Several studies conducted as early as two decades ago documented altered iron status in athletes, yet questioned whether such alterations were physiologically detrimental. Wijn et al.¹⁰ measured Hb, packed cell volume, serum iron, and iron-binding capacity of selected athletes and compared these with the hematologic profile of officials during the 1968 Olympic games. These data illustrated an iron-deficient anemia in 2 percent of male and 2.5 percent of female athletes and a mild anemia without signs of iron depletion in 3 percent of the athletic population. Many other experiments have demonstrated a significant decrease in RBC number and a decrease in Hb, but often the runners were not affected. Subsequent investigations have supported these early studies and have demonstrated a reduction in Hb and HCT in certain athletic populations.

Several investigators have proposed mechanisms by which iron balance could be affected by intense physical exercise.¹¹ Explanations include increased gastrointestinal blood losses following running, and hematuria as a result of erythrocyte rupture within the foot during running.¹²

A growing body of evidence suggests that the prevalence of iron deficiency without anemia is increased in female athletes. Contributing to this observation is an increased iron loss through regular menstrual function as well as putative dietary factors. Given these observations, if exercise does further compromise iron status, then it would logically follow that the population of chronically | exercising female athletes may be at greater risk of developing iron deficiency. A summary of surveys demonstrates that 35 percent of female athletes have a serum ferritin concentration of less than 12 mg/L; 82 percent, less than 25 mg/L; and 60 percent, less than 30 mg/L, when compared with sedentary counterparts from the nonathletic female population. Although estimations of the precise prevalence rates differ, an increased incidence of reduced serum ferritin seems to be a repeatable observation between laboratories in this population. These results may be influenced by menstrual flow, and may additionally be affected by dietary iron intake. Taken together, these investigations illustrate a statistically significant difference between female athletes and control populations. What these investigations do not demonstrate, however, is a clinically subnormal or reduced serum ferritin concentration concurrent with a demonstrated functional consequence in the absence of overt anemia.

The Recommended Dietary Allowances (RDAs) are designed for the maintenance of good nutrition of practically all healthy people, and they define intakes of iron for infants, children, men and women, and also consider additional needs during pregnancy and lactation. From the data presented in this review, the following recommendations broadly apply to the three groups that appear to be at greatest risk of developing altered body iron given the data available. These recommendations do not assume that a deficiency will exist in these populations when consuming the RDA. However, a deficiency may be more likely, thus warranting closer dietary monitoring and regularly scheduled hematologic evaluations in these at-risk groups.