Effects of vitamin D supplementation on vitamin D status and physical performance in football players: A systematic review and meta-analysis

Background/Objectives: Low vitamin D status is frequently reported among athletes, but whether vitamin D supplementation improves physical performance in football players remains uncertain. This systematic review and meta-analysis aimed to evaluate the effects of vitamin D supplementation on serum 25-hydroxyvitamin D [25(OH)D] concentration, jump performance, sprint performance, aerobic capacity, and muscular performance in association football and futsal players. Methods: PubMed, Embase, the Cochrane Library, Scopus, and Web of Science were searched from database inception to 31 May 2026. Controlled intervention studies comparing vitamin D supplementation with control conditions were eligible. Standardized mean differences were calculated as Hedges’ g and pooled using random-effects meta-analyses. Two reviewers independently extracted data and assessed risk of bias using RoB 2 or ROBINS-I. The certainty of evidence was assessed using GRADE. The protocol was prospectively registered in PROSPERO (CRD420261430873). Results: Eleven reports representing nine independent studies and 312 players were included. In RCT-only primary analyses, vitamin D supplementation was associated with higher circulating 25(OH)D concentrations (g = 1.41, 95% CI 0.90 to 1.92; I² = 58.0%). Pooled effects were not statistically significant for jump performance (g = 0.21, 95% CI −0.10 to 0.53), sprint performance (g = −0.03, 95% CI −0.40 to 0.34), aerobic capacity (g = 0.00, 95% CI −0.45 to 0.45), or muscular performance (g = 0.19, 95% CI −0.14 to 0.51). The certainty of evidence was low for circulating 25(OH)D, jump performance, and muscular performance, and very low for sprint performance and aerobic capacity. Conclusions: Vitamin D supplementation was associated with increased circulating 25(OH)D concentrations, whereas current evidence is insufficient to support a consistent improvement in physical performance. Given the low to very low certainty of evidence, these findings should be interpreted cautiously. Larger, well-designed randomized controlled trials using standardized, football-relevant performance tests are warranted.