Effect of protein supplementation during a 6-month strength and conditioning program on areal and volumetric bone parameters.

BACKGROUND Skeletal loading and proper nutrition are necessary for optimal bone health. The appropriate amount of dietary protein to maximize skeletal health, however, is under constant debate. OBJECTIVE To determine if 6 months of protein supplementation in conjunction with a strength and conditioning training program improves areal and volumetric bone mineral density (BMD). DESIGN Fifty-two apparently healthy males and females ages 18-25 years were randomized to protein supplement (PRO, Myoplex, EAS, Inc. Golden CO) containing 280 kcal, 42 g protein, 21 g carbohydrate, and 1.5 g fat) or calorically equivalent carbohydrate control (CS). All subjects participated in a 5 sessions/week strength and conditioning program. Volumetric and areal BMD measurements were made by peripheral quantitative computed tomography (pQCT) of the tibia and whole body DXA. pSSI a measure of torsional bone strength, based on structural and material properties was obtained by pQCT. RESULTS Measurements at the 20% tibia by pQCT revealed that overall there were significant increases in cortical vBMD (4.3 +/- 1.3 mg/cm(3)), cortical area (1.9 +/- 0.6 cm(2)), cortical thickness (0.05 +/- 0.02 mm) and pSSI (67 +/- 24 mm(3)), and a decrease in endosteal circumference (- 0.5 +/- 0.2 mm) over the intervention period (all, P < 0.05). None of the changes in DXA measures were found to differ by group or sex, there was a trend for a greater increase in whole body BMC among the carbohydrate compared to protein supplemented group and a greater increase among males (16 +/- 8 g) compared to females (-9 +/- 9 g) (P = 0.06). CONCLUSIONS The results of this study indicate that the consumption of additional protein does not improve measurements of vBMD or bone size during a 6-month strength and conditioning program. Longer duration studies may be necessary to determine the influence of increased dietary protein on bone in young adults. Males and females may have different bone responses to increased protein intake while participating in a strength and conditioning program.