Effects of iron supplementation on total body hemoglobin during endurance training at moderate altitude

The aim of the study was to test the hypothesis that iron supplementation i n well-trained non-iron-depleted athletes leads to an enhanced increase of total body hemoglobin (TBH) during training at moderate altitude. Therefore , the members of the national German boxing team were randomly assigned to treatment with ferrous-glycine-sulfate (1335 mg equivalent to 200 mg elemen tary iron daily) or with placebo during 18 days of endurance training at mo derate altitude (1800 m). Before and after altitude training TBH was determ ined by CO-rebreathing, measures of exercise performance were determined wi th an incremental treadmill test. Before, during and after the stay at mode rate altitude erythropoietin (Epo), reticulocytes (Retics) and parameters o f iron metabolism were measured in venous blood. The results show that TBH did not change significantly in the placebo-group and even slightly, but si gnificantly decreased in the iron-treated group. However, there was a signi ficant increase of Epo and Retics in both groups during training at moderat e altitude whereas parameters of iron metabolism remained unchanged. V(over dot)O-2 max did not change either. To test whether a training-induced hemo lysis, an increased urinary iron excretion or gastrointestinal blood loss c ould explain the unexpected drop of TBH we tested most of the boxers again during a similar training camp at low altitude (400-1000 m) to obtain measu res of hemolysis, urinary iron excretion and occult hemoglobin loss with th e stools. Although there were signs of an increased erythrocyte turnover no iron toss could be observed. We conclude that 18 days of endurance trainin g at an altitude of 1800 m does not lead to an increase of TBH in non-iron- depleted athletes with and without iron supplementation.