High-Dose Vitamin D Supplementation and Exercise Effects on Vitamin D Metabolites in Professional Football Players

Overview

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.

This pilot study was designed to explore the combined effects of high-dose vitamin D₃ supplementation and acute physical exercise on vitamin D metabolism in professional football players. The study responds to growing scientific interest in understanding how vitamin D status influences performance, recovery, and muscle function in athletes. While most previous studies have focused on chronic, low-to-moderate supplementation, this trial examined the response to a single, pharmacological dose of cholecalciferol in a controlled experimental setting. Study Design The study employed a randomized, single-blind, placebo-controlled, parallel-group design. Participants were randomly assigned to one of two groups: Supplementation Group (SGP) - received a single oral dose of 500,000 IU vitamin D₃ (Vigantol Oil, P\&G Health, Germany); Placebo Group (PGP) - received an identical amount of placebo (vegetable oil). The supplementation was administered 48 hours before a standardized intra-squad football match (ISG), conducted under conditions simulating a competitive game. All players followed the same training schedule and diet during the study. Participants A total of 20 professional male football players (aged 18-35) from a Polish top-league club volunteered to participate. Inclusion criteria included active professional status, regular training participation, and no use of vitamin D or calcium supplements in the previous 3 months. Exclusion criteria included musculoskeletal injuries, metabolic disorders, or refusal to sign informed consent. Measurements Blood samples were collected at three time points: T3: baseline (before supplementation), T4: 48 hours post-supplementation (pre-match), T5: immediately after the intra-squad game. Serum concentrations of 25-(OH)D₃, 24,25-(OH)₂D₃, and 3-epi-25-(OH)D₃ were determined using LC-MS/MS. Additional biochemical variables (hemoglobin, glucose, testosterone, cortisol, ferritin, calcium, CK) were analyzed to monitor physiological status. Outcomes Primary Outcome: Changes in serum 25-(OH)D₃ concentrations after supplementation and exercise. Secondary Outcomes: Changes in 24,25-(OH)₂D₃ and 3-epi-25-(OH)D₃ levels, metabolite ratios. Ethics The study was approved by the Ethics Committee of the Wroclaw University of Health and Sport Sciences (Resolution No. 1/2024, March 1, 2024). All participants signed written informed consent.