Dermal excretion of iron in intensely training athletes.
Level 4 - case-series / case-control
Small observational cross-sectional physiological study without a randomized intervention or control group.
PubMed 6825307 · doi:10.1016/0009-8981(83)90071-2
What was done
Iron concentration in sweat, serum iron, transferrin saturation, and hemoglobin were measured in two groups of 10 distance runners during cycling exercise. In the first group, sweat was collected from the back without prior skin washing. In the second group, the initial sweat was discarded before collecting three consecutive sweat samples from the back.
What was found
Mean (± SEM) iron concentration in unwashed sweat was 5.2 ± 1.0 µmol/L. When initial sweat was eliminated, consecutive sweat iron concentrations were 3.6 ± 1.1, 2.3 ± 0.2, and 2.4 ± 0.3 µmol/L (differences not statistically significant at p < 0.001). There was no correlation between sweat iron and serum iron concentrations across the 20 runners. Seven of 20 runners had transferrin saturation below 20%.
Why it matters
It demonstrates that dermal excretion can be a major route of iron loss in endurance athletes, with daily sweat losses potentially exceeding 18 µmol (1 mg) during high-mileage training.
Limits
Small sample size (20 distance runners), lack of a sedentary control group, and sweat was sampled from a single anatomical region (the back), which may not represent whole-body sweat loss. Total daily sweat volume and iron loss were estimated rather than directly quantified.
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