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Iron absorption can be tricky


My "iron deficiency in adolescent girls" column caused a stir that needs clarification. Increased iron intake is a boon to younger people, but a threat to some older adults.

Who is at risk for iron deficiency?

The column reviewed a Johns Hopkins School of Medicine study showing iron deficiency might affect adolescent girls' memory and learning ability, then suggested food sources of iron to prevent or combat deficiency.

One distressed dad noted that boys can be iron deficient, too. And he's right. In the United States, iron deficiency affects 4 percent to 12 percent of boys aged 11 through 14, as well as 9 percent of children between 1 and 2 years, and 5 percent to 14 percent of women aged 15 to 44.

In fact, Dr. Benjamin Caballero, director of the Johns Hopkins Center for Human Nutrition, reminds us that iron deficiency is the most common nutritional deficiency in the world.

If you have fatigue, weakness, headaches, apathy, irritability, palpitations, reduced exercise ability, poor tolerance to cold, and pale color, visit your doctor and be tested for both iron deficiency and anemia. Request a serum ferritin test for storage iron, which is not routinely done.

Generally, people become iron deficient because they don't eat enough food, or not enough iron-rich foods, or because their bodies can't absorb enough iron from the food they do eat. In most people, iron absorption is well controlled, so they absorb more when stores are low, less when stores are high.

Normally, you'll consume the bulk of your iron from plant foods. However, plant-based iron is not well absorbed. Although adding fruits and vegetables high in vitamin C to meals will increase the amount of iron you absorb from those foods, the total is still only 3 percent. Diets with fiber above 35 grams/day further reduce iron absorption. On the other hand, you'll absorb 15 percent of the iron from lean meat, chicken and fish.

Who is at risk for iron overload?

About 1 percent of adults over age 45 suffer from iron overload. According to Dr. Victor Herbert,overload can result from a genetic flaw (hemochromotosis), or from repeated blood transfusions, massive excesses of dietary iron, alcoholism or rare metabolic disorders. Dr. Herbert is professor of medicine and chairman of the committee to Strengthen Nutrition at the Mount Sinai School of Medicine and Medical Center, and director of the Hematology and Nutrition Laboratory of Bronx Veterans Affairs Medical Center, Bronx, N.Y.

In the Journal of the American Dietetic Association, Dr. Herbert says that for those people, iron supplements and megadoses of vitamin C increase iron overload, irreversibly damaging heart, liver, joints, pancreas, gonads and other organs. Cancer, impotence, arthritis and diabetes often follow.

Older adults usually are not screened for iron overload. Screenings are necessary since both iron deficiency and iron overload have the common symptoms of low hemoglobin and anemia. The difference, according to Dr. Herbert, is in the levels of storage iron or serum ferritin.

Some recent studies also suggest high levels of iron in the blood may trigger a heart attack. More research is needed, but older adults can cut risks by avoiding vitamin supplements containing iron. Once you absorb it, you can't get rid of it.

Dr. Andrew Nicholson, director of preventive medicine at the Physicians Committee for Responsible Medicine, took issue with recommendation that red meat is a good source of iron for adolescent girls. The Physicians Committee for Responsible Medicine is an animal-rights group with few physician members.

In a letter to the editor he applied facts about the 1 percent of older people with iron overload to recommendations for younger people at risk for iron deficiency.

Dr. Nicholson's comment: " iron from meat defies the body's attempts to regulate its absorption, leading to dangerous excesses of iron."

Fact: Most bodies easily regulate iron absorption from all foods. Women and children at risk for iron deficiency don't over-absorb iron from meat. Only that 1 percent of older adults in iron overload get more than they need from all sources.

His comment: " populations that consume little or no animal products actually have equal or greater iron intake than meat eaters."

Fact: Intake, yes. But absorption? Dr. Herbert notes vegetarians are at twice the risk of iron deficiency as nonvegetarians.

Colleen Pierre, a registered dietitian, is the nutrition consultant at the Union Memorial Sports Medicine Center and Vanderhorst & Associates in Baltimore.

Pub Date: 12/03/96

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