Iron supplementation in athletes—first do no harm

Abstract

Although it generally does not improve performance, iron is often used by elite athletes. The physiologic changes induced by exercise can mimic iron deficiency and decrease hemoglobin and ferritin concentrations. Determination of serum transferrin receptor concentrations may identify true iron deficiency, which occurs particularly in young athletes. In contrast, increased iron stores in the body are a frequent finding in elite athletes who have used long-term iron supplementation. Elite runners have increased intestinal blood loss, but this usually can be compensated by enhanced absorption of dietary iron. The combination of exercise-induced hemolysis with enhanced intestinal blood loss in various endurance sports leads to severe abnormalities of routine tests, and extreme physical activity may be responsible for positive fecal occult blood determinations. Indiscriminate iron supplementation carries the risk of inducing hemochromatosis in individuals homozygous for the widespread C282Y allele of the HFE gene. This polymorphism is common and can be found in about 1% of individuals of Northern European descent; moreover, iron supplementation can modify the presentation of important underlying diseases such as celiac disease or colon carcinoma. In conclusion, iron supplements should be prescribed for athletes with iron-deficiency anemia and carefully monitored if given for prophylaxis; unless a therapeutic response occurs, investigations to establish the cause of iron deficiency should be initiated.

Introduction

Iron as an emblem of strength and power originated in Greek mythology, where Hephestos was the god of fire and iron. Thus, over the centuries, iron therapy was tested in a variety of medical conditions and, at least in chlorosis (an archaic term for some causes of iron-deficiency anemia), it improved strength, power, and other manifestations of anemia.1 We address the questions of whether iron is beneficial in athletes and whether there is a rationale for supplementation of diets with iron during training and for competitive events.

Improvement and maintenance of physical and mental fitness and maximal performance are the principal dietary requirements demanded by athletes. Supplementation of proteins, carbohydrates,2 lipids,3 vitamins,4 and trace elements have been studied and reviewed for their effect on athletic performance in power and endurance sports.5, 6, 7 The focus of this article is to summarize current knowledge of the adaptive changes in iron metabolism of athletes during training and to review available evidence for the effect of dietary iron supplementation on physical performance.