Effects of Dietary Protein on Skeletal Muscle Mass and Sarcopenia Risk in Middle‐aged Framingham Adults

Sarcopenia, or age‐related muscle mass loss leads to impairment of physical function as well as increased mortality risk. The adequacy of the current protein RDA to counter progressive loss of muscle in older adults is under debate. Our goal was to examine the impact of dietary protein on skeletal muscle mass (SMM) and risk of sarcopenia in middle‐aged adults, using data from the prospective Framingham Offspring Study. Dietary data from 3‐day records in exams 3 and 5 for 1380 subjects free of cancer and congestive heart failure were used. Bioelectrical impedance analysis at exams 6 and 7 was used to calculate SMM. Sarcopenia was defined using Janssen's skeletal muscle mass equation. ANCOVA and multiple logistic regression models were used to control for confounding by age, sex, education, height, activity, smoking, and % fat calories. Mean weight‐adjusted protein residuals across tertiles of intake were 0.9, 1.2, and 1.5 grams/kg/day. Consuming more protein, alone or as part of a healthy diet (FV, fiber, whole grains), led to higher mean %SMM and lower risk of sarcopenia. Increasing total, animal, and plant protein intakes were linked with statistically significant increases in %SMM (1.2, 0.9, 1.4), respectively. Consuming more total, animal, or plant protein was associated with a 24% (95% CI: 0.62‐0.92), 22% (95% CI: 0.64‐0.94), and 24% (95% CI: 0.62‐0.93) reduced risk of sarcopenia, respectively. There was no modification of the effects of protein on sarcopenia risk by intakes of other dietary factors such as FV, fiber, or whole grains. In Framingham, higher dietary protein intakes lowered the long‐term risk of sarcopenia in middle‐aged adults.