Effects of long-distance running on iron metabolism and hematological parameters

In 110 well-trained participants of a 1000-km running competition lasting for 20 days hematological parameters, iron metabolism, and their respective changes during the race were investigated. Thirty-nine men and 11 women were accustomed to wholesome vegetarian food (lacto-ovovegetarian), 52 men and 8 women consumed a conventional western diet. In each group 50% of the runners finished the race. Before the competition started red blood cell count, hematocrit, and hemoglobin were on average below the values observed in the normal population in all groups. Both male and female runners consuming the wholesome diet showed significantly lower ferritin values than those on a western diet. During the first days of the competition hemolysis occurred leading to increased serum concentrations of bilirubin and iron and decreased haptoglobin levels. Hb concentrations showed a constant decrease during the race. Serum ferritin concentration rose about twofold within the first days and then decreased again without reaching pre-race levels. Serum iron concentrations showed a significant decrease between days 3 and 6. Iron loss was caused by hematuria (25% of all urines tested), gastrointestinal blood loss (10% of all stool specimens tested), and by sweating (4.5 micrograms iron/dl sweat). Our results suggest that especially in female long-distance runners it may be difficult to supply sufficient quantities of iron with the diet.