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United States Department of Agriculture

Agricultural Research Service

Iron and the Battle of the Sexes
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Janet Hunt

"We could sell bread in pink or blue wrappers," joked a dietitian friend of mine as we discussed the problem of fortifying foods with iron to prevent iron deficiency in women without risking iron toxicity in men. It’s another battle of the sexes: Women of childbearing age are more likely to become iron deficient, while men are at greater risk of too much iron.

In a recent study of nearly 400 premenopausal women in the Grand Forks area, 4 percent were anemic and 20 percent had no storage iron, as indicated by very low serum ferritin. Although there are no known adverse effects of low iron stores, some storage iron is probably desirable to support future pregnancies. Where a little is good, however, more may not be better. One in four adult men have serum ferritin concentrations above those associated with increased risk of heart disease in a highly publicized Finnish 1992 study. Scientists are now investigating whether high iron stores increase the risk of chronic diseases, such as cancer and heart disease, by promoting oxidative damage to body cells.

More research is also needed on what influences iron stores so that we can best prevent or modify iron stores if they prove to increase disease risk. Genes certainly play a role: One in 300 people of European origin have a genetic abnormality for storing excessive amounts of iron, which leads to liver and heart disease. Blood donation and oral contraceptives also influence iron stores. Serum ferritin concentrations are lower in people who donate blood and higher in women who use oral contraceptives. But neither vitamin C, which increases iron absorption from a meal, nor a moderate intake of red meat--an excellent source of easily-absorbable iron--increase iron stores, according to studies done at the Grand Forks Human Nutrition Research Center, operated by the U.S. Department of Agriculture’s Agricultural Research Service.

We are currently conducting two studies at the center to why body iron stores aren’t increased by eating these foods or nutrients in short-term studies. One study tests whether the body’s iron absorption efficiency adapts to the diet depending on whether it promotes or reduces iron absorption. In that study, men living in the community let us provide everything they eat for 12 weeks. We will know they have adapted if the men eating a diet with lots of meat and foods rich in vitamin C tend to reduce their iron absorption after several weeks, and those eating less meat and lots of whole grains and tea, which interfere with iron absorption, increase their iron absorption.

The second study tests whether differences in long-term, self-selected dietary patterns of individual women influence serum ferritin, after accounting for other factors that could affect iron stores, such as blood donation and the use of oral contraceptives or iron supplements. Participants are required to give a blood sample for determining serum ferritin, answer a diet questionnaire and record everything they eat for one week.

While research on what influences iron stores continues, the advice to eat a variety of foods in moderation, following the food guide pyramid, applies to both sexes. The moderate iron enrichment of our bread and cereal products is especially likely to benefit women and children. Men and women past menopause would be wise to avoid nutrient supplements containing iron without a doctor’s specific recommendation to treat iron deficiency.

Last Modified: 4/4/2007
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