Prevalence of Vitamin D Inadequacy in Athletes: A Systematic-Review and Meta-Analysis
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Vitamin D is essential for maintaining optimal bone health. The prevalence of vitamin D inadequacy in athletes is currently unclear.
The objective of this study is to determine the prevalence of vitamin D inadequacy in athletes.
We conducted a systematic review and meta-analysis. Multiple databases were searched and studies assessing serum 25-hydroxyvitamin D [25(OH)D] status in athletes were identified. Serum 25(OH)D is measured to clinically determine vitamin D status. Reviewers independently selected the eligible articles, assessed the methodological quality, and extracted data. Disagreements were resolved by consensus. Weighted proportions of vitamin D inadequacy [serum 25(OH)D <32 ng/mL] were calculated (DerSimonian–Laird random-effects model) and compared using Chi-squared (χ 2) test. Subgroup analyses were conducted and risk ratios (RRs) with 95 % confidence intervals (CIs) were reported.
Twenty-three studies with 2,313 athletes [mean (standard deviation) age 22.5 (5.0) years, 76 % male] were included. Of 2,313 athletes, 56 % (44–67 %) had vitamin D inadequacy that significantly varied by geographical location (p < 0.001). It was significantly higher in the UK and in the Middle East. The risk significantly increased for winter and spring seasons (RR 1.85; 95 % CI 1.27–2.70), indoor sport activities (RR 1.19; 95 % CI 1.09–1.30), and mixed sport activities (RR 2.54; 95 % CI 1.03–6.26). The risk was slightly higher for >40°N latitude [RR 1.14 (95 % CI 0.91–1.44)] but it increased significantly [RR 1.85 (1.35–2.53)] after excluding the Middle East as an outlier. Seven studies with 359 athletes reported injuries. The prevalence of injuries in athletes was 43 % (95 % CI 20–68) [bone related = 19 % (95 % CI 7–36); muscle and soft-tissue = 37.5 % (95 % CI 11.5–68.5)].
Despite the limitations of the current evidence, the prevalence of vitamin D inadequacy in athletes is prominent. The risk significantly increases in higher latitudes, in winter and early spring seasons, and for indoor sport activities. Regular investigation of vitamin D status using reliable assays and supplementation is essential to ensure healthy athletes. The prevalence of injuries in athletes is notable but its association with vitamin D status is unclear. A well-designed longitudinal study is needed to answer this possible association.
KeywordsSport Activity Middle Eastern External Quality Assessment Weighted Proportion Ballet Dancer
No sources of funding were used to assist in the preparation of this review. The authors have no potential conflicts of interest that are directly relevant to the content of this review. The authors would like to thank Nadia Latifi for assisting with resolving discrepancies during the study selection process.
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