This randomized, single-blind, placebo-controlled pilot study investigated the effects of high-dose vitamin D₃ supplementation and football-specific physical exercise on vitamin D metabolite concentrations in professional male football players. The study aimed to evaluate the acute response of circulating vitamin D metabolites, including 25-(OH)D₃, 24,25-(OH)₂D₃, and 3-epi-25-(OH)D₃, following a single oral dose of 500,000 IU cholecalciferol combined with high-intensity intermittent exercise typical of competitive football.
Twenty professional football players from a Polish top-division club participated in the study. Participants were randomly assigned to either the supplementation group (SGP) receiving 500,000 IU of vitamin D₃ or the placebo group (PGP) receiving an identical volume of placebo oil. The intervention was administered 48 hours prior to an intra-squad game. Blood samples were collected at three time points: baseline (T3), pre-match (T4), and post-match (T5). The primary outcome was the change in serum 25-(OH)D₃ concentration. Secondary outcomes included changes in 24,25-(OH)₂D₃ and 3-epi-25-(OH)D₃ levels, as well as their ratios. The study also assessed whether physical exercise modulates vitamin D metabolism.
The findings demonstrated that high-dose vitamin D₃ supplementation significantly increased serum 25-(OH)D₃ (↑198%) and 3-epi-25-(OH)D₃ (↑444%) levels, while football-specific exercise itself induced moderate increases in vitamin D metabolites. The results suggest that skeletal muscle may play a key role in vitamin D storage and release in response to exercise. The supplementation was well tolerated, with no adverse events observed.