Beneficial Effects of Animal and Plant Proteins on Skeletal Muscle Mass and Functional Status
Authors: Moore Lynn L. , Bradlee M. Loring , Singer Martha R. 
Published: November 2023

Age‐related loss of muscle mass and related functional decline is directly related to a number of other negative outcomes including chronic disability, institutionalization, and diminished quality of life. Through its potential effects on skeletal muscle mass, dietary protein may provide some protection against the risk of functional decline. While clinical trials have tested the combined effects of protein supplementation and resistance exercise on muscle protein synthesis, fewer studies have directly examined the effects of dietary protein on functional status. The objective of the current analyses was to estimate the effects of total protein as well as animal and plant proteins on skeletal muscle mass during the middle‐adult years and on standardized measures of functional status and risk of disability/functional decline at older ages. We used subjects from the Framingham Offspring Study who provided two set of three‐day dietary records. Protein intake residuals were adjusted for body weight using a linear regression model. We then classified protein intake into three categories. The lowest protein intake category comprised <75 g/day for men, <65 g/day for women while the highest intake category included >100 g/day for men and >90 g/day for women. Analysis of covariance models were used to estimate the adjusted level of % skeletal muscle mass (from validated equations relying on bioelectrical impedance analysis). Among 1380 adults ages 30–54 years of age, after adjusting for age, sex, height, physical activity, smoking, and energy intake, we found that percent skeletal muscle mass (% SMM) increased as dietary protein intake increased (31.6%, 32.6%, 33.3% SMM, for those with low, moderate and high intakes of dietary protein). Both animal and plant proteins were similarly linearly associated with % SMM. We used Cox proportional hazards models to estimate the long‐term risk of developing sarcopenia according to intakes of animal and plant proteins. Subjects with the highest (vs. lowest) intakes of animal protein (>75 vs. <55 g/day for men, >65 vs. <40 g/day for women) had a 27% lower risk of sarcopenia (HR: 0.73; 95% CI: 0.60, 0.88) while those with the highest plant protein intakes (>25 g/day vs. <20 g/day) had a 23% lower risk of sarcopenia (HR: 0.77; 95% CI: 0.63, 0.95) than those with the lowest intakes of plant protein. Finally, among 1262 subject over the age of 50 years at baseline, we explored the effects of animal and plant proteins in combination with physical activity level on long‐term risk of functional decline. In these analyses, active older adults who consumed the most animal protein had a 29% lower risk (95% CI: 0.48, 1.02) of developing one or more functional deficits over 12 years of follow‐up. Similarly, active older adults who consumed the most plant protein had a 44% lower risk (95% CI: 0.38, 0.83) of developing one or more functional deficits over time. This study provides evidence showing that both animal and plant proteins play important roles in the maintenance of skeletal muscle mass and functional performance during aging. The greatest benefits were found among physically active adults who consumed higher amounts of dietary protein on a regular basis.Support or Funding InformationNational Heart, Lung and Blood Institute's Framingham Heart Study (Contract No. HHSN268201500001I).National Dairy Council