Development of Runner's Anemia during a 20-Day Road Race: Effect of Iron Supplements

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Abstract
Intense training for long-distance running has been associated with reduced hemoglobin (Hb) levels and low iron stores. Whether iron supplementation helps prevent this “runner's anemia” remains controversial. To determine the relationship between iron status and the early stage of reduced Hb levels in male runners, we examined hematologic variables in 15 healthy men (ages 25 to 47 yrs) who ran twice their regular training distance in 20 days during a 500-km road race. Nine of the runners took iron-containing tablets which provided an average of 36 mg/d of iron, while the other six did not take iron supplements. Only one of the 15 subjects had a low Hb concentration (< 14 g/dl) before the race. After 10 days (285 km), low Hb levels (p < 0.001) were found in 12/15; six of these runners took iron supplements. However, following a 2-day rest period and five more days of running, only 5/15 and 7/15, respectively, had low Hb levels. Serum iron, ferritin, total iron binding capacity, and percent transferrin saturation values remained within normal limits and did not change significantly. Reticulocyte counts progressively increased, becoming 8-fold higher than at baseline (p < 0.001), irrespective of the use of iron supplements. “Runner's anemia” developed in 11/15 (73%) of the subjects, independently of their iron status and iron intake. The reductions in Hb were accompanied by parallel decreases in RBC count and hematocrit, and by a significant reticulocytosis. It was concluded that the development of low Hb levels in these runners was acute in origin, partly reversible with rest, not prevented by iron supplementation, and therefore probably due to a functional hemodilution.

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