Summary
This gene-environment interaction study in 192 Royal Marines recruits (51 with stress fractures, 141 uninjured controls) demonstrates that low serum vitamin D status increases stress fracture risk during intensive military training, with protective effects modulated by vitamin D receptor genotype. Recruits with stress fractures failed to show the rise in 25OHD concentration observed in uninjured controls between weeks 1–15, and higher mid-training vitamin D status was independently associated with reduced fracture risk. The findings suggest that baseline vitamin D status and VDR genotype interact to influence fracture vulnerability, supporting prophylactic vitamin D supplementation as an injury prevention strategy in high-physical-demand populations.
UK applicability
Given that this study was conducted in the United Kingdom with Royal Marines recruits, the findings are directly applicable to UK military training and occupational health policy. The results support consideration of vitamin D screening and supplementation protocols within UK armed forces and may inform injury prevention strategies for other UK populations undertaking intensive physical training, particularly during winter months when dermal vitamin D synthesis is limited.
Key measures
Serum 25-hydroxyvitamin D (25OHD) concentration (nmol/L) at weeks 1, 15, and 32; VDR FokI polymorphism genotype; stress fracture incidence and timing; adjusted odds ratios for fracture risk per 1 SD increase in 25OHD; allele frequency distribution
Outcomes reported
The study measured serum 25-hydroxyvitamin D (25OHD) concentrations at three timepoints during a 32-week Royal Marines training programme and genotyped participants for the vitamin D receptor (VDR) FokI polymorphism to assess their association with stress fracture incidence. Stress fracture risk was evaluated in relation to vitamin D status and VDR genotype, including gene-environment interactions.
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