Carswell AT, Swinton P, O'Leary TJ, Jackson S, Tang JCY, Oliver SJ, Wentz LM, Izard RM, Taylor N, Allan D, Rhodes LE, Walsh NP, Fraser WD, Greeves JP.
The British journal of nutrition · 2026
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Abstract
In 250 men (21·4 (sd 2·9) years; BMI 24·2 (sd 3·0) kg·m -2 ) commencing arduous military training during winter, we investigated the effect of 12 weeks of vitamin D supplementation on lower body (pelvic girdle, sacrum, coccyx and lower limb) overuse musculoskeletal injury risk in a randomised, placebo-controlled trial. Participants received either simulated sunlight (1·3 × standard erythemal dose in T-shirt and shorts, three times per week for 4 weeks and then once per week for 8 weeks), oral vitamin D 3 (1000 IU · d -1 for 4 weeks and then 400 IU · d -1 for 8 weeks) or placebo for each intervention. Serum vitamin D metabolites and bone metabolism biomarkers were measured at baseline, week 5 and week 12. At baseline, 29 % of participants were vitamin D sufficient (25-hydroxyvitamin D ≥ 50 nmol·L -1 ). Vitamin D supplementation achieved vitamin D sufficiency in 95 % of participants after 4 weeks. During 6 months of training and subsequent 3 years of military service, 100 lower body overuse musculoskeletal injuries were diagnosed by clinicians. Frailty models indicated no difference in injury risk between vitamin D and placebo during military training (HR placebo:vitamin D = 1·23 (95 % CI 0·57, 2·66), P = 0·597) or military service (HR placebo:vitamin D = 0·94 (95 % CI 0·60, 1·46), P = 0·782). Both safe simulated sunlight and oral vitamin D 3 were effective in achieving and maintaining vitamin D sufficiency in almost all. There was no clear evidence that vitamin D affects the risk of lower body overuse musculoskeletal injury during 6 months of military training or subsequent 3 years of military service.