Dermal excretion of iron in intensely training athletes

The iron concentration in sweat and serum and related variables (transferrin saturation percentage, hemoglobin concentration) was measured in two groups of distance runners, each consisting of ten persons. In the first group unclear sweat was collected from the back of the athletes during cycling (without previous washing). The iron concentration (means +/- SEM) was 5.2 +/- 1.0 mumol/l of sweat. In the second group the sweat collection was performed similarly, but following elimination of the very first sweat from the site of collection (back) before three consecutive samples were taken. The iron concentration of the three samples was 3.6 +/- 1.1, 2.3 +/- 0.2 and 2.4 +/- 0.3 mumol/1. There was no statistically significant difference between the consecutive samples on the p less than 0.001 level. These results are in accordance with the lowest values found in the literature. There was no correlation between the iron concentration in sweat and in serum of the 20 persons. Seven of the runners had transferrin saturation percentages below 20, suggesting a possible iron deficiency. A daily loss in sweat of more than 18 mumol (1 mg) is possible in these runners training 125-350 km/week all the year round. The dominating iron loss of male endurance athletes is probably through the sweat.