Facts About Iron

Part 4: Current issues and controversies about iron.

Individuals with hereditary hemochromatosis are at increased risk for liver cancer(1). This increased risk is associated with an accumulation of iron in the liver, which can result in increased production of free radicals. Free radicals are by-products of normal metabolism that can damage your body’s cells. There is inconclusive evidence that iron status is associated with the incidence of cancer in those who do not have hereditary hemochromatosis.

Many men and women who engage in regular intense exercise have marginal or inadequate iron status(1,57-60). Researchers have estimated that daily iron loss increases in those who engage in regular exercise. Research also indicates that iron has a shorter biologic half-life in highly trained runners. For these reasons, the need for iron may be 30% greater in those who engage in regular intense exercise(61).

Some researchers have raised concerns about the effects of iron fortification and supplementation on the absorption of other nutrients such as zinc, calcium, and copper. Research studies have shown that supplemental iron may decrease the absorption of these nutrients, but generally only when the supplement is taken on an empty stomach. Absorption of these nutrients is generally not affected when supplementary iron is taken with food(1,62,63).

Iron has a moderate to high potential for toxicity because very little iron is excreted from the body. Thus, iron can accumulate in body tissues and organs when normal storage sites are full.

In children, acute toxicity can occur from overdoses of medicinal iron. Ingestion of as few as five or six high-potency tablets can provide amounts of iron that can be fatal to a child of 22 pounds. Consuming 1 to 3 grams of iron can be fatal to children under six and lower doses can cause severe symptoms such as vomiting and diarrhea (64). It is important to keep iron supplements tightly capped and away from children’s reach. Any time excessive iron intake is suspected, immediately call your physician or Poison Control Center, or visit your local emergency room. In adults high intakes of iron supplements are associated with constipation, nausea, vomiting, and diarrhea, especially when the supplements are taken on an empty stomach (1).

In 2001, the Institute of Medicine set a tolerable upper intake level (UL) of 40 mg per day for infants and children through age 13 and 45 mg per day for adolescents ages 14 to 18 years and adults 19 years of age and older (1). The upper limit does not apply to individuals who receive iron under medical supervision. There may be times when a medical doctor prescribes an intake higher than the upper limit, such as when individuals with iron deficiency anemia need higher doses of iron until their iron stores return to normal.

As the 2000 Dietary Guidelines for Americans state, “Different foods contain different nutrients and other healthful substances. No single food can supply all the nutrients in the amounts you need” (65). The following tables suggest dietary sources of heme and nonheme iron. As the table indicates, meat, poultry, fish and seafood are good sources of heme iron and beans are good sources of nonheme iron. In addition, many foods are fortified with iron. Some foods, such as cereals, may be fortified with 100% of the Daily Value (DV)* for iron. It is important for anyone who is considering taking an iron supplement to first consider whether their needs are being met by natural dietary sources of heme and nonheme iron and foods fortified with iron. If you want more information about building a healthful diet, refer to the Dietary Guidelines for Americans and the Food Guide Pyramid

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