Mineral deficiency

Definition

Mineral deficiency is a reduced level of any of the minerals essential to human health. An abnormally low mineral concentration is usually defined as a level that may impair a function dependent on that mineral.

Description

Minerals are essential nutrients for every living cell in the human body. Defined in the study of human nutrition as all the inorganic elements or molecules required for life, minerals assist in body functions such as producing energy, growing, and healing. Minerals are required for fluid balance, blood and bone development, maintaining a healthy nervous system, and regulating muscles, including heart muscles. Minerals, like vitamins , function as coenzymes. They participate in all enzyme reactions in the body and help in the assimilation and use of vitamins and other nutrients.

Minerals occur either as bulk minerals (macrominerals) or trace minerals (microminerals). The body needs more bulk minerals than it does trace minerals, although both are essential for health. Minerals are consumed in food from plants and plant-eating animals. These sources of minerals develop in a sequence that takes millions of years, beginning with rock formation, the breakdown of rocks into mineral salts, and the assimilation of these salts into soil that nourishes edible plants.

Recommended daily allowances exist for a number of minerals, such as calcium. However, minimum daily requirements for some minerals such as boron, chromium, and molybdenum, do not exist. The essential bulk minerals include:

• Calcium—essential for strong bones and teeth, healthy gums, and bone growth and mineral density in children. Calcium helps regulate the heart rate and nerve impulses, lower cholesterol, prevent atherosclerosis, develop muscles, and prevent muscle cramping. Calcium is an important component of blood clotting. Calcium and phosphorus are closely related minerals that should be balanced. About 99 percent of calcium and 85 percent of phosphate occur in the skeleton as crystals of calcium phosphate. Both nutrients occur in a variety of foods such as milk, eggs, and green, leafy vegetables. Calcium deficiency due to lack of dietary calcium occurs only rarely and is often due to vitamin D deficiency , because vitamin D is required for efficient absorption of dietary calcium. Significant depletion of calcium stores can lead to osteoporosis.
• Magnesium—assists in the utilization of calcium and potassium, and functions in enzyme reactions to produce energy. Magnesium protects the lining of arteries and helps form bones. It helps prevent cardiovascular disease, osteoporosis, and some cancers. By acting with vitamin B₆, magnesium can help prevent or dissolve calcium oxylate kidney stones, the most common kind of stones. Dietary magnesium deficiency is uncommon, but may occur in chronic alcoholics, persons taking diuretic drugs, and as a result of severe, prolonged diarrhea .
• Sodium—sodium deficiency (hyponatremia) is a serious deficiency, arising most often after excessive losses of body fluid (dehydration ) during prolonged and severe diarrhea or vomiting . Sodium and potassium are electrolytes that must be balanced in the body. Since most people get more than enough salt in the diet, potassium may be needed to balance it. Together, these minerals control fluid balance through a mechanism called "the sodium/potassium pump." Prolonged imbalances in sodium and potassium can contribute to heart disease.
• Potassium—important for a healthy nervous system and a steady heart rate, helps to prevent stroke , and, with sodium, is critical in maintaining fluid balance. Potassium, an electrolyte, must be balanced with sodium. Potassium deficiency is usually associated with sodium deficiency and both are associated with dehydration stemming from excessive losses of body fluid.
• Phosphorus—helps form bones and teeth, supports cell growth, and regulates heart muscle contraction and kidney function. Phosphorus converts food to energy and supports the utilization of vitamins. Deficiency is rare because phosphate is plentiful in plant and animal foods and is efficiently absorbed from the diet. Phosphorus is closely related to calcium and the two minerals should be in balance with each other and with magnesium. Deficiency in one will affect all and will ultimately have an unwanted effect on body function. Calcium and phosphorus are stored in the bones as crystals of calcium phosphate. Milk, eggs, and green, leafy vegetables are rich in calcium and phosphate.

Trace minerals essential for human health include:

• Boron—required for healthy bones, brain function, alertness, and the metabolism of bulk minerals such as calcium, phosphorus, and magnesium. Deficiencies are rare except in aging, when supplementation may help absorb calcium. A deficiency in boron is associated with vitamin D deficiency. Boron supplements can improve calcium levels as well as vitamin D levels, and can help prevent osteoporosis in postmenopausal women by promoting calcium absorption.
• Chromium—required for maintaining energy levels. Chromium helps metabolize glucose and stabilize glucose levels. It helps the body manufacture and use cholesterol and protein.
• Copper—helps form healthy bones, joints, and nerves as well as hemoglobin and red blood cells. Copper contributes to healing, energy production, taste, and hair and skin color. It is essential in forming collagen for healthy bones and connective tissue, and helps prevent osteoporosis. Except in osteoporosis, copper deficiency is rare, although dramatic changes in copper metabolism occur in two serious genetic diseases, Wilson disease and Menkes' disease.
• Germanium—helps improve the delivery of oxygen to tissues and remove toxins and poisons from the body. Germanium gives garlic its natural antibiotic properties.
• Iodine—helps promote healthy physical and mental development in children. Iodine is required for thyroid gland function and metabolizing fats. Iodine deficiency is a public health problem in parts of the world that have iodine-deficient soils. Iodine is needed to make thyroid hormone, which has a variety of roles in human embryo development. A deficiency during pregnancy can cause serious birth defects. Deficiency in adults can result in an enlarged thyroid gland (goiter) in the neck.
• Iron—critical in the production of hemoglobin, the oxygen-carrying protein in red blood cells, and myoglobin found in muscle tissue. Iron is essential for important enzyme reactions, growth, and maintaining a healthy immune system. In the blood, iron is found in larger amounts than any other mineral. Iron deficiency causes anemia (low hemoglobin and reduced numbers of red blood cells), which results in tiredness and shortness of breath because of poor oxygen delivery.
• Manganese—essential for metabolizing fat and protein, regulating blood glucose, and supporting immune system and nervous system function. Manganese is necessary for normal bone growth and cartilage development. It is involved in reproductive functions and helps produce mother's milk. Along with B vitamins, manganese produces feelings of well-being. Deficiency can lead to convulsions, vision and hearing problems, muscle contractions, tooth-grinding and other problems in children; and atherosclerosis, heart disease, and hypertension in older adults.
• Molybdenum—found in bones, kidneys, and liver. Only extremely small amounts are needed to metabolize nitrogen and promote proper cell function. Molybdenum is present in beans, peas, legumes, whole grains, and green leafy vegetables. A diet low in these foods can lead to mouth and gum problems and cancer.
• Selenium—an important antioxidant that works with vitamin E to protect the immune system, heart, and liver, and may help prevent tumor formation. Selenium deficiency occurs in regions of the world where soils are selenium-poor and low-selenium foods are produced. Premature infants are naturally low in selenium with no known serious effects.
• Silicon—helps form bones and connective tissue, nails, skin, and hair. Silicon is important in preventing cardiovascular disease.
• Sulfur—disinfects the blood and helps to rid the body of harmful bacteria and toxic substances.
• Vanadium—vital to cell metabolism, and helps reduce cholesterol and form healthy bones and teeth. Vanadium functions in reproduction. Deficiencies may be associated with heart and kidney disease and reproductive disorders. Vanadium deficiency may be associated with infant mortality.
• Zinc—important in the growth of reproductive organs and regulation of oil glands. Zinc is required for protein synthesis, immune system function, protection of the liver, collagen formation, and wound healing. A component of insulin and major body enzymes, zinc helps vitamin absorption, particularly vitamins A and E. Deficiency is rare.

Trace and bulk minerals are stored in muscles and bones and delivered to tissue cells through blood circulation. They work together synergistically and must be chemically balanced in the body; if one is deficient or out of balance, it can affect all the others, often resulting in illness. If zinc, for example, is present at high levels, calcium levels will be reduced because the two minerals compete for absorption. Similarly, too much calcium will deplete magnesium, and so on. Deficiency in one nutrient occurs less often than deficiency in several nutrients. A child suffering from malnutrition will likely be deficient in a variety of nutrients. Deficiencies in one nutrient do occur, however, such as in populations living in iodine-poor regions, and in iron deficient persons who lose excess iron by abnormal bleeding. All uncorrected mineral deficiencies can affect body functions, produce symptoms, and result in illness.

Demographics

Statistics are not available for most individual mineral deficiencies, most likely because such deficiencies are rare in the United States. Surveys of lower-income families in the United States reveal that about 6 percent of infants are anemic, indicating a possible deficiency of iron in the diet (all anemias are not iron-deficiency related).

Diarrheal diseases and related sodium and potassium deficiencies are responsible for about two million infant deaths each year worldwide. Few of these deaths occur in the United States.

Causes and symptoms

Calcium and phosphorus deficiencies

Calcium and phosphorus are plentiful in foods, and dietary deficiencies are rare. Vitamin D deficiency impairs the absorption of dietary calcium and can provoke calcium deficiency (hypocalcemia) even when adequate calcium is consumed. Vitamin D deficiency can be found among young infants and the elderly who may be shielded from sunshine for prolonged periods. As women age, reductions in the hormone estrogen can affect the rate of calcium loss. Significant depletion of calcium stores can lead to osteoporosis. Deficiency of calcium or imbalances with phosphorus and magnesium can produce muscle cramping and digestive problems. Symptoms of calcium deficiency include joint pain , brittle nails, eczema, high cholesterol , insomnia, high blood pressure, nervousness, and tooth decay . Calcium deficiency can also contribute to cognitive problems (confusion, inattention, learning, and memory), convulsions, depression, and hyperactivity. Phosphorus deficiency can produce anxiety .

