Abstract
BACKGROUND: Although plant proteins have less environmental impact than animal proteins, it remains unclear whether they can adequately support physical functioning in old age. OBJECTIVE: This prospective study aimed to investigate the association of the dietary plant-to-animal protein intake ratio with the incidence of slow gait speed among older adults. METHODS: Data from 997 adults [50.7% male, mean age 65.5 (SD 6.9) y] with a baseline gait speed ≥0.8 m/s were derived from the Longitudinal Aging Study Amsterdam. The dietary plant-to-animal protein intake ratio was calculated from a 238-item food frequency questionnaire completed from 2014 to 2015. Gait speed was measured at baseline and at three 3-y follow-up waves using a 6-meter walk test. Cox proportional hazards models estimated the association between protein ratio quintiles and incident slow gait speed (<0.8 m/s), while adjusting for demographic and lifestyle factors and testing for interaction by sex, overall diet quality, protein intake, and baseline gait speed. RESULTS: The median dietary plant-to-animal protein intake ratio was 0.67 [interquartile range (IQR): 0.52 to 0.86]. During follow-up, slow gait speed (<0.8 m/s) developed in 415 participants (41.6%). No significant association was found between the protein ratio and incident slow gait speed. The adjusted hazard ratio of the highest (ratio > 0.91) compared with the lowest (ratio ≤ 0.49) quintile was 0.98 (95% confidence interval: 0.68, 1.42; trend across quintiles P = 0.89). No significant interactions were observed with sex, overall diet quality, or total protein intake. A higher plant-to-animal protein ratio was suggested to be associated with a lower risk of incident slow gait speed in those with relatively faster baseline gait speed, although associations were not statistically significant. CONCLUSIONS: Among Dutch older adults, the dietary plant-to-animal protein intake ratio was not associated with the risk of developing slow gait speed, suggesting that a more sustainable diet including higher plant protein intake may not compromise physical functioning in older adults.