Vitamin D and tibial bone density, geometry, and microarchitecture in male military recruits: An observational study and randomized controlled trial

O'Leary, Thomas J., Izard, Rachel M., Jackson, Sarah, Walsh, Neil P., Carswell, Alexander T., Oliver, Samuel J., Allan, Donald, Rhodes, Lesley E., Tang, Jonathan C. Y., Fraser, William D. and Greeves, Julie P. (2025) Vitamin D and tibial bone density, geometry, and microarchitecture in male military recruits: An observational study and randomized controlled trial. Journal of Bone and Mineral Research. ISSN 0884-0431

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Abstract

Vitamin D may mitigate bone stress injuries in military training by modulating changes in bone. This cross-sectional observational study (Study 1) and randomized controlled trial (Study 2) investigated associations between vitamin D metabolites and tibial structure and density, and the effect of vitamin D supplementation on tibial adaptations to military training. A total of 343 (Study 1) and 194 (Study 2) male British Army recruits participated. Circulating vitamin D metabolites (biologically “active” and “inactive”) and tibial structure were measured in participants during week 1 and week 12 (Study 2 only) of initial military training. Associations between vitamin D metabolites and HRpQCT outcomes at week 1 were tested in Study 1. Participants in Study 2 were randomly assigned to vitamin D (oral pill or simulated sunlight) or placebo (placebo pill or placebo simulated sunlight) supplementation for 12 wk designed to achieve vitamin D sufficiency. There was no association between total 25(OH)D or vitamin D receptor single-nucleotide polymorphisms and any measure of density, geometry, or microarchitecture (p ≥ .063). Higher 1,25(OH)2D was associated with lower cortical porosity and perimeter (p ≤ .040). Higher total 24,25(OH)2D was associated with higher trabecular number and lower trabecular thickness (p = .016). Higher 25(OH)D:24,25(OH)2D (VMR 1) was associated with higher trabecular thickness, trabecular separation, and cortical porosity (p ≤ .034). Higher 1,25(OH)2D:24,25(OH)2D (VMR 2) was associated with lower trabecular number, and higher trabecular spacing and thickness (p ≤ .035). There was no effect of vitamin D supplementation on any tibial outcome. Training decreased trabecular area (−0.1%), thickness (−4.4%), and separation (−2.1%), and increased cortical thickness (0.8%) and area (0.9%) (p ≤ .042). Vitamin D metabolites and their ratios were associated with tibial size and microarchitecture, but vitamin D supplementation had no impact on the adaptive response to military training.

Item Type:	Article
Additional Information:	Data availability statement: Pending approval from the UK Ministry of Defence, the data that support the findings of this study will be made available from the corresponding author. Funding information: This study was funded by the UK Ministry of Defence (Army).
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School
Related URLs:	https://academic.oup.com/jbmr/advance-ar...
Depositing User:	LivePure Connector
Date Deposited:	18 Jun 2025 13:30
Last Modified:	22 Jun 2025 05:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99630
DOI:	10.1093/jbmr/zjaf064

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