Sodium and potassium deficiencies

Deficiency or imbalance in sodium and potassium does not usually result from a lack of these minerals in the diet, but from imbalances in body fluids. This can be caused by excessive losses of body fluid (dehydration) from severe diarrhea or vomiting; laxative abuse; or during treatment of heart disease or high blood pressure (hypertension) with diuretic drugs, which are used to reduce fluid overload. Sodium and potassium imbalances can cause cardiac arrhythmias and shock (a reduced flow of blood and oxygen to tissues throughout the body). Although diarrheal fluids deplete a number of electrolytes (sodium, potassium, chloride, calcium, phosphorus, and magnesium), the main concern in avoiding shock is replacing sodium and water. Potassium deficiency alone can also affect nerve function.

Magnesium deficiency

Dietary magnesium deficiency is rare because the mineral is found in nearly all foods, but it can occur through poor diet or in malnutrition, or result from excessive losses due to severe diarrhea or vomiting. Symptoms of magnesium deficiency include faulty transmission of nerve and muscle impulses, irritability, nervousness, and tantrums . Confusion, poor digestion, rapid or irregular heartbeat (arrhythmia), and seizures can also result. Magnesium deficiency is associated with cardiac arrest, asthma , chronic fatigue syndrome, chronic pain, depression, insomnia, irritable bowel syndrome , and lung conditions.

Boron deficiency

Boron deficiency is rare, although reduced levels do occur with aging and with reduced levels of vitamin D. Because boron is involved in the absorption of calcium, the only symptom may be reduced levels of calcium or the inability to absorb supplemental calcium.

Chromium deficiency

Many Americans are deficient in dietary chromium, which can be associated with poor regulation of insulin and related imbalances in glucose (either diabetes or hypoglycemia ). Symptoms include fatigue, anxiety, poor protein metabolism, and glucose intolerance (as in diabetes). In adults, chromium deficiency can be a sign of coronary artery disease.

Copper deficiency

Copper is obtained through a balanced diet and deficiency is rare. Signs of copper deficiency may include anemia, diarrhea, weakness, poor respiratory function, baldness, skin sores, and increased lipid (fat) levels in the blood. Severe alterations in copper metabolism are seen in two rare genetic diseases: Wilson disease and Menkes' disease, which occur in about one in 100,000 births. Both diseases involve mutations in copper transport proteins, special channels that allow copper ions to pass through cell membranes. Menkes' disease, called the "kinky hair disease," results in tangled, grayish, steely, or kinky hair and chubby, rosy cheeks. Untreated Menkes' disease is associated with mental retardation and death before three years of age. Wilson disease involves decreases in copper in blood cells, the liver and brain; and increases in copper (copper toxicosis) in the cells of the intestines and kidneys. It results in degenerative changes in the brain, liver disease, and hemolytic anemia. Children older than five years who have any form of liver disease are often evaluated for serum and cellular copper levels to determine if Wilson disease is present.

Germanium deficiency

Germanium deficiency is rare; in fact, there is no established deficiency level.

Iodine deficiency

Iodine deficiency occurs when soil is iodine-poor and foods grown in the soil are correspondingly low in iodine. An iodine intake of 0.10–0.15 mg/day is considered to be nutritionally adequate. Iodine deficiency occurs when intake is below 0.05 mg/day. Goiter, an enlargement of the thyroid gland in the neck, results from iodine deficiency. Although goiter continues to be a problem in other parts of the world, it no longer occurs in the United States because of the fortification of foods with iodine. Iodine deficiency during pregnancy can result in cretinism in newborns, involving mental retardation and a large tongue.

Iron deficiency

Iron deficiency occurs most often because of poor iron intake and poor absorption. In children, iron deficiency is due to periods of dietary deficiency and heavy demands for iron during rapid growth. Human milk and cow's milk both contain low levels of iron; however, the iron in human milk is in a highly absorbable form. Infants are at risk for acquiring iron deficiency because their rapid rate of growth needs a corresponding increased supply of dietary iron, for use in making blood and muscles. Cow's milk formula is fortified with iron. Human milk is a better source of iron than cow's milk, since about half of the iron in human breast milk is absorbed by the infant's digestive tract. In contrast, only 10 percent of the iron in cow's milk is absorbed by the infant. Toddlers who drink excessive whole cow's milk are at risk for iron deficiency. Iron deficiency can also be caused by excess phosphorus in the diet, chronic intestinal bleeding, poor digestion and absorption, prolonged illness, ulcers, and the use of antacids. In women and teenage girls, blood loss through menstruation can result in iron deficiency. Symptoms of iron deficiency include anemia and resulting fatigue and weakness, especially during physical exertion. Fragile bones, brittle hair and nails, hair loss, spoon-shaped fingernails or ridges from the base of the nails to the ends, difficulty swallowing, nervousness, paleness, and lagging mental responses are also possible iron deficiency symptoms.

Manganese deficiency

Deficiency of manganese is very rare. Experimental studies of individuals fed a manganese deficient diet have revealed that the deficiency produces a scaly, red rash on the skin of the upper torso.

Selenium deficiency

Selenium deficiency may occur in premature infants who naturally tend to have about one-third the selenium levels of full-term infants. It is not known if these lower levels result in adverse consequences. Selenium deficiency occurs in regions of the world containing low-selenium soils, including parts of China, New Zealand, and Finland. In Keshan Province, China, a condition (Keshan disease) occurs that results in deterioration of regions of the heart and the development of fibers in these areas. Keshan disease, which may be fatal, is thought to result from a combination of selenium deficiency and a virus.

Zinc deficiency

Zinc deficiency can be caused by diarrhea, liver and kidney disease, alcoholism , diabetes, malabsorption, and overconsumption of fiber. Symptoms of zinc deficiency include acne , recurrent colds and flu, loss of senses of taste and smell, poor night vision, slow growth, lack of sexual maturation, lack of pubic hair, and small stature. Studies have shown that signs of zinc deficiency are detectable after two to five weeks of consuming a zinc-free diet. Signs include a rash on the face, groin, hands and feet, and diarrhea. Administering zinc will correct these symptoms.

When to call the doctor

Mineral deficiencies present with a wide variety of symptoms. Parents should observe children closely and report any unusual symptoms to the pediatrician, such as tiredness, weakness, depression or anxiety, irritability, nervousness, skin irritations, dehydration from vomiting or diarrhea, and slow growth or development of skills. Other than providing regular vitamin supplements and a balanced diet to prevent deficiencies, parents should not attempt to diagnose and treat deficiencies on their own.

Diagnosis

Individual minerals can be measured in blood serum, red blood cells, tissue cells, or urine, to estimate available levels and determine normal or abnormal status. Since each mineral performs strikingly different functions, tests to confirm deficiency are markedly different from each other. Testing can range from simple to extensive. Physicians will consider the possible consequences of each type of deficiency and evaluate the function of organ systems affected by the particular mineral.

In addition to determining serum calcium, phosphorus, and vitamin D levels, the diagnosis of calcium and phosphorus deficiency may involve taking x rays of the skeleton.

Diagnosing iron deficiency will require measuring iron levels and investigating anemia by performing blood tests such as a complete blood count (CBC) to determine the number of red blood cells, hemoglobin level, red cell volume, and cell maturity (morphology). A stair-stepping test may be used to evaluate stamina, but a blood test is required to diagnose iron deficiency.

Diagnosing low levels or imbalances of the electrolytes sodium, potassium, calcium, magnesium, or phosphate involves measuring the serum levels of each. Measurement determines the circulating blood level at the time blood was drawn. Laboratory values of sodium and potassium, which are present within cells and in the fluid between cells, can change rapidly depending on the individual's overall condition. They may be measured repeatedly to determine a trend and to monitor correction of the deficiency or imbalance after diagnosis.

Normal serum magnesium levels are 1.2–2.0 mE/l, while levels in deficiency (hypomagnesemia) are below 0.8 mE/l. Because calcium and magnesium must remain balanced, magnesium levels below 0.5 mE/l can provoke a decline in serum calcium levels. Hypomagnesemia can also result in low serum potassium. Symptoms of hypomagnesemia, such as twitching and convulsions, may actually result from the hypocalcemia. Other symptoms, such as cardiac arrhythmias, actually occur because of low potassium. All three minerals will be measured.

Iodine deficiency is diagnosed by measuring the concentration of iodine in urine. A urinary level greater than 0.05 mg iodine per gram of creatinine (another metabolite excreted in urine) indicates adequate iodine status. Levels under 0.025 mg iodine/gram creatinine indicate serious risk. The doctor may also examine the neck with the eyes and hands to see if a goiter is present.

Urinary zinc levels will differ between normal dietary intake (16 mg per day) and low-zinc diets (0.3 mg per day); normal urinary zinc is about 0.45 mg per day while low-zinc urinary levels are about 0.150 mg per day. Plasma zinc levels tend to be maintained during a dietary deficiency in zinc. Plasma and urinary zinc levels can be influenced by a variety of factors, and for this reason cannot provide a clear picture of zinc status.

Selenium can be measured in plasma or red blood cells and compared to normal values. The activity of an enzyme (glutathione peroxidase) in platelets (small blood cells essential in blood clotting) may be evaluated to assess selenium status.

Treatment

Most mineral deficiencies can be successfully treated through diet or supplementation, except when caused by disease, which requires treatment of the disease.

Treating fluid imbalances and related deficiencies in sodium, potassium, calcium, and phosphate usually requires intravenous (IV) infusion of the deficient mineral in fluid over a period of time. Sudden changes in sodium and potassium levels can be just as dangerous as low levels; caution is used to restore balance gradually. Children may be given oral pediatric preparations to gradually restore fluids and minerals.

Iron deficiency requires oral supplementation or injectable iron. Vitamin C helps to assimilate iron.

Iodine deficiency is easily treated and prevented by consuming foods fortified with iodine, such as table salt. Goiter is reversible with treatment but cretinism is not.

A magnesium-rich diet will correct magnesium deficiency. If deficiency is due to prolonged depletion, treatment may include injections of magnesium sulfate; if severe enough to provoke convulsions, intravenous infusions may be given.

