This study aimed to examine the association between protein intake and risk of sarcopenia, with a specific focus on protein sources, in middle-aged and older adults.

This was a 9-year follow-up study. Dietary protein intake was assessed by a validated FFQ with energy adjustment using the residual method. Sarcopenia was defined by using height-adjusted appendicular lean mass and grip strength. Adjusted OR for sarcopenia were calculated by multivariable logistic regression analysis.

Baseline surveys (2011–2014) for the Murakami and Uonuma cohorts assessed body size, lifestyle and medical history. Sarcopenia-related measurements were conducted in 2021–2022 in Murakami, Sekikawa, Uonuma and Minamiuonuma, Japan.

6232 individuals aged 40–74 years (mean age, 62·4 years; females, 54·8 %).

An inverse association between plant protein intake and sarcopenia was observed in males (Pfor trend = 0·018), although total and animal protein intakes were not. Animal-to-plant protein ratio was U-shaped in its association with sarcopenia; adjusted OR for the lowest and highest quintiles of the ratio compared to the middle quintile were 1·71 (95 % CI: 0·96, 3·07) and 1·97 (95 % CI: 1·10, 3·53), respectively, for males (Pfor quadratic term = 0·017), and 1·93 (95 % CI: 1·06, 3·51) and 1·65 (95 % CI: 0·90, 3·05), respectively, for females (Pfor quadratic term = 0·010).

An imbalanced intake of plant and animal proteins may increase the risk of sarcopenia, highlighting the importance of balanced protein intake.