Vitamin D metabolites are associated with musculoskeletal injury in young adults: a prospective cohort study.

The relationship between vitamin D metabolites and lower body (pelvis and lower limb) overuse injury is unclear. In a prospective cohort study, we investigated the association between vitamin D metabolites and incidence of lower body overuse musculoskeletal and bone stress injury in young adults undergoing initial military training during all seasons. In 1637 men and 530 women (age, 22.6 ± 7.5 years; BMI, 24.0 ± 2.6 kg∙m -2 ; 94.3% white ethnicity), we measured serum 25-hydroxyvitamin D (25(OH)D) and 24,25-dihydroxyvitamin D (24,25(OH) 2 D) by high-performance liquid chromatography tandem mass spectrometry, and 1,25-dihydroxyvitamin D (1,25(OH) 2 D) by immunoassay during week 1 of training. We examined whether the relationship between 25(OH)D and 1,25(OH) 2 D:24,25(OH) 2 D ratio was associated with overuse injury. During 12 weeks training, 21.0% sustained ≥1 overuse musculoskeletal injury, and 5.6% sustained ≥1 bone stress injury. After controlling for sex, BMI, 2.4 km run time, smoking, bone injury history, and Army training course (Officer, standard, or Infantry), lower body overuse musculoskeletal injury incidence was higher for participants within the second lowest versus highest quartile of 24,25(OH) 2 D (OR: 1.62 [95%CI 1.13-2.32; P = 0.009]) and lowest versus highest cluster of 25(OH)D and 1,25(OH) 2 D:24,25(OH) 2 D (OR: 6.30 [95%CI 1.89-21.2; P = 0.003]). Lower body bone stress injury incidence was higher for participants within the lowest versus highest quartile of 24,25(OH) 2 D (OR: 4.02 [95%CI 1.82-8.87; P < 0.001]) and lowest versus highest cluster of 25(OH)D and 1,25(OH) 2 D:24,25(OH) 2 D (OR: 22.08 [95%CI 3.26-149.4; P = 0.001]), after controlling for the same covariates. Greater conversion of 25(OH)D to 24,25(OH) 2 D, relative to 1,25(OH) 2 D (i.e., low 1,25(OH) 2 D:24,25(OH) 2 D), and higher serum 24,25(OH) 2 D were associated with a lower incidence of lower body overuse musculoskeletal and bone stress injury. Serum 24,25(OH) 2 D may have a role in preventing overuse injury in young adults undertaking arduous physical training. This article is protected by copyright. All rights reserved.