Selenium deficiency can be treated by supplementation. Children can be given supplements containing 1.0 mg sodium selenite.

Zinc and copper deficiencies are rare and can be treated with supplementation.

Prognosis

The prognosis for mineral deficiencies depends on the extent of deficiency at diagnosis, the degree of effects or symptoms, and the overall health of the individual. Correction through diet or supplements usually produces good results. Symptoms may sometimes be relieved promptly with supplementation. Some deficiencies produce permanent effects of varying severity.

In iodine deficiency, the prognosis for treating goiter is excellent. Sodium and potassium deficiencies or imbalances can be corrected if diagnosed and treated promptly, but can be life-threatening if untreated. Anemia and other effects of iron deficiency are not usually life-threatening and can be corrected with supplementation. "Silent" or undiagnosed calcium loss may result in osteoporosis, which may produce disability or complications by the time it is diagnosed.

Alternative treatment

Sea vegetables (sea weeds such as dulse, kelp, wakambe, and hijiki) are an excellent source of minerals obtained from the ocean. They can be used to make soup stock, added to stews and casseroles, or served with vegetables. Herbs are a valuable source of minerals as well. For example, calcium is found in alfalfa, burdock root, chamomile, dandelion, flaxseed, paprika, raspberry leaves, rose hips, and other herbs. Iron is found in the same herbs as calcium, and in the Chinese herb dong quai (angelica), as well as other herbs.

Prevention

Ensuring an adequate intake of essential nutrients through a balanced diet and supplements is the best way to prevent mineral deficiencies. The Required Dietary Allowances (RDA) guidelines can help ensure that minerals are being obtained. Safe amounts of certain minerals are often included in multivitamins. Because excess mineral levels can also cause health problems, taking excessive amounts of any mineral supplement is not advised unless a deficiency is diagnosed. When mineral deficiency is the result of disease, medical attention, other than preventive measures, is required.

Nutritional concerns

A balanced diet includes fresh vegetables and fruits, legumes, whole grains (cereal, bread, rice, pasta, and other grains), eggs, dairy products, fish, fowl, and lean meat as preferred. A diet high in refined foods, prepared foods, sugars, and fats will not provide sufficient quantities of essential minerals. Water delivers nutrients throughout the body; it is essential to drink enough clean water daily to maintain fluid balance and distribute nutrients.

Essential mineral nutrients are found in a variety of sources, as in these examples:

KEY TERMS

Electrolytes —Salts and minerals that produce electrically charged particles (ions) in body fluids. Common human electrolytes are sodium chloride, potassium, calcium, and sodium bicarbonate. Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.

Nutrient —Substances in food that supply the body with the elements needed for metabolism. Examples of nutrients are vitamins, minerals, carbohydrates, fats, and proteins.

Osteoporosis —Literally meaning "porous bones," this condition occurs when bones lose an excessive amount of their protein and mineral content, particularly calcium. Over time, bone mass and strength are reduced leading to increased risk of fractures.

Recommended Dietary Allowance (RDA) —The Recommended Dietary Allowances (RDAs) are quantities of nutrients in the diet that are required to maintain good health in people. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences, and may be revised every few years. A separate RDA value exists for each nutrient. The RDA values refer to the amount of nutrient expected to maintain good health in people. The actual amounts of each nutrient required to maintain good health in specific individuals differ from person to person.

• Boron is abundant in apples, pears, grapes, leafy greens, carrots, whole grains, and nuts.
• Primary calcium sources are dairy foods, eggs, fish, and green leafy vegetables. Other calcium-rich foods are figs, broccoli, cabbage, oats, almonds and filberts, yogurt, and blackstrap molasses. Spinach and Swiss chard bind calcium in the digestive tract and are not a ready source.
• Chromium is found in brown rice and other whole grains, cheeses, meats, dried beans, corn, eggs, mushrooms, and potatoes.
• Copper is found in nuts, mushrooms, broccoli, garlic, lentils, salmon, and green vegetables. It is also found in plumbing and cooking pots, which may leach into food and water.
• Germanium occurs primarily in garlic, shiitake mushrooms, and onions.
• Iron can be provided by eating green leafy vegetables, raisins, meat, eggs, liver, fish and fowl, nuts, and whole grains. It can also be obtained by cooking in iron skillets.
• Magnesium is found in most foods, primarily animal and fish sources.
• Potassium food sources include dairy foods, fish, fresh and dried fruits, beans and peas, meats, fish and fowl, and whole grains.
• Zinc sources include brewer's yeast, eggs, fish, meats, beans, mushrooms, nuts and seeds, and whole grains.

Parental concerns

Good nutrition is a concern of all parents. In the United States, it is relatively easy to provide a balanced diet with essential nutrients if a wide variety of whole foods are prepared for family meals and snacks, while avoiding refined and prepared foods high in fats and sugars. RDA guidelines and public health resources can help assure parents that they can prevent dietary deficiencies in their young children and teens.

Resources

BOOKS

Balch, James, and Phyllis Balch.Prescription for Nutritional Healing, 3rd ed. New York: Avery Publishing Group, 2002.

Brody, Tom. Nutritional Biochemistry. San Diego: Academic Press, 1998.

ORGANIZATIONS

American Society for Nutritional Sciences (ASNS). 9650 Rockville Pike, Suite 4500, Bethesda, MD 20814. (301) 634-7050. Web site: <www.nutrition.org>.

WEB SITES

Food and Nutrition Information (FNIC). [cited October 9, 2004]. Available online at: <www.nal.usda.gov/fnic/>.

L. Lee Culvert Tom Brody, Ph.D.

Mineral deficiency

Definition

Mineral deficiency describes a condition in which 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 to an impairment in a function dependent on the mineral. In other cases, an abnormally low mineral concentration signifies a lower level than that found in a specific healthy population.

Mineral nutrients are the inorganic elements or inorganic molecules required for life. As far as human nutrition is concerned, the inorganic nutrients include water, sodium, potassium, chloride, calcium , phosphate, sulfate, magnesium, iron , copper , zinc , manganese, iodine, selenium, and molybdenum. Some of the inorganic nutrients, such as water, do not occur as single atoms, but occur as molecules. Other inorganic nutrients that are molecules include phosphate, sulfate, and selenite. Phosphate contains an atom of phosphorus . Sulfate contains an atom of sulfur. Humans do not need to eat sulfate, since the body can acquire all the sulfate it needs from protein. Selenium occurs in foods as selenite and selenate.

The mineral content of the body can 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 with the eyes and hands. In the case of iron deficiency, the diagnosis may include the performance of a stair-stepping test by the patient. Since all the minerals serve strikingly different functions in the body, the tests for the corresponding deficiency are markedly different from each other.

Description

Laboratory studies with animals have revealed that severe deficiencies in any one of the inorganic nutrients can result in very specific symptoms, and finally in death, due to the failure of functions associated with that nutrient. In humans, deficiency in one nutrient may occur less often than deficiency in several nutrients. A patient suffering from malnutrition is deficient in a variety of nutrients. In the United States, malnutrition is most often found among severe alcoholics. In part, this is because the alcohol consumption may supply half of the energy requirement, resulting in a mineral and vitamin intake of half the expected level. Deficiencies in one nutrient do occur, for example, in human populations living in iodine-poor regions of the world, and in iron deficient persons who lose excess iron by bleeding.

Inorganic nutrients have a great 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 fluid and electrolyte losses due to severe diarrhea and other causes. Iodine deficiency is a global public health problem. 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 only use of iodine in the body is for making thyroid hormone. However, since thyroid hormone has a variety of roles in development of the embryo, iodine deficiency during pregnancy results in a number of birth defects.

Calcium from the diet is absorbed in the gastrointestinal tract while the excess is excreted in the urine. A minimum of 500–1000 mg of calcium is required daily in order to maintain a normal calcium concentration. Normally, the body transfers calcium to the blood from the bones to maintain calcium homeostasis. If calcium intake falls short of requirement, too much calcium will be mobilized from the bones, weakening the bones and contributing to osteoporosis .

Dietary phosphate deficiency is rare because phosphate is plentiful in plant and animal foods, but also because phosphate is efficiently absorbed from the diet 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 is uncommon, but when it occurs it 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 is found primarily in impoverished populations in the Middle East, who rely on unleavened whole wheat bread as a major food source. Copper deficiency is 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. Low-selenium soils can produce foods that are also low in selenium. Premature infants may also be at risk for selenium deficiency.

Causes and symptoms

Sodium deficiency

Sodium deficiency (hyponatremia) and water imbalances (dehydration ) are the most serious and widespread deficiencies in the world. These electrolyte deficiencies tend to arise from excessive 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, where they result from 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 . Shock nearly always occurs when dehydration is severe enough to produce a 10% reduction in body weight. Shock, which is defined as inadequate supply of blood to the various tissues of the body, results in a lack of oxygen to all the cells of the body. Although diarrheal fluids contain a number of electrolytes, the main concern in avoiding shock is the replacement of sodium and water.

Sodium deficiency also frequently results during treatment with drugs called diuretics. Diuretics cause a loss of sodium from the body. These drugs are used to treat high blood pressure (hypertension ), where the resulting decline in blood pressure reduces the risk for cardiovascular disease. However, diuretics can lead to sodium deficiency, resulting in low plasma sodium levels. Hyponatremia occurs in approximately 1% of all hospital admissions and is especially problematic in the elderly.

Potassium deficiency

Potassium plays a major part in cell metabolism and in nerve and muscle cell function. Most of the body's potassium is located in the cells. Too high or low concentrations of blood potassium can have serious effects such as an abnormal heart rhythm or cardiac arrest. Like other electrolytes, potassium balance is regulated through gastrointestinal tract absorption of food, while excretion is controlled by the kidney.

