Micronutrients in Health and Disease: Mineral Deficiencies

Iron. Deficiency of this mineral occurs with a frequency ranging from 2% of pubescent and adult males to 16% of menstruating females,¹⁶ and iron deficiency–related anemia is the most common cause of anemia in pregnancy.¹⁷ (See Iron Deficiency Anemia.)

Iron overload, although less common than iron deficiency, occurs in roughly 0.5% of Caucasians and results from hereditary hemochromatosis (HHC), an autosomal recessive disorder caused in most cases by the C282Y and H63D mutation in the HFE gene on chromosome 6p21.3.¹⁸ However, in spite of the frequency of this disorder, it is not by itself responsible for HHC–related diseases, such as diabetes and liver disease.¹⁹ Even in the absence of the gene for hemochromatosis, evidence shows that individuals in Western, meat–eating populations may have iron stores far in excess of those needed for health.²⁰ These individuals may be at greater risk for heart disease, cancer, and diabetes, risks that appear to be greatest among elderly persons.²¹ Among elderly participants in the Framingham Heart Study, 13% had high iron stores, while approximately 3% were found to have iron deficiency.²¹

Calcium. Intakes of calcium at levels significantly below dietary reference intakes (DRI) are common in a large segment of the U.S. population. After 10 years of age, both males and females get, on average, roughly half the recommended intake.²² A significant body of evidence, however, indicates that a more moderate calcium intake may be adequate. While calcium intakes below 400 mg per day may reduce bone development, intakes above this level do not appear to correlate to bone mineral density or to reduce fracture risk. Other factors, particularly targeted physical activity, do appear to more precisely reflect bone density in this population.²³ Data from the Nurses’ Health Study do not support the hypothesis that a higher total calcium or dairy calcium intake in adults is protective against hip or forearm fracture.²⁴

Concerns about high calcium intakes have arisen from studies indicating a higher risk of prostate cancer among men consuming more dairy products or calcium (see Prostate Cancer) and a higher risk of kidney stones under certain circumstances (see Kidney Stones).

Magnesium. Clinical deficiency of blood magnesium is rare in the general population, but it should be suspected in individuals with chronic diarrhea, patients with hypocalcemia or refractory hypokalemia, and those given certain medications (see below).^25,26 Individuals developing or having hypomagnesemia may show neuromuscular hyperexcitability,²⁵ and hypocalcemia is a sign of severe hypomagnesemia (< 1.0 mEq/L, 0.5 mmol/L).²⁶ Hypomagnesemia occurs in up to 12% of hospitalized patients and in as many as 60% to 65% of Intensive Care Unit (ICU) patients.²⁶ In the Third National Health and Nutrition Examination Survey (NHANES III), 68% of adults consumed less than the recommended daily allowance (RDA) for magnesium, and 19% consumed less than 50% of the RDA.²⁷ Hypomagnesemia was found in 27% of healthy lean children and 55% of obese children in one study,²⁸ and the condition occurs in 25% to 38% of individuals with diabetes.²⁹ (See Diabetes.) Magnesium deficiency may result from poor intake of foods rich in this mineral, such as green vegetables, nuts, seeds, dried beans, and whole grains.