Abstract
Objectives
While an increasing number of studies highlight the significance of vitamin D supplementation for athletic performance, the effects of short-term high-dose vitamin D
3
supplementation on exercise-induced inflammation remain unclear. This study aimed to evaluate the effects of 21 days of vitamin D
3
supplementation (10,000 IU/day) on inflammatory biomarkers and maximal anaerobic performance in physically active men performing the 2 × Wingate Anaerobic Test (2xWAnT).
Methods
Thirty physically active men were randomly assigned in a double-blind manner to a vitamin D
3
group (10,000 IU/day in vegetable oil; n = 15; aged 24.21 ± 4.35) or a placebo group (vegetable oil; n = 15; aged 23.15 ± 3.44). During the supplementation period, one participant from the vitamin D
3
group and two from the placebo group were excluded because of non-compliance, leaving 27 participants for the final analyses (vitamin D
3
, n = 14; placebo, n = 13). Venous blood samples were collected at rest, immediately after, 3 h after, and 24 h after the 2xWAnT, before and after the 21-day intervention.
Results
Resting 25(OH)D increased by +55.7% after supplementation in the vitamin D
3
group. Wingate outcomes showed no differential effect of vitamin D
3
versus placebo on anaerobic performance. At rest, vitamin D
3
supplementation was associated with lower IL-1β and IL-6 concentrations and higher IL-10 concentrations. After the 2xWAnT, the vitamin D
3
group showed an attenuated IL-1β response, lower IL-1RA concentrations during the post-exercise period, and higher IL-10 concentrations across the post-exercise period. In contrast, despite the pronounced exercise-induced increase in IL-6, the post-exercise time course of this biomarker did not differ between groups.
Conclusions
Twenty-one days of vitamin D
3
supplementation increased serum 25(OH)D concentrations but did not improve anaerobic performance. Supplementation was associated with changes in selected resting and post-WAnT inflammatory biomarkers, suggesting modulation of the biochemical inflammatory response to repeated supramaximal anaerobic exercise. Functional recovery outcomes were not assessed.