A low potassium blood level is referred to as hypokalemia. Hypokalemia is common in the elderly. Common causes include decreased intake of potassium during acute illness, nausea and vomiting, and treatment with diuretics. Since several foods contain potassium, hypokalemia is not typically due to a low intake. It is usually due to malfunction of the kidneys or abnormal loss through the gastrointestinal tract. People with heart disease have to be especially cautious regarding hypokalemia (particularly when taking digoxin), because they are prone to developing abnormal rhythms. A side effect of some diuretics is excessive loss of potassium, therefore, hypokalemia may result.

High sources of potassium are:

• bananas
• melons
• tomatoes
• oranges
• potatoes and sweet potatoes
• green leafy vegetables such as spinach, turnip greens, collard greens, kale, etc.
• most peas and beans
• potassium supplements
• salt substitutes (potassium chloride)

Calcium and phosphate deficiency

Calcium and phosphate are closely related nutrients. About 99% of the calcium and 85% of the phosphate in the body occur in the skeleton, where they exist as crystals of solid calcium phosphate. Conditions such as growth, pregnancy, and lactation are associated with increased phosphate requirements.

The body's calcium reserves are predominantly stored in bones although the blood and cells also contain calcium. Calcium is necessary for proper functioning in many areas of the body including nerve conduction, muscle contraction , and enzyme functions. Like other electrolytes, calcium levels are controlled both in blood and cells. A low calcium blood level is referred to as hypocalcemia. Hypocalcemia can result from a number of problems. The most common reason is an inability to mobilize calcium from the bones or a chronic loss of calcium in the urine.

Other causes of hypocalcemia include:

• low blood albumin concentration
• hypoparathyroidism
• vitamin D deficiency
• renal failure
• magnesium depletion
• acute pancreatitis
• hypoproteinemia (low blood protein)
• septic shock
• hyperphosphatemia (high blood phosphate levels)
• drugs such as those used to treat hypercalcemia or anticonvulsants
• excessive secretion of calcitonin

An abnormally low blood calcium concentration may not produce any symptoms. However, over time, the lack of calcium in the blood can affect brain function, causing neurologic symptoms such as memory loss, depression, confusion, delirium, and hallucinations. Once calcium levels return to normal, these symptoms are reversible. Very severe cases of hypocalcemia can lead to seizures, tetany, and muscle spasms in the throat, affecting breathing.

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 hence vitamin D deficiency in growing infants and children can result in calcium deficiency. The body can produce Vitamin D with sun exposure. Vitamin D deficiency can be found among young infants, the elderly, and others who may be shielded from sunshine for prolonged periods of time. Vitamin D deficiency impairs the absorption of calcium from the diet, and in this way can provoke calcium deficiency even when the diet contains adequate calcium.

Both calcium and phosphate occur in a great variety of foods, but many men, and women in particular, consume less than the required amount of calcium daily. Men over 65 years, postmenopausal women, and women who are lactating tend to be in negative calcium balance, and thus calcium is drawn from the bones to maintain calcium homeostatis. Milk, eggs, and green, leafy vegetables are rich in calcium and phosphate. Whole cow milk, for example, contains about 1.2 g calcium and 0.95 g phosphorus per 2.2 lbs (1 kg) of food. Broccoli contains1.0 g calcium and 0.67 g phosphorus per 2.2 lbs (1 kg) of food. Meat, poultry, and fish are also high in phosphorus (phosphate).

Iodine deficiency

Iodine deficiency tends to occur in regions of the world where the soil is poor in iodine. Where soil used in agriculture is low in iodine, the foods grown in the soil will also be iodine poor. An iodine intake of 0.10–0.15 mg/day is considered to be nutritionally adequate, while iodine deficiency occurs at below 0.05 mg/day. 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 foods with iodine. Iodine deficiency during pregnancy results in cretinism in the newborn. Cretinism involves mental retardation, a large tongue, and sometimes deafness, muteness, and lameness.

Iron deficiency

Iron deficiency occurs due to periods of dietary deficiency, rapid growth, and excessive loss of the body's iron. Human milk and cow milk both contain low levels of iron. Infants are at risk for iron deficiency because their rapid rate of growth needs a corresponding increased supply 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 deficiency are generally limited to anemia, and the resulting tiredness, weakness, and a reduced ability to perform physical work.

Magnesium deficiency

Magnesium influences the function of many enzymes. Dietary intake is essential to maintain normal levels. The body's magnesium stores are predominately found in bone with little appearing in the blood. Excess is excreted in the urine or stool.

Magnesium deficiency results in hypomagnesemia, which is defined as serum magnesium levels below 0.8 mmol/L. Normal blood serum magnesium levels are1.2–2.0 mmol/L. Some of the symptoms of hypomagnesemia, which include twitching and convulsions, actually result from hypocalcemia. Other symptoms of hypomagnesemia, such as cardiac arrhythmias, result from low potassium levels. Metabolic and nutritional disorders are usually the culprit of hypomagnesemia, most often when intake of magnesium is decreased during starvation or intestinal malabsorption compounded with greater kidney excretion. Magnesium levels below 0.5 mmol/L provoke a decline in serum calcium levels. Hypomagnesemia can also result in low serum potassium.

Zinc deficiency

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 energy intake in these areas. This diet, which does not contain meat, does contain zinc, but it also contains phytic acid at a level of about 3 g/day. The phytic acid, which naturally occurs in wheat, inhibits zinc absorption. The yeast used to leaven bread produces enzymes that inactivate the phytic acid. Unleavened bread does not contain yeast, and therefore, contains intact phytic acid. The symptoms of zinc deficiency include lack of sexual maturation, lack of pubic hair, and small stature. The amount of phytic acid in a typical American diet cannot provoke zinc deficiency.

Zinc deficiency is relatively uncommon in healthy adults in the United States, but often occurs in adults with alcoholism or intestinal malabsorption problems. Zinc levels also may be problematic in the elderly, pregnant women, diabetics, AIDS patients, and those with chronic infections and/or trauma. Low plasma zinc has been found in patients with alcoholic cirrhosis, Crohn's disease , and celiac disease. Experimental studies with humans have shown that the signs of zinc deficiency are detectable after two to five weeks of consumption of the zinc-free diet. The signs include a rash and diarrhea. The rash occurs on the face, groin, hands, and feet. These symptoms can easily be reversed by administering zinc. Absorption of zinc is largely dependent on the presence or absence of other foods that affect zinc absorption. Meats, liver , eggs, and seafoods are good choices of zinc because these foods do not contain many other components which interfere with zinc absorption. An emerging concern is that increased calcium intake can interfere with zinc absorption or retention. Hence, there is some interest in the question of whether persons taking calcium to prevent osteoporosis should also take zinc supplements.

Copper deficiency

Copper deficiency is relatively uncommon but severe alterations in copper metabolism occur in two genetic diseases, Wilson's disease and Menkes' disease. Both of these diseases are rare. Menkes'disease occurs in about one in 50,000 to 100,000 births while Wilson's disease occurs in approximately one in 200,000 births in the United States. Both diseases involve mutations in copper transport proteins , that is, in special channels that allow the passage of copper ions through cell membranes . Menkes' disease is a genetic disease involving mental retardation and death before the age of three years. The disease also results in steely or kinky hair. The hair is tangled, grayish, and easily broken. Menkes' disease involves a decrease in copper levels in the serum, liver, and brain, and increases in copper in the cells of the intestines and kidney.

The richest sources of copper are shellfish, nuts, seeds, cocoa powder, liver, organ meats, legumes, and the germ and bran portions of grains.

Selenium deficiency

Selenium deficiency may occur in premature infants, since this population naturally tends to have low levels of plasma selenium. Full term infants have plasma selenium levels of about 0.001–0.002 mmol/L, while premature infants may have levels about one third this amount. Whether these lower levels result in adverse consequences is not clear. Total parental nutrition often leads to selenium deficiency if it is not administered in the fluids. 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. Keshan disease, which may be fatal, is thought to result from a combination of selenium deficiency and a virus.

The richest sources of selenium are organ meats and seafood. In addition, muscle meats, cereals and grains, dairy products, and fruits and vegetables provide good sources of selenium.

Other ultratrace mineral deficiencies

Manganese deficiency is very rare. Experimental studies with humans fed a manganese deficient diet have revealed that the deficiency produces a scaly, red rash on the skin of the upper torso. The importance of manganese in human nutrition still needs to be established. It is thought that the possibility in becoming manganese deficient is increased in alcohol abusers. Molybdenum deficiency has probably never occurred, but indirect evidence suggests that if molybdenum deficiency could occur, it would result in mental retardation and death

There is some evidence that other inorganic nutrients, such as chromium and boron, play a part in human health, but their role is not well established. Chromium has a function related to insulin and thus influences carbohydrate, lipid, and protein metabolism. Boron is believed to affect macromineral metabolism in humans. Fluoride has been proven to increase the strength of bones and teeth, but there is little or no reason to believe that is needed for human life.

Diagnosis

The diagnosis of deficiencies in water, sodium, potassium, iron, calcium, and phosphate involve chemical testing of the blood plasma, urine, and red blood cells.

KEY TERMS

Dehydration —A deficit of body water that results when the output of water exceeds intake.

Diuretic —An agent or drug that eliminates excessive water in the body by increasing the flow of urine.

Electrolyte —A substance such as an acid, bases, or salt. An electrolyte's water solution will conduct an electric current and ionizes. Calcium, potassium, magnesium, and sodium are electrolytes.

Homeostatis —An organism's regulation of body processes to maintain internal equilibrium in temperature and fluid content.

Recommended Dietary Allowance —The Recommended Dietary Allowances (RDAs) are quantities of nutrients that are required each day to maintain human health. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences and may be revised every few years. A separate RDA value exists for each nutrient. In 2001, the RDA will be replaced by the Dietary Reference Intakes (DRI) and will apply to Americans and Canadians.

