Vitamin D and the Risk of Stress Fractures in Athletes and Military Personnel: A Systematic Review and Meta-analysis

Abstract

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 (R² = 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.