The Impact of Protein Source on Bone Density, Structure and Body Composition in the VITamin D and OmegA-3 TriaL (VITAL)

Abstract

Purpose: The relationship between different dietary sources of protein on bone structure, bone strength, and body composition has not been well established. We examined the association between different protein source intakes (total, animal, dairy, and plant) and bone mineral density, bone structure, bone strength, and body composition within the VITamin D and OmegA-3 TriaL (VITAL) bone health ancillary study. Methods: VITAL is a 2x2 factorial, randomized-controlled trial investigating the effects of a median of 5-years of moderately, high-dose supplemental vitamin D3 (2000 IU/day) and/or omega-3 fatty acids (1 g/day) for the primary prevention of cancer and cardio- vascular disease within 25,874 men (aged ≥ 50 years) and women (aged ≥ 55 years) in the U.S. A subcohort of 771 participants in the VITAL: Effects on Bone Structure and Architecture ancillary study underwent baseline and 2-year follow-up measurements of bone density and body composition using dual-energy X-ray absorptiometry (DXA), and bone structure and bone strength using peripheral quantitative computed tomography (pQCT). Dietary protein intakes were assessed using a validated food frequency questionnaires at baseline and 2-years follow-up. Results: Mean total protein intake at baseline was 32.58 servings per week of which 38% was animal protein (i.e, meat, chicken, turkey and fish), 10% was plant protein, and 52% was dairy protein. Higher total protein and animal protein intakes were positively associated with appendicular lean mass. Higher total protein intakes were also negatively associated with fat mass index and cortical density at the radius. These associations remained significant after adjusting for age, sex, race, body mass index, and physical activity. There was no significant association between protein source intake and bone mineral density, trabecular bone score, and bone strength. Conclusions: Greater total protein intakes are associated with decreased fat mass index and increased appendicular lean mass, with no associations with bone mineral density or bone strength. These findings contribute to the growing evidence that high protein intake may have beneficial effects on body composition and protect against sarcopenia.