Hypocalcemia is usually first discovered during routine blood tests because often there are no symptoms evident.

Iodine deficiency can be diagnosed by measuring the concentration of iodine in the urine. A urinary level greater than 0.05 mg iodine per gram creatinine means adequate iodine status. Levels under 0.025 mg iodine/g creatinine indicate a serious risk.

There is no reliable test for zinc deficiency. When humans eat diets containing normal levels of zinc (16 mg/day), the level of urinary zinc is about 0.45 mg/day, while humans consuming low-zinc diets (0.3 mg/day) may have urinary levels of about 0.150 mg/day. Plasma zinc levels tend to be maintained during a dietary deficiency in zinc. Plasma and urinary zinc levels can be influenced by a variety of factors, and for this reason cannot provide a clear picture of zinc status.

Selenium deficiency may be diagnosed by measuring the selenium in plasma (70 ng/mL) or red blood cells (90 ng/mL), where the normal values are indicated. There is also some interest in measuring the activity of an enzyme in blood platelets, in order to assess selenium status. This enzyme is glutathione peroxidase. Platelets are small cells of the bloodstream which are used mainly to allow the clotting of blood after an injury.

Treatment

The treatment of deficiencies in sodium, potassium, calcium, phosphate, and iron often involves intravenous injections of the deficient mineral. Potassium, however, usually can be replaced relatively easily by eating foods rich in potassium or by taking potassium salts (potassium chloride) orally.

Iodine deficiency can be easily prevented and treated by fortifying foods with iodine. Table salt is fortified with 100 mg potassium iodide per kg sodium chloride. Goiter was once common in the United States in areas from Washington State to the Great Lakes region, but this problem has been eliminated by iodized salt. Public health programs in impoverished countries have administered injections of synthetic oils containing iodine. Goiter is reversible, but cretinism is not.

Magnesium deficiency can be treated with a magnesium rich diet. If magnesium deficiency is due to a prolonged period of depletion, treatment may include injections of magnesium sulfate (2.0 mL of 50% MgSO₄). Where magnesium deficiency is severe enough to provoke convulsions, magnesium needs to be administered by injections or infusions. For infusion, 500 mL of a 1% solution (1 gram/100 mL) of magnesium sulfate is gradually introduced into a vein over the course of about five hours. When hypomagnesemia occurs along with hypocalcemia, the magnesium must be replaced before successful treatment of the calcium disorder.

Zinc deficiency and copper deficiency are quite uncommon, but when they are detected or suspected, they can be treated by consuming zinc or copper, on a daily basis, at levels defined by the RDA.

Selenium deficiency in adults can be treated by eating 100 mg selenium per day for a week, where the selenium is supplied as selenomethionine. The incidence of Keshan disease in China has been reduced by supplementing children with 1.0 mg sodium selenite per week.

Prognosis

In iodine deficiency, the prognosis for treating goiter is excellent, however cretinism cannot be reversed. The effects of iron deficiency are not life-threatening and can be easily treated. The prognosis for treating magnesium deficiency is excellent. The symptoms may be relieved promptly or, at most, within two days of starting treatment. In cases of zinc deficiency in Iran and other parts of the Middle East, supplementation of affected young adults with zinc has been found to provoke the growth of pubic hair and enlargement of genitalia to a normal size within a few months.

Health care team roles

Mineral deficiencies are normally diagnosed and treated by physicians. Dieteticians may be employed in efforts of patient education . For example, the dietetician may counsel a patient about a healthy diet to prevent further deficiencies, or be involved in community programs to educate the public at large.

Prevention

In the healthy population, all mineral deficiencies can be prevented by the consumption of inorganic nutrients at levels defined by the Recommended Dietary Allowances (RDA) or Dietary Reference Intakes (DRI). Where a balanced diet is not available, government programs for treating individuals, or for fortifying the food supply, may be used. Government sponsored programs for the prevention of iron deficiency and iodine deficiency are widespread throughout the world. Selenium treatment programs have been used in parts of the world where selenium deficiency exists. Attention to potassium status, and to the prevention of potassium deficiency, is an issue mainly in patients taking diuretic drugs. In many cases of mineral deficiency, the deficiency occurs because of disease, and individual medical attention, rather than preventative measures, is used. Calcium supplements are widely used with the hope of preventing osteoporosis. The prevention of deficiencies in magnesium, copper, manganese, or molybdenum are not major health issues in the United States. Ensuring an adequate intake of these minerals, by eating a balanced diet or by taking mineral supplements, is the best way to prevent deficiencies.

Resources

BOOKS

Brody, Tom. Nutritional Biochemistry. San Diego: Academic Press, 1998.

Institute of Medicine, ed. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington: National Academy Press, 1999.

Larson-Duyff, Roberta. The American Dietetic Association's Complete Food & Nutrition Guide. New York: John Wiley & Sons, 1998.

Murray, Michael T. Encyclopedia of Nutritional Supplements: The Essential Guide for Improving Your Health Naturally. Rocklin, CA: Prima Publishing, 2001.

National Academy Press Food and Nutrition Board Recommended Dietary Allowances, 10th edition. Washington: National Academy Press, 1989.

PERIODICALS

Foote, J. A., A. R. Giuliano, and R. B. Harris. "Older adults need guidance to meet nutritional recommendations." Journal of the American College of Nutrition 19, no. 5 (Oct. 2000): 628-40.

Fryer, M. J. "Selenium and human health." Lancet 356, no. 9233 (Sept. 9, 2000): 943.

Lonnerdal, B. "Dietary factors influencing zinc absorption." Journal of Nutrition 130, no. 5S Suppl (May 2000): 1378S-83S.

Rayman, M. P. "The importance of selenium to human health." Lancet 356, no. 9225 (Jul 15, 2000): 233-41.

ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd. Chicago, IL 60606-6995. (312) 899-0040. <http://www.eatright.org/>.

Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 20705-2351. (301) 504-5719. Fax (301) 504-6409. <http://www.nal.usda.gov/fnic/>. [email protected].

OTHER

Food and Nutrition Professionals Network. <http://nutrition.cos.com/>.

Crystal Heather Kaczkowski, MSc.

Mineral Deficiency

Definition

Mineral deficiency describes a condition in which 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 to an impairment in a function dependent on the mineral. In other cases, an abnormally low mineral concentration signifies a lower level than that found in a specific healthy population.

Mineral nutrients are the inorganic elements or inorganic molecules required for life. As far as human nutrition is concerned, the inorganic nutrients include water, sodium, potassium, chloride, calcium, phosphate, sulfate, magnesium, iron, copper, zinc, manganese, iodine, selenium, and molybdenum. Some of the inorganic nutrients, such as water, do not occur as single atoms, but occur as molecules. Other inorganic nutrients that are molecules include phosphate, sulfate, and selenite. Phosphate contains an atom of phosphorus. Sulfate contains an atom of sulfur. Humans do not need to eat sulfate, since the body can acquire all the sulfate it needs from protein. Selenium occurs in foods as selenite and selenate.

The mineral content of the body can 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 with the eyes and hands. In the case of iron deficiency, the diagnosis may include the performance of a stair-stepping test by the patient. Since all the minerals serve strikingly different functions in the body, the tests for the corresponding deficiency are markedly different from each other.

Description

Laboratory studies with animals have revealed that severe deficiencies in any one of the inorganic nutrients can result in very specific symptoms, and finally in death, due to the failure of functions associated with that nutrient. In humans, deficiency in one nutrient may occur less often than deficiency in several nutrients. A patient suffering from malnutrition is deficient in a variety of nutrients. In the United States, malnutrition is most often found among severe alcoholics. In part, this is because the alcohol consumption may supply half of the energy requirement, resulting in a mineral and vitamin intake of half the expected level. Deficiencies in one nutrient do occur, for example, in human populations living in iodinepoor regions of the world, and in iron deficient persons who lose excess iron by bleeding.

Inorganic nutrients have a great 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 fluid and electrolyte losses due to severe diarrhea and other causes. Iodine deficiency is a global public health problem. 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 only use of iodine in the body is for making thyroid hormone. However, since thyroid hormone has a variety of roles in development of the embryo, iodine deficiency during pregnancy results in a number of birth defects.

Calcium from the diet is absorbed in the gastrointestinal tract while the excess is excreted in the urine. A minimum of 500-1000 mg of calcium is required daily in order to maintain a normal calcium concentration. Normally, the body transfers calcium to the blood from the bones to maintain calcium homeostasis. If calcium intake falls short of requirement, too much calcium will be mobilized from the bones, weakening the bones and contributing to osteoporosis.

Dietary phosphate deficiency is rare because phosphate is plentiful in plant and animal foods, but also because phosphate is efficiently absorbed from the diet 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 is uncommon, but when it occurs it 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 is found primarily in impoverished populations in the Middle East, who rely on unleavened whole wheat bread as a major food source. Copper deficiency is 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. Low-selenium soils can produce foods that are also low in selenium. Premature infants may also be at risk for selenium deficiency.

Causes and symptoms

Sodium deficiency

Sodium deficiency (hyponatremia) and water imbalances (dehydration) are the most serious and widespread deficiencies in the world. These electrolyte deficiencies tend to arise from excessive 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, where they result from 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. Shock nearly always occurs when dehydration is severe enough to produce a 10% reduction in body weight. Shock, which is defined as inadequate supply of blood to the various tissues of the body, results in a lack of oxygen to all the cells of the body. Although diarrheal fluids contain a number of electrolytes, the main concern in avoiding shock is the replacement of sodium and water.

