Association Between Serum Vitamin D Levels and Stress Fracture Risk in Athletes and Military PersonnelLower Vitamin D Levels Linked to Higher Stress Fracture Risk

BACKGROUND: Stress fractures are common overuse injuries in military personnel and athletes. Although a low vitamin D level is a proposed risk factor, the evidence is conflicting, and the specific risk in athletes has not been systematically synthesized. PURPOSE: To assess the association between vitamin D status and the risk of stress fractures in military personnel and athletes. STUDY DESIGN: Systematic review and meta-analysis; Level of evidence, 3. METHODS: Major databases were systematically searched through April 16, 2025 for studies that quantitatively measured serum levels of 25-hydroxyvitamin D in military or athlete populations with a stress fracture group and a control group. Data were pooled using a random-effects model to calculate the mean difference (MD) and 95% confidence interval (CI). Subgroup analyses were conducted based on population type (military vs athlete), sex, and vitamin D status. Meta-regression was also performed to investigate sources of heterogeneity. RESULTS: A total of 15 studies (4183 participants) were included. Overall, patients with stress fractures had significantly lower vitamin D levels compared to controls (MD, -5.82 nmol/L [95% CI, -10.35 to -1.29]). The association was also significant for military personnel (MD, -7.33 nmol/L [95% CI, -11.77 to -2.89]) and male participants (MD, -9.14 nmol/L [95% CI, -14.23 to -4.06]). Subgroup analyses of female participants and athletes did not detect a statistically significant difference in vitamin D levels. Meta-regression identified baseline vitamin D status as a significant moderator, explaining over half of the between-study heterogeneity ( = 53.8%). The subgroup analysis based on baseline vitamin D status revealed that the association between lower vitamin D levels and stress fractures was present only in the subgroup in which control participants were already vitamin D sufficient (MD, -13.53 nmol/L [95% CI, -20.57 to -6.49]). CONCLUSION: A lower serum vitamin D level was associated with an increased risk of stress fractures, particularly in military personnel and male participants. The absence of a significant association in athletes and female participants warrants further investigation. These findings suggest that vitamin D status should be assessed in high-risk populations to guide preventive strategies focused on maintaining optimal levels.