Dietary Protein Intake and Its Associations With Bone Properties Using Peripheral Quantitative Computed Tomography and Dual-Energy X-Ray Absorptiometry in Endurance-Trained Individuals.

Background: Endurance athletes are at greater risk of compromised bone health due to elevated nutritional demands and high-volume training. Optimal nutritional intake is fundamental to support athlete bone health, and dietary protein is an essential nutrient for the maintenance of bone and muscle tissue. Studies of associations between dietary protein intake and advanced imaging-based measures of bone and muscle health in endurance athletes are limited.

Objectives: To examine the relationships between dietary protein intake and volumetric bone mineral density (vBMD), estimated bone strength (SSI and BSI), areal BMD (aBMD), and muscle density, cross-sectional area (CSA), and strength in male and female endurance-trained individuals.

Methods: Fifty healthy young endurance-trained adults completed one-time measures. Peripheral quantitative computed tomography (pQCT) scans assessed tibial trabecular and cortical vBMD, BSI, SSI, and calf muscle density and CSA. Dual-energy X-ray absorptiometry scans measured aBMD at the lumbar spine (LS) and proximal femur. Dietary protein intake (grams per kilogram of body mass per day) was calculated from 3-day 24-h dietary recalls.

Results: Bivariate analyses found no correlations between total dietary protein intake and pQCT-derived bone and muscle measures. However, protein intake from animal products was correlated with SSI at the 38% (r = 0.39, = 0.008) and 66% site (r = 0.44, = 0.002), cortical vBMD (r = -0.34, = 0.02) at the 66% site, and calf muscle CSA (r = 0.57, <.001). Adjusted regression analyses revealed that higher total dietary protein intake was associated with higher LS aBMD (β = 0.398, = 0.009).

Conclusions: Our findings suggest that there are no relationships between total dietary protein intake and pQCT measures in endurance-trained individuals. However, positive relationships were found with protein intake from animal products and tibial SSI and muscle CSA. Additionally, our results suggest total dietary protein intake explains a small variance in LS aBMD. A future larger-scale analysis would benefit from stratifying associations by sex.