Sodium deficiency also frequently results during treatment with drugs called diuretics. Diuretics cause a loss of sodium from the body. These drugs are used to treat high blood pressure (hypertension), where the resulting decline in blood pressure reduces the risk for cardiovascular disease. However, diuretics can lead to sodium deficiency, resulting in low plasma sodium levels. Hyponatremia occurs in approximately 1% of all hospital admissions and is especially problematic in the elderly.

Potassium deficiency

Potassium plays a major part in cell metabolism and in nerve and muscle cell function. Most of the body's potassium is located in the cells. Too high or low concentrations of blood potassium can have serious effects such as an abnormal heart rhythm or cardiac arrest. Like other electrolytes, potassium balance is regulated through gastrointestinal tract absorption of food, while excretion is controlled by the kidney.

A low potassium blood level is referred to as hypokalemia. Hypokalemia is common in the elderly. Common causes include decreased intake of potassium during acute illness, nausea and vomiting, and treatment with diuretics. Since several foods contain potassium, hypokalemia is not typically due to a low intake. It is usually due to malfunction of the kidneys or abnormal loss through the gastrointestinal tract. People with heart disease have to be especially cautious regarding hypokalemia (particularly when taking digoxin), because they are prone to developing abnormal rhythms. A side effect of some diuretics is excessive loss of potassium, therefore, hypokalemia may result.

High sources of potassium are:

• bananas
• melons
• tomatoes
• oranges
• potatoes and sweet potatoes
• green leafy vegetables such as spinach, turnip greens, collard greens, kale, etc.
• most peas and beans
• potassium supplements
• salt substitutes (potassium chloride)

Calcium and phosphate deficiency

Calcium and phosphate are closely related nutrients. About 99% of the calcium and 85% of the phosphate in the body occur in the skeleton, where they exist as crystals of solid calcium phosphate. Conditions such as growth, pregnancy, and lactation are associated with increased phosphate requirements.

The body's calcium reserves are predominantly stored in bones although the blood and cells also contain calcium. Calcium is necessary for proper functioning in many areas of the body including nerve conduction, muscle contraction, and enzyme functions. Like other electrolytes, calcium levels are controlled both in blood and cells. A low calcium blood level is referred to as hypocalcemia. Hypocalcemia can result from a number of problems. The most common reason is an inability to mobilize calcium from the bones or a chronic loss of calcium in the urine.

Other causes of hypocalcemia include:

• low blood albumin concentration
• hypoparathyroidism
• vitamin D deficiency
• renal failure
• magnesium depletion
• acute pancreatitis
• hypoproteinemia (low blood protein)
• septic shock
• hyperphosphatemia (high blood phosphate levels)
• drugs such as those used to treat hypercalcemia or anticonvulsants
• excessive secretion of calcitonin

An abnormally low blood calcium concentration may not produce any symptoms. However, over time, the lack of calcium in the blood can affect brain function, causing neurologic symptoms such as memory loss, depression, confusion, delirium, and hallucinations. Once calcium levels return to normal, these symptoms are reversible. Very severe cases of hypocalcemia can lead to seizures, tetany, and muscle spasms in the throat, affecting breathing.

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 hence, vitamin D deficiency in growing infants and children can result in calcium deficiency. The body can produce Vitamin D with sun exposure. Vitamin D deficiency can be found among young infants, the elderly, and others who may be shielded from sunshine for prolonged periods of time. Vitamin D deficiency impairs the absorption of calcium from the diet, and in this way can provoke calcium deficiency even when the diet contains adequate calcium.

Both calcium and phosphate occur in a great variety of foods, but many men, and women in particular, consume less than the required amount of calcium daily. Men over 65 years, postmenopausal women, and women who are lactating tend to be in negative calcium balance, and thus calcium is drawn from the bones to maintain calcium homeostatis. Milk, eggs, and green, leafy vegetables are rich in calcium and phosphate. Whole cow milk, for example, contains about 1.2 g calcium and 0.95 g phosphorus per 2.2 lbs (1 kg) of food. Broccoli contains 1.0 g calcium and 0.67 g phosphorus per 2.2 lbs (1 kg) of food. Meat, poultry, and fish are also high in phosphorus (phosphate).

Iodine deficiency

Iodine deficiency tends to occur in regions of the world where the soil is poor in iodine. Where soil used in agriculture is low in iodine, the foods grown in the soil will also be iodine poor. An iodine intake of 0.10-0.15 mg/day is considered to be nutritionally adequate, while iodine deficiency occurs at below 0.05 mg/day. 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 foods with iodine. Iodine deficiency during pregnancy results in cretinism in the newborn. Cretinism involves mental retardation, a large tongue, and sometimes deafness, muteness, and lameness.

Iron deficiency

Iron deficiency occurs due to periods of dietary deficiency, rapid growth, and excessive loss of the body's iron. Human milk and cow milk both contain low levels of iron. Infants are at risk for iron deficiency because their rapid rate of growth needs a corresponding increased supply 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 deficiency are generally limited to anemia, and the resulting tiredness, weakness, and a reduced ability to perform physical work.

Magnesium deficiency

Magnesium influences the function of many enzymes. Dietary intake is essential to maintain normal levels. The body's magnesium stores are predominately found in bone with little appearing in the blood. Excess is excreted in the urine or stool.

Magnesium deficiency results in hypomagnesemia, which is defined as serum magnesium levels below 0.8 mmol/L. Normal blood serum magnesium levels are 1.2-2.0 mmol/L. Some of the symptoms of hypomagnesemia, which include twitching and convulsions, actually result from hypocalcemia. Other symptoms of hypomagnesemia, such as cardiac arrhythmias, result from low potassium levels. Metabolic and nutritional disorders are usually the culprit of hypomagnesemia, most often when intake of magnesium is decreased during starvation or intestinal malabsorption compounded with greater kidney excretion. Magnesium levels below 0.5 mmol/L provoke a decline in serum calcium levels. Hypomagnesemia can also result in low serum potassium.

Zinc deficiency

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 energy intake in these areas. This diet, which does not contain meat, does contain zinc, but it also contains phytic acid at a level of about 3 g/day. The phytic acid, which naturally occurs in wheat, inhibits zinc absorption. The yeast used to leaven bread produces enzymes that inactivate the phytic acid. Unleavened bread does not contain yeast, and therefore, contains intact phytic acid. The symptoms of zinc deficiency include lack of sexual maturation, lack of pubic hair, and small stature. The amount of phytic acid in a typical American diet cannot provoke zinc deficiency.

Zinc deficiency is relatively uncommon in healthy adults in the United States, but often occurs in adults with alcoholism or intestinal malabsorption problems. Zinc levels also may be problematic in the elderly, pregnant women, diabetics, AIDS patients, and those with chronic infections and/or trauma. Low plasma zinc has been found in patients with alcoholic cirrhosis, Crohn's disease, and celiac disease. Experimental studies with humans have shown that the signs of zinc deficiency are detectable after two to five weeks of consumption of the zinc-free diet. The signs include a rash and diarrhea. The rash occurs on the face, groin, hands, and feet. These symptoms can easily be reversed by administering zinc. Absorption of zinc is largely dependent on the presence or absence of other foods that affect zinc absorption. Meats, liver, eggs, and seafood are good choices of zinc because these foods do not contain many other components which interfere with zinc absorption. An emerging concern is that increased calcium intake can interfere with zinc absorption or retention. Hence, there is some interest in the question of whether persons taking calcium to prevent osteoporosis should also take zinc supplements.

Copper deficiency

Copper deficiency is relatively uncommon but severe alterations in copper metabolism occur in two genetic diseases, Wilson's disease and Menkes' disease. Both of these diseases are rare. Menkes' disease occurs in about one in 50,000 to 100,000 births while Wilson's disease occurs in approximately one in 200,000 births in the United States. Both diseases involve mutations in copper transport proteins, that is, in special channels that allow the passage of copper ions through cell membranes. Menkes' disease is a genetic disease involving mental retardation and death before the age of three years. The disease also results in steely or kinky hair. The hair is tangled, grayish, and easily broken. Menkes' disease involves a decrease in copper levels in the serum, liver, and brain, and increases in copper in the cells of the intestines and kidney.

The richest sources of copper are shellfish, nuts, seeds, cocoa powder, liver, organ meats, legumes, and the germ and bran portions of grains.

Selenium deficiency

Selenium deficiency may occur in premature infants, since this population naturally tends to have low levels of plasma selenium. Full term infants have plasma selenium levels of about 0.001-0.002 mmol/L, while premature infants may have levels about one third this amount. Whether these lower levels result in adverse consequences is not clear. Total parental nutrition often leads to selenium deficiency if it is not administered in the fluids. 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. Keshan disease, which may be fatal, is thought to result from a combination of selenium deficiency and a virus.

The richest sources of selenium are organ meats and seafood. In addition, muscle meats, cereals and grains, dairy products, and fruits and vegetables provide good sources of selenium.

Other ultratrace mineral deficiencies

Manganese deficiency is very rare. Experimental studies with humans fed a manganese deficient diet have revealed that the deficiency produces a scaly, red rash on the skin of the upper torso. The importance of manganese in human nutrition still needs to be established. It is thought that the possibility in becoming manganese deficient is increased in alcohol abusers. Molybdenum deficiency has probably never occurred, but indirect evidence suggests that if molybdenum deficiency could occur, it would result in mental retardation and death.

There is some evidence that other inorganic nutrients, such as chromium and boron, play a part in human health, but their role is not well established. Chromium has a function related to insulin and thus influences carbohydrate, lipid, and protein metabolism. Boron is believed to affect macromineral metabolism in humans. Fluoride has been proven to increase the strength of bones and teeth, but there is little or no reason to believe that is needed for human life.

Diagnosis

The diagnosis of deficiencies in water, sodium, potassium, iron, calcium, and phosphate involve chemical testing of the blood plasma, urine, and red blood cells. Hypocalcemia is usually first discovered during routine blood tests because often there are no symptoms evident.

