Self-reported protein intake and properties of bone in community-dwelling older individuals

SUMMARY: This study revealed that a quick and simple estimation of protein intake was related to measures of bone density and area in 70-year-old individuals. Furthermore, these associations were mediated by muscle mass when investigating peripheral measurement sites such as arms and legs. PURPOSE: Recent evidence suggests that dietary protein is beneficial for bone health in older individuals, but less is known about the influence of muscle mass on this relationship. This cross-sectional study aimed to investigate associations among protein intake, bone health, and muscle mass in 2332 men and women aged 70 years. METHODS: Volumetric bone mineral density of the radius and tibia was measured using peripheral quantitative computed tomography. Using dual-energy X-ray absorptiometry, we measured areal bone mineral density (aBMD) at the L1–L4 vertebrae, radius, and femoral neck, together with appendicular lean mass. Participants reported their average meal size and proportion of meat/fish intake. Associations were investigated using multiple linear regression models, adjusted for multiple covariates. RESULTS: Self-reported protein intake was associated with aBMD of the femoral neck (β = 0.082) and L1–L4 vertebrae (β = 0.063) in men (both p < 0.05) after adjusting for multiple covariates, including appendicular muscle mass. No significant association was detected among women. In addition, protein intake was associated with tibial cortical area (β = 0.08), periosteal circumference (β = 0.072), radial aBMD (β = 0.064), and trabecular area (β = 0.078) in men (all p < 0.05), although these associations were attenuated after adjustment for appendicular muscle mass (all p > 0.05). CONCLUSION: Self-reported protein intake was associated with bone properties in 70-year-old men. The strength of these associations in peripheral bone sites may be partially mediated by muscle mass from protein intake.