Optimization of calcium and vitamin D status during initial military training: a randomized, double‐blind, placebo‐controlled trial (250.4)

Abstract

Poor vitamin D status is linked to musculoskeletal injuries, such as stress fracture, during military training. The objective of this trial was to determine the effect of daily calcium (Ca) and vitamin D supplementation (2000 mg and 800 IU/day, respectively) on biochemical indicators of nutritional status and bone health, including ionized Ca (iCa), serum vitamin D (25[OH]D), and parathyroid hormone (PTH) during initial military training (IMT). Biomarkers were assessed in volunteers (n = 164, males = 104, females = 60, age [mean ± SD] = 21 ± 4 yrs) at the start of IMT (PRE), and at the end of the 9‐wk course (POST). Supplemental Ca and vitamin D were provided in a fortified snack food, which was consumed 2x/day throughout IMT; overall compliance was 84%. As compared to placebo, Ca and vitamin D supplementation resulted in increased circulating iCa POST‐IMT (group X time interaction, P < 0.05), but not serum 25(OH)D. Increased PTH levels observed in the placebo group at the end of IMT (PRE vs. POST, P < 0.05; 28.5 ± 13.2 vs. 31.3 ± 16.3 pg/ml) were attenuated in the supplemented group (group X time interaction, P < 0.05; 26.9 ± 12.7 vs. 25.3 ± 13.7). Although serum 25(OH)D was not affected, these data indicate that supplementation with Ca and vitamin D during IMT resulted in positive changes in Ca status by preventing the mobilization of Ca from bone through stabilization of PTH. Research supported by USAMRMC.