Iodine deficiency can be diagnosed by measuring the concentration of iodine in the urine. A urinary level greater than 0.05 mg iodine per gram creatinine means adequate iodine status. Levels under 0.025 mg iodine/g creatinine indicate a serious risk.

There is no reliable test for zinc deficiency. When humans eat diets containing normal levels of zinc (16 mg/day), the level of urinary zinc is about 0.45 mg/day, while humans consuming low-zinc diets (0.3 mg/day) may have urinary levels of about 0.150 mg/day. Plasma zinc levels tend to be maintained during a dietary deficiency in zinc. Plasma and urinary zinc levels can be influenced by a variety of factors, and for this reason cannot provide a clear picture of zinc status.

Selenium deficiency may be diagnosed by measuring the selenium in plasma (70 ng/mL) or red blood cells (90 ng/mL), where the normal values are indicated. There is also some interest in measuring the activity of an enzyme in blood platelets, in order to assess selenium status. This enzyme is glutathione peroxidase. Platelets are small cells of the bloodstream which are used mainly to allow the clotting of blood after an injury.

Treatment

The treatment of deficiencies in sodium, potassium, calcium, phosphate, and iron often involves intravenous injections of the deficient mineral. Potassium, however, usually can be replaced relatively easily by eating foods rich in potassium or by taking potassium salts (potassium chloride) orally.

Iodine deficiency can be easily prevented and treated by fortifying foods with iodine. Table salt is fortified with 100 mg potassium iodide per kg sodium chloride. Goiter was once common in the United States in areas from Washington State to the Great Lakes region, but this problem has been eliminated by iodized salt. Public health programs in impoverished countries have administered injections of synthetic oils containing iodine. Goiter is reversible, but cretinism is not.

Magnesium deficiency can be treated with a magnesium rich diet. If magnesium deficiency is due to a prolonged period of depletion, treatment may include injections of magnesium sulfate (2.0 mL of 50% MgSO₄). Where magnesium deficiency is severe enough to provoke convulsions, magnesium needs to be administered by injections or infusions. For infusion, 500 mL of a 1% solution (1 gram/100 mL) of magnesium sulfate is gradually introduced into a vein over the course of about five hours. When hypomagnesemia occurs along with hypocalcemia, the magnesium must be replaced before successful treatment of the calcium disorder.

Zinc deficiency and copper deficiency are quite uncommon, but when they are detected or suspected, they can be treated by consuming zinc or copper, on a daily basis, at levels defined by the RDA.

Selenium deficiency in adults can be treated by eating 100 mg selenium per day for a week, where the selenium is supplied as selenomethionine. The incidence of Keshan disease in China has been reduced by supplementing children with 1.0 mg sodium selenite per week.

Prognosis

In iodine deficiency, the prognosis for treating goiter is excellent, however, cretinism cannot be reversed. The effects of iron deficiency are not life-threatening and can be easily treated. The prognosis for treating magnesium deficiency is excellent. The symptoms may be relieved promptly or, at most, within two days of starting treatment. In cases of zinc deficiency in Iran and other parts of the Middle East, supplementation of affected young adults with zinc has been found to provoke the growth of pubic hair and enlargement of genitalia to a normal size within a few months.

Health care team roles

Mineral deficiencies are normally diagnosed and treated by physicians. Dieteticians may be employed in efforts of patient education. For example, the dietetician may counsel a patient about a healthy diet to prevent further deficiencies, or be involved in community programs to educate the public at large.

Prevention

In the healthy population, all mineral deficiencies can be prevented by the consumption of inorganic nutrients at levels defined by the Recommended Dietary Allowances (RDA) or Dietary Reference Intakes (DRI). Where a balanced diet is not available, government programs for treating individuals, or for fortifying the food supply, may be used. Government sponsored programs for the prevention of iron deficiency and iodine deficiency are widespread throughout the world. Selenium treatment programs have been used in parts of the world where selenium deficiency exists. Attention to potassium status, and to the prevention of potassium deficiency, is an issue mainly in patients taking diuretic drugs. In many cases of mineral deficiency, the deficiency occurs because of disease, and individual medical attention, rather than preventative measures, is used. Calcium supplements are widely used with the hope of preventing osteoporosis. The prevention of deficiencies in magnesium, copper, manganese, or molybdenum are not major health issues in the United States. Ensuring an adequate intake of these minerals, by eating a balanced diet or by taking mineral supplements, is the best way to prevent deficiencies.

KEY TERMS

Dehydration— A deficit of body water that results when the output of water exceeds intake.

Diuretic— An agent or drug that eliminates excessive water in the body by increasing the flow of urine.

Electrolyte— A substance such as an acid, bases, or salt. An electrolyte's water solution will conduct an electric current and ionizes. Calcium, potassium, magnesium, and sodium are electrolytes.

Homeostatis— An organism's regulation of body processes to maintain internal equilibrium in temperature and fluid content.

Recommended Dietary Allowance— The Recommended Dietary Allowances (RDAs) are quantities of nutrients that are required each day to maintain human health. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences and may be revised every few years. A separate RDA value exists for each nutrient. In 2001, the RDA will be replaced by the Dietary Reference Intakes (DRI) and will apply to Americans and Canadians.

Resources

BOOKS

Brody, Tom. Nutritional Biochemistry. San Diego, CA: Academic Press, 1998.

Institute of Medicine, ed. Dietary Reference Intakes: Risk Assessment (Compass Series). Washington: National Academy Press, 1999.

Larson-Duyff, Roberta. The American Dietetic Association's Complete Food & Nutrition Guide. New York: John Wiley & Sons, 1998.

Murray, Michael T. Encyclopedia of Nutritional Supplements: The Essential Guide for Improving Your Health Naturally. Rocklin, CA: Prima Publishing, 2001.

National Academy Press Food and Nutrition Board Recommended Dietary Allowances, 10th edition. Washington: National Academy Press, 1989.

PERIODICALS

Foote, J. A., A. R. Giuliano, and R. B. Harris. "Older Adults Need Guidance to Meet Nutritional Recommendations." Journal of the American College of Nutrition 19, no. 5 (Oct. 2000): 628-40.

Fryer, M. J. "Selenium and Human Health." Lancet 356, no. 9233 (Sept. 9, 2000): 943.

Lonnerdal, B. "Dietary Factors Influencing Zinc Absorption." Journal of Nutrition 130, no. 5S Suppl (May 2000): 1378S-83S.

Rayman, M. P. "The Importance of Selenium to Human Health." Lancet 356, no. 9225 (Jul 15, 2000): 233-41.

ORGANIZATIONS

American Dietetic Association. 216 W. Jackson Blvd. Chicago, IL 60606-6995. (312) 899-0040. 〈http://www.eatright.org/〉.

Food and Nutrition Information Center Agricultural Research Service, USDA. National Agricultural Library, Room 304, 10301 Baltimore Avenue, Beltsville, MD 20705-2351. (301) 504-5719. Fax (301) 504-6409. 〈http://www.nal.usda.gov/fnic/〉. [email protected].

OTHER

Food and Nutrition Professionals Network. 〈http://nutrition.cos.com/〉.

Mineral Deficiency

Definition

The term mineral deficiency means 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 to an impairment in a function dependent on the mineral. In other cases, the convention may be to define an abnormally low mineral concentration as a level lower than that found in a specific healthy population.

The mineral nutrients are defined as all the inorganic elements or inorganic molecules that are required for life. As far as human nutrition is concerned, the inorganic nutrients include water, sodium, potassium, chloride, calcium, phosphate, sulfate, magnesium, iron, copper, zinc, manganese, iodine, selenium, and molybdenum. Some of the inorganic nutrients, such as water, do not occur as single atoms, but occur as molecules. Other inorganic nutrients that are molecules include phosphate, sulfate, and selenite. Phosphate contains an atom of phosphorus. Sulfate contains an atom of sulfur. We do not need to eat sulfate, since the body can acquire all the sulfate it needs from protein. Selenium occurs in foods as selenite and selenate.

There is some evidence that other inorganic nutrients, such as chromium and boron, 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 is needed for human life.

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 with the eyes and hands. In the case of iron deficiency, the diagnosis may include the performance of a stair-stepping test by the patient. Since all the minerals serve strikingly different functions in the body, the tests for the corresponding deficiency are markedly different from each other.

Description

Laboratory studies with animals have revealed that severe deficiencies in any one of the inorganic nutrients can result in very specific symptoms, and finally in death, due to the failure of functions associated with that nutrient. In humans, deficiency in one nutrient may occur less often than deficiency in several nutrients. A patient suffering from malnutrition is deficient in a variety of nutrients. In the United States, malnutrition is most often found among severe alcoholics. In part, this is because the alcohol consumption may supply half of the energy requirement, resulting in a mineral and vitamin intake of half the expected level. Deficiencies in one nutrient do occur, for example, in human populations living in iodine-poor regions of the world, and in iron deficient persons who lose excess iron by abnormal bleeding.

Inorganic nutrients have a great 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 to severe diarrhea and other causes. Iodine deficiency is a global public health problem. 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 only use of iodine in the body is for making thyroid hormone. However, since thyroid hormone has a variety of roles in development of 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 hence vitamin D deficiency in growing infants and children can result in calcium deficiency.

Dietary phosphate deficiency is rare because phosphate is plentiful in plant and animal foods, but also because phosphate is efficiently absorbed from the diet 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 is uncommon, but when it occurs it 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 is rare, but it has been found in impoverished populations in the Middle East, who rely on unleavened whole wheat bread as a major food source. 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. Low-selenium soils can produce foods that are also low in selenium. Premature infants may also be at risk for selenium deficiency. Manganese deficiency is very rare. Experimental studies with humans fed a manganese deficient diet have revealed that the deficiency produces a scaly, red rash on the skin of the upper torso. Molybdenum deficiency has probably never occurred, but indirect evidence suggests that if molybdenum deficiency could occur, it would result in mental retardation and death.

