Is meeting the recommended dietary allowance (RDA) for protein related to body composition among older adults? Results from the Cardiovascular Health of Seniors and Built Environment Study

Objective: Studies suggest protein intake may be associated with lower body weight, but protein has also been associated with preservation of lean body mass. Understanding the role of protein in maintaining health for older adults is important for disease prevention among this population. Design: Cross-sectional study of the relationship of dietary protein on body composition. Setting: New York City community centers. Participants: 1,011 Black, White, and Latino urban men and women 60-99 years of age. Measurements: Protein intake was assessed using two interviewer-administered 24-hour recalls, and body composition was assessed using bioelectrical impedance analysis (BIA) of fat mass (kg) (FM), fat free mass (kg) (FFM), and impedance resistance (Ohms). Statistical Analysis: Indices of FM and FFM were calculated by dividing BIA measurements by height squared (m²), and percent FFM was calculated by dividing FFM by the sum of FM and FFM. Log linear models adjusting for age (continuous), race/ethnicity, education, physical activity (dichotomized at the median), hypertension, diabetes, and total calories (continuous). Results: Just 33% of women and 50% of men reported meeting the RDA for protein. Both fat free mass index (FFMI) and fat mass index (FMI) were negatively associated with meeting the RDA for protein (Women: FFMI -1.78 95%CI [-2.24, -1.33], FMI -4.12 95% CI [-4.82, -3.42]; Men: FFMI -1.62 95% CI [-2.32, -0.93] FMI -1.80 95% CI [-2.70, -0.89]). After accounting for confounders, women and men consuming at least 0.8 g/kg/day had a 6.2% (95% CI: 5.0%, 7.4%) and a 3.2% (95% CI 1.1%, 5.3%) higher percent fat free mass, respectively. Conclusions: FFM, FFMI, FM, and FMI were inversely related to meeting the RDA for protein. Meeting the RDA for protein of at least 0.8g/kg/day was associated with a higher percentage of fat free mass among older adults. These results suggest meeting the protein recommendations of at least 0.8 g/kg/day may help to promote lower overall body mass, primarily through loss of fat mass rather than lean mass.