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Bone, 2019; 123(): 224–233, PMID: 30902791

Calcium and vitamin D supplementation and bone health in Marine recruits: Effect of season.

Year: 2019

Gaffney-Stomberg E, Nakayama AT, Guerriere KI, Lutz LJ, Walker LA, Staab JS, Scott JM, Gasier HG, McClung JP
Military Performance Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760, United States of America. Electronic address:


Stress fractures are common overuse injuries caused by repetitive bone loading. These fractures are of particular concern for military recruits and athletes resulting in attrition in up to 60% of recruits that sustain a fracture. Army and Navy recruits supplemented with daily calcium and vitamin D (Ca+D) demonstrated improved bone strength and reduced stress fractures. The aim of the current study was to evaluate whether Ca+D supplementation improves measures of bone health in recruits undergoing United States Marine Corps initial military training (IMT), and whether the effect of supplementation on indices of bone health varied by season. One-hundred ninety-seven Marine recruits (n=107 males, n=90 females, mean age=18.9+/-1.6 y) were randomized to receive either Ca+D fortified snack bars (2000mg Ca and 1000IU vitamin D per day) or placebo divided into twice daily doses during 12weeks of IMT. Anthropometrics, fasted blood samples, and peripheral quantitative computed tomography (pQCT) scans of the tibial metaphysis and diaphysis were collected upon entrance to- and post-training (12weeks later). Half of the volunteers entered training in July and the other half started in February. Time-by-group interactions were observed for vitamin D status (25OHD) and the bone turnover markers, BAP, TRAP and OCN. 25OHD increased and BAP, TRAP and OCN all decreased in the Ca+D group (p<.05). Training increased distal tibia volumetric BMD (+1.9+/-2.8%), BMC (+2.0+/-3.1%), and bone strength index (BSI; +4.0+/-4.0%) and diaphyseal BMC (+1.0+/-2.2%) and polar stress strain index (SSIp; +0.7+/-2.1%) independent of Ca+D supplementation (p<.05 for all). When analyzed by season, change in BSI was 67% greater in the Ca+D group as compared to placebo in the summer iteration only (T*G; p<.05). When categorized by tertile of percent change in BSI, recruits demonstrating the greatest changes in BSI and 25OHD entered training with the lowest levels of 25OHD (p<.05). Taken together, these data suggest that Ca+D supplementation reduced indices of bone turnover and the decline in 25OHD over training in volunteers that started training in the summer was prevented by supplementation. Baseline 25OHD and trajectory may be important for optimizing skeletal health during IMT.

GID: 4885; Last update: 01.04.2019