Causes and symptoms

Sodium deficiency (hyponatremia ) and water deficiency are the most serious and widespread deficiencies in the world. These deficiencies tend to arise from excessive 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, where they result from 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. Shock nearly always occurs when dehydration is severe enough to produce a 10% reduction in body weight. Shock, which is defined as inadequate supply of blood to the various tissues of the body, results in a lack of oxygen to all the cells of the body. Although diarrheal fluids contain a number of electrolytes, 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. Diuretics work because they cause loss of sodium from the body. These drugs are used to treat high blood pressure (hypertension ), where the resulting decline in blood pressure reduces the risk for cardiovascular disease. However, diuretics can lead to sodium deficiency, resulting in low plasma sodium levels. A side effect of some diuretics is excessive loss of potassium, and low plasma potassium (hypokalemia ) may result.

Iodine deficiency tends to occur in regions of the world where the soil is poor in iodine. Where soil used in agriculture is poor in iodine, the foods grown in the soil will also be low in iodine. An iodine intake of 0.10-0.15 mg/day is considered to be nutritionally adequate, while iodine deficiency occurs at below 0.05 mg/day. 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 foods with iodine. Iodine deficiency during pregnancy results in cretinism in the newborn. Cretinism involves mental retardation, a large tongue, and sometimes deafness, muteness, and lameness.

Iron deficiency occurs due to periods of dietary deficiency, rapid growth, and excessive loss of the body's iron. Human milk and cow milk both contains low levels of iron. Infants are at risk for acquiring iron deficiency because their rapid rate of growth needs a corresponding increased supply 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 deficiency are generally limited to anemia, and the resulting tiredness, weakness, and a reduced ability to perform physical work.

Calcium and phosphate are closely related nutrients. About 99% of the calcium and 85% of the phosphate in the body occur in the skeleton, where they exist as crystals of solid calcium phosphate. Both of these nutrients occur in a great variety of foods. Milk, eggs, and green, leafy vegetables are rich in calcium and phosphate. Whole cow milk, for example, contains about 1.2 g calcium and 0.95 g phosphorus per kg of food. Broccoli contains 1.0 g calcium and 0.67 g phosphorus per kg food. Eggs supply about one third of the calcium and phosphate of the overall population of the United States. 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 others who may be shielded from sunshine for prolonged periods of time. Vitamin D deficiency impairs the absorption of calcium from the diet, and in this way 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 energy intake in these areas. This diet, which does not contain meat, does contain zinc, but it also contains phytic acid at a level of about 3 g/day. The phytic acid, which naturally occurs in wheat, inhibits zinc absorption. The yeast used to leaven bread produces enzymes that inactivate the phytic acid. Unleavened bread does not contain yeast, and therefore, contains intact phytic acid. The symptoms of zinc deficiency include lack of sexual maturation, lack of pubic hair, and small stature. The amount of phytic acid in a typical American diet cannot provoke zinc deficiency.

Zinc deficiency is relatively uncommon in the United States, but it may occur in adults with alcoholism or intestinal malabsorption problems. Low plasma zinc has been found in patients with alcoholic cirrhosis, Crohn's disease, and celiac disease. Experimental studies with humans have shown that the signs of zinc deficiency are detectable after two to five weeks of consumption of the zinc-free diet. The signs include a rash and diarrhea. The rash occurs on the face, groin, hands, and feet. These symptoms can easily be reversed by administering zinc. An emerging concern is that increased calcium intake can interfere with zinc absorption or retention. Hence, there is some interest in the question of 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 in about one in 100,000 births. Both diseases involve mutations in copper transport proteins, that is, in special channels that allow the passage of copper ions through cell membranes. Menkes' disease is a genetic disease involving mental retardation and death before the age of three years. The disease also results in steely or kinky hair. The hair is tangled, grayish, and easily broken. Menkes' disease involves a decrease in copper levels in the serum, liver, and brain, and increases in copper in the cells of the intestines and kidney.

Selenium deficiency may occur in premature infants, since this population naturally tends to have low levels of plasma selenium. Full term infants have plasma selenium levels of about 0.001-0.002 mM, while premature infants may have levels about one third this amount. Whether these lower levels result in adverse consequences is not clear. 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. Keshan disease, which may be fatal, is thought to result from a combination of selenium deficiency and a virus.

Diagnosis

The diagnosis of deficiencies in water, sodium, potassium, iron, calcium, and phosphate involve chemical testing of the blood plasma, urine, and red blood cells.

Iodine deficiency can be diagnosed by measuring the concentration of iodine in the urine. A urinary level greater than 0.05 mg iodine per gram creatinine means adequate iodine status. Levels under 0.025 mg iodine/g creatinine indicate a serious risk.

Normal blood serum magnesium levels are 1.2-2.0 mM. Magnesium deficiency results in hypomagnesemia, which is defined as serum magnesium levels below 0.8 mM. Magnesium levels below 0.5 mM provoke a decline in serum calcium levels. Hypomagnesemia can also result in low serum potassium. Some of the symptoms of hypomagnesemia, which include twitching and convulsions, actually result from the hypocalcemia. Other symptoms of hypomagnesemia, such as cardiac arrhythmias, result from the low potassium levels.

There is no reliable test for zinc deficiency. When humans eat diets containing normal levels of zinc (16 mg/day), the level of urinary zinc is about 0.45 mg/day, while humans consuming low-zinc diets (0.3 mg/day) may have urinary levels of about 0.150 mg/day. Plasma zinc levels tend to be maintained during a dietary deficiency in zinc. Plasma and urinary zinc levels can be influenced by a variety of factors, and for this reason cannot provide a clear picture of zinc status.

Selenium deficiency may be diagnosed by measuring the selenium in plasma (70 ng/mL) or red blood cells (90 ng/mL), where the normal values are indicated. There is also some interest in measuring the activity of an enzyme in blood platelets, in order to assess selenium status. This enzyme is glutathione peroxidase. Platelets are small cells of the bloodstream which are used mainly to allow the clotting of blood after an injury.

Treatment

The treatment of deficiencies in sodium, potassium, calcium, phosphate, and iron usually involves intravenous injections of the deficient mineral.

Iodine deficiency can be easily prevented and treated by fortifying foods with iodine. Table salt is fortified with 100 mg potassium iodide per kg sodium chloride. Goiter was once common in the United States in areas from Washington State to the Great Lakes region, but this problem has been eliminated by iodized salt. Public health programs in impoverished countries have involved injections of synthetic oils containing iodine. Goiter is reversible but, cretinism is not.

Magnesium deficiency can be treated with a magnesium rich diet. If magnesium deficiency is due to a prolonged period of depletion, treatment may include injections of magnesium sulfate (2.0 mL of 50% MgSO₄). Where magnesium deficiency is severe enough to provoke convulsions, magnesium needs to be administered by injections or infusions. For infusion, 500 mL of a 1% solution (1 gram/100 mL) of magnesium sulfate is gradually introduced into a vein over the course of about five hours.

Zinc deficiency and copper deficiency are quite rare, but when they are detected or suspected, they can be treated by consuming zinc or copper, on a daily basis, at levels defined by the RDA.

Selenium deficiency in adults can be treated by eating 100 mg selenium per day for a week, where the selenium is supplied as selenomethionine. The incidence of Keshan disease in China has been reduced by supplementing children with 1.0 mg sodium selenite per week.

Prognosis

In iodine deficiency, the prognosis for treating goiter is excellent, however cretinism cannot be reversed. The effects of iron deficiency are not life-threatening and can be easily treated. The prognosis for treating magnesium deficiency is excellent. The symptoms may be relieved promptly or, at most, within two days of starting treatment. In cases of zinc deficiency in Iran and other parts of the Middle East, supplementation of affected young adults with zinc has been found to provoke the growth of pubic hair and enlargement of genitalia to a normal size within a few months.

Prevention

In the healthy population, all mineral deficiencies can be prevented by the consumption of inorganic nutrients at levels defined by the Recommended Dietary Allowances (RDA). Where a balanced diet is not available, government programs for treating individuals, or for fortifying the food supply, may be used. Government sponsored programs for the prevention of iron deficiency and iodine deficiency are widespread throughout the world. Selenium treatment programs have been used in parts of the world where selenium deficiency exists. Attention to potassium status, and to the prevention of potassium deficiency, is an issue mainly in patients taking diuretic drugs. In many cases of mineral deficiency, the deficiency occurs because of disease, and individual medical attention, rather than preventative measures, is used. The prevention of calcium deficiency is generally not an issue or concern, however calcium supplements are widely used with the hope of preventing osteoporosis. The prevention of deficiencies in magnesium, zinc, copper, manganese, or molybdenum are not major health issues in the United States. Ensuring an adequate intake of these minerals, by eating a balanced diet or by taking mineral supplements, is the best way to prevent deficiencies.

Resources

BOOKS

Brody, Tom. Nutritional Biochemistry. San Diego: Academic Press, 1998.

KEY TERMS

Recommended Dietary Allowance— The Recommended Dietary Allowances (RDAs) are quantities of nutrients that are required each day to maintain human health. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences and may be revised every few years. A separate RDA value exists for each nutrient.

mineral deficiency Lack of any essential mineral nutrient, such as nitrogen, phosphorus, or potassium, in living organisms, which can result in mineral deficiency diseases. In humans, for example, lack of calcium causes poor bone development, and lack of nitrogen can cause the disease kwashiorkor, due to a deficiency in protein intake (see malnutrition). In plants mineral deficiency results in stunted growth and chlorosis. A deficiency of trace elements (see essential element) also leads to diseases; for example, a deficiency of iron can cause anaemia in humans and chlorosis in plants.