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Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc
iron-loading abnormalities, particularly thalassemias; congenital atransferrinemia; and aceruloplasminemia (Fairbanks, 1999). These individuals may not be protected by the UL for iron. A UL for subpopulations such as persons with hereditary hemochromatosis can not be determined until information on the relationship between iron intake and the risk of adverse effects from excess iron stores becomes available.
A body of experimental evidence suggests that intermittent dosing (once or twice per week) of iron supplements may be an effective means of controlling iron deficiency in developing countries (Beaton and McCabe, 1999). Under these circumstances, individuals receiving intermittent doses of iron supplements may exceed the UL. The effects of intermittent dosing on gastrointestinal side effects has not been studied adequately.
Based on distribution data from NHANES III (Appendix Table C-19), the highest median reported intake of iron from food and supplements for all life stage and gender groups, excluding pregnancy and lactation, was approximately 19 mg/day. This was the median intake reported by men 31 through 50 years of age. The highest intake from food and supplements at the ninetieth percentile reported for any life stage and gender group, excluding pregnancy and lactation, was approximately 34 mg/day for men 51 years of age and older. This value is below the UL of 45 mg/day. Between 50 and 75 percent of pregnant and lactating women consumed iron from food and supplements at a level greater than 45 mg/day, but iron supplementation is usually supervised in pre- and postnatal care programs.
Based on a UL of 45 mg/day of iron for adults, the risk of adverse effects from dietary sources appears to be low. Gastrointestinal distress does not occur from consuming a diet containing naturally occurring or fortified iron. Individuals taking iron salts at a level above the UL may encounter gastrointestinal side effects, especially when taken on an empty stomach. Twenty-five percent of men aged 31 to 50 years in the United States have ferritin concentrations greater than 200 μg/L (Appendix Table G-3), which may be a risk factor for cardiovascular disease (Sullivan, 1981). This prevalence is higher in men older than 50 years. However, the significance of