Impact of baseline serum ferritin and supplemental iron on altitude-induced hemoglobin mass response in elite athletes.

Abstract

The present study explored the impact of pre-altitude serum (s)-ferritin and iron supplementation on changes in hemoglobin mass (ΔHbmass) following altitude training. Measures of Hbmass and s-ferritin from 107 altitude sojourns (9-28days at 1800-2500m) with world-class endurance athletes (males n=41, females n=25) were analyzed together with iron supplementation and self-reported illness. Altitude sojourns with a hypoxic dose [median (range)] of 1169 (912) km·h increased Hbmass (mean±SD) 36±38g (3.7±3.7%, p<0.001) and decreased s-ferritin -11 (190) µg·L-1 (p=0.001). Iron supplements [27 (191) mg·day-1 ] were used at 45 sojourns (42%), while only 11 sojourns (10%) were commenced with s-ferritin <35µg/L. Hbmass increased by 4.6±3.7%, 3.4±3.3%, 4.2±4.3%, and 2.9±3.4% with pre-altitude s-ferritin ≤35µg·L-1 , 36-50µg·L-1 , 51-100µg·L-1 , and >100µg·L-1 , respectively, with no group difference (p=0.400). Hbmass increased by 4.1±3.9%, 3.0±3.0% and 3.7±4.7% without, ≤50mg·day-1 or >50mg·day-1 supplemental iron, respectively (p=0.399). Linear mixed model analysis revealed no interaction between pre-altitude s-ferritin and iron supplementation on ΔHbmass (p=0.906). However, each 100km·h increase in hypoxic dose augmented ΔHbmass by an additional 0.4% (95% CI: 0.1-0.7%; p=0.012), while each 1g·kg-1 higher pre-altitude Hbmass reduced ΔHbmass by -1% (-1.6 to -0.5; p<0.001), and illness lowered ΔHbmass by -5.7% (-8.3 to -3.1%; p<0.001). In conclusion, pre-altitude s-ferritin or iron supplementation were not related to the altitude-induced increase in Hbmass (3.7%) in world-class endurance athletes with clinically normal iron stores.