Endurance athletes, especially women, should take care to avoid iron deficiency

Low dietary intake of iron may be the most common nutritional deficiency for serious endurance athletes, especially women.

A 1988 study of female, high school cross-country runners found 45 percent had low iron stores. In the same study, 17 percent of the boys were low.

Other research showed that 31 percent of female, college athletes were iron-deficient. Up to 80 percent of women runners were below normal iron stores in a third study.

Commonly accepted, although still debated, causes of iron depletion include high-volume running on hard surfaces, too much anaerobic training, chronic use of aspirin, travel to high altitude, excessive menstrual flow, and a diet low in animal-food products.

Those most at risk, in the order of their risk, are runners, women, endurance athletes, vegetarians, those who sweat heavily, dieters and recent blood donors.

The symptoms of iron deficiency include loss of endurance, chronic fatigue, high exercise heart rate, low power, frequent injury, recurring illness, and an attitude problem. Since many of these symptoms are also common to overtraining, the athlete may cut back on exercise, feel better, and return to training only to find an almost immediate relapse.

If a deficiency is suspected, see your doctor. He or she may recommend a blood test to determine your iron status. A typical iron profile includes measures such as the following.

  • Ferritin (FERR): This is a marker of iron stores in the body. Low ferritin levels means that the body is losing iron. FERR values between 13 and 20 ug/ml indicate borderline iron deficiency.

  • Iron (FE): Most of the bodys iron is stored in the hemoglobin inside red blood cells. The amount of iron in the blood depends on the amount of dietary iron, how much is absorbed, and how much is lost. There can be wide daily fluctuations in blood FE levels.

  • Total Iron Binding Capacity (TIBC):This is an indicator of the bodys ability to transport iron to and from storage areas. Very high levels may indicate storage iron deficiency. Low levels are sometimes associated with inflammatory conditions.

  • Saturation (SAT): Transferrin is the substance that actually transports iron in the blood. There is usually more transferrin than iron. The percent of saturation of this transferrin is generally 20 to 40 percent. Below 20 percent suggests poor iron transport capability. This may result from low iron stores.

    Knowing one of the above is not enough to draw conclusions about your iron status, so your doctor will probably analyze more than one indicator. It is the pattern of these variables, often in combination with others, that is important in determining iron deficiency anemia.

    Should the test indicate abnormally low levels, an increased intake of iron is usually recommended. The RDA for women and teenagers is 15 milligrams per day. Men should consume 10 mg. Endurance athletes may need more.

    The normal North American diet contains about 6 mg of iron for every 1,000 calories, so an athlete restricting food intake to 2,000 calories a day while exercising strenuously can easily create a low-iron condition in a few weeks.

    Dietary iron comes from both animal meat and plant foods. The iron in animal sources has the best absorption rate at about 15 percent, but only about 5 percent of plant iron is taken up by the body. So the more effective way to increase iron status is by eating animal products, especially liver, which is rich in iron.

    Iron absorption from any foods, whether plant or animal, is decreased if they are accompanied at meals by egg, coffee, tea, wheat or cereal grains. Calcium and zinc also reduce the ability of the body to absorb iron. Including fruits, especially citrus fruit, in meals enhances iron absorption.

    Don't use iron supplements unless under the supervision of your doctor, as some people are susceptible to iron overload, a condition known as hemochromatosis. Also note that ingesting iron supplements is a leading cause of poisoning in children. Aspirin is first.

    References

    Hinton, P.S., et al. 2000. Iron supplementation improves endurance after training in iron-depleted, nonanemic women. Journal of Applied Physiology 88(3): 1103-1111.

    Rowland, T.W., et al. 1988, The effect of iron therapy on the exercise capacity of nonanemic iron-deficient adolescent runners. American Journal of Disease and Children 142(2): 165-169.

    Rowland, T.W., et al. 1991. Iron deficiency in adolescent girls. Are athletes at increased risk? Journal of Adolescent Health 12(1): 22-25.

    Seiler, D., et al. 1989. Effects of long-distance running on iron metabolism and hematological parameters. International Journal of Sports Medicine 10(5): 357-362.

    Van Handel, P.J. Whats in Your Blood? Sport Sciences Program of the US Olympic Committee.

    Zhu, Y.I., J.D. Haas. 1997. Iron depletion without anemia and physical performance in young women. American Journal of Clinical Nutrition 66(2): 334-341.

    Joe Friel is the author of the "Training Bible" series of books and is the founder and President of Ultrafit Associates. He may be reached at jfriel@ultrafit.com.

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