Iron supplements: More harm than good?

Dear Dr. Burke:

I am a professional cyclist who has been taking an iron supplement for several years. I have always been told to be careful of low iron levels in my blood.

Recently I read that too much iron can lead to symptoms similar to chronic fatigue and over training which I seem to suffer from too often. I eat a well-balanced diet including red meat about once a week. Can you set the record straight for iron supplementation?



Dear Jennifer:

While supplemental iron will boost sagging iron stores and alleviate anemia, you should not depend on iron as a preventive measure. Iron supplements contain anywhere from 30 to 200 milligrams, far enough over the recommended dietary allowance of 10 milligrams for men and 15 milligrams for women to cause side effects.

Most notably, iron pills lead to constipation in some individuals and diarrhea in others. As the dose increases, these discomforts worsen. Nausea and stomach pain can also occur, but will stop when iron use is discontinued.

Furthermore, excessive iron intake inhibits the absorption of zinc, a mineral that aids in healing and boosts the immune system. Because the body absorbs both iron and zinc through the intestinal tract, excess iron virtually bumps zinc out of the way.

Over 25 milligrams of iron at one meal is sufficient to cause problems with zinc absorption. Also, since research has shown that zinc status may be marginal for many athletes, iron supplementation could be doing more harm than good.

Perhaps the most alarming news about excess iron comes from Pacific Northwest Laboratories in Washington and the National Cancer Institute in Washington, D.C., where researchers found that people who store high amounts of iron have a greater risk of developing cancer.

In a 10-year study, scientists looked at a large group of men and women who were initially cancer-free. The male subjects who developed cancer showed higher iron stores than the men who remained cancer-free.

Cancer risk was 40 percent greater in men with high levels of iron in their bodies. The link between cancer risk and high iron stores was weaker among female subjects, perhaps because women typically have lower iron stores than men.

Since cancer cells need iron for growth, the researchers believe that lifelong iron intake may be a factor in cancer development.

They cautioned against iron supplements and heavily iron-fortified foods for those who are not anemic. While this study established no definitive link between diet and cancer risk, more research will follow to determine if excess dietary iron will be added to the long list of dietary substances that may cause cancer.

Therefore, don't take extra iron unless you need to. Pregnant women and those who are diagnosed as iron-deficient will certainly benefit from extra iron, but for all others, a balanced diet should meet your daily needs.

If you feel the need for "insurance," take a multivitamin/mineral supplement, which typically contains the USRDA of iron, 15 milligrams for women, 10 milligrams for men. This is a safe amount for those who usually don't meet their iron needs through diet.

By choosing the right foods, most people can easily meet their iron needs. Check your diet for iron-rich foods: lean red meat, dark-meat poultry, fish, dried beans, whole grains, dried fruit, enriched grain products and leafy green vegetables. And eat foods rich in vitamin C along with your meals to improve iron absorption.

Ask Ed Burke: How much base mileage do you need before interval training?

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