the diet contains adequate calcium.
Zinc deficiency has been found among peasant populations in rural areas of the Middle East. Unleavened whole wheat bread can account for 75% of the energyintake in these areas. This diet, which does not contain meat, does containzinc, but it also contains phytic acid, which naturally occurs in wheat and inhibits zinc absorption. The yeast used to leaven bread produces enzymes thatinactivate the phytic acid. Unleavened bread does not contain yeast and, therefore, contains intact phytic acid. The symptoms of zinc deficiency includelack of sexual maturation, lack of pubic hair, and small stature. Zinc deficiency is relatively uncommon in the United States, but it may occur in adultswith alcoholism or intestinal malabsorption problems. Low plasma zinc has been found in patients with alcoholic cirrhosis, Crohn's disease, and celiac disease. The signs of zinc deficiency include a rash on the face, groin, hands,and feet and diarrhea. These symptoms can easily be reversed by administeringzinc. An emerging concern is that increased calcium intake can interfere with zinc absorption or retention. Hence, there is some interest in the questionof whether persons taking calcium to prevent osteoporosis should also take zinc supplements.
Severe alterations in copper metabolism occur in two genetic diseases, Wilson's disease and Menkes' disease. Both of these diseases are rare and occur inabout one in 100,000 births.
Selenium deficiency may occur in premature infants, since this population naturally tends to have low levels of plasma selenium. Selenium deficiency occurs in regions of the world containing low-selenium soils. These regions include Keshan Province in China, New Zealand, and Finland. In Keshan Province, a disease (Keshan disease) occurs which results in deterioration of regions of the heart and the development of fibers in these regions.
Minerals serve strikingly different functions in the body, and the tests forthe corresponding deficiency are markedly different from each other. The mineral content of the body may be measured by testing samples of blood plasma, red blood cells, or urine. In the case of calcium and phosphate deficiency, the diagnosis may also involve taking x rays of the skeleton. In the case of iodine deficiency, the diagnosis may include examining the patient's neck withthe eyes and hands. In the case of iron deficiency, the diagnosis may includethe performance of a stair-stepping test by the patient.
In the healthy population, all mineral deficiencies can be prevented by the consumption of inorganic nutrients at levels defined by the RDA. Where a balanced diet is not available, government programs for treating individuals, or for fortifying the food supply, may be used. Ensuring an adequate intake of these minerals, by eating a balanced diet or by taking mineral supplements, isthe best way to prevent deficiencies.