Supplementary Energy Increases Bone Formation during Arduous Military Training

Purpose This study aimed to investigate the effect of supplementary energy on bone formation and resorption during arduous military training in energy deficit. Methods Thirty male soldiers completed an 8-wk military combat course (mean +/- SD, age = 25 +/- 3 yr, height = 1.78 +/- 0.05 m, body mass = 80.9 +/- 7.7 kg). Participants received either the habitual diet (control group, n = 15) or an additional 5.1 MJ center dot d(-1) to eliminate the energy deficit (supplemented group, n = 15). Circulating markers of bone formation and resorption, and reproductive, thyroid, and metabolic status, were measured at baseline and weeks 6 and 8 of training. Results Bone-specific alkaline phosphatase decreased in controls (-4.4 +/- 1.9 mu g center dot L-1) and increased in the supplemented group (16.0 +/- 6.6 mu g center dot L-1), between baseline and week 8 (P < 0.001). Procollagen type 1 N-terminal propeptide increased between baseline and week 6 for both groups (5.6 +/- 8.1 mu g center dot L-1, P = 0.005). Beta carboxy-terminal cross-linking telopeptide of type 1 collagen decreased between baseline and week 8 for both groups (-0.16 +/- 0.20 mu g center dot L-1, P < 0.001). Prolactin increased from baseline to week 8 for the supplemented group (148 +/- 151 IU center dot L-1, P = 0.041). The increase in adiponectin from baseline to week 8 was higher in controls (4.3 +/- 1.8 mg center dot L-1, P < 0.001) than that in the supplemented group (1.4 +/- 1.0 mg center dot L-1, P < 0.001). Insulin-like growth factor binding protein-3 was lower at week 8 than baseline for controls (-461 +/- 395 ng center dot mL(-1), P < 0.001). Conclusion The increase in bone-specific alkaline phosphatase, a marker of bone formation, with supplementation supports a role of energy in osteoblastic activity; the implications for skeletal adaptation and stress fracture risk are unclear. The mechanism is likely through protecting markers of metabolic, but not reproductive or thyroid, function.

Automated summary

Supplementary energy can enhance bone formation, but the implications for skeletal adaptation and stress fracture risk are still unclear. The mechanism likely involves protecting markers of metabolic function, rather than reproductive or thyroid function.