# Association of the Dietary Plant-To-Animal Protein Intake Ratio with the Incidence of Slow Gait Speed in Older Adults

## TL;DR

This study found that the ratio of plant to animal protein in older adults' diets does not affect their risk of developing slow walking speed.

## Contribution

The study provides new evidence that higher plant protein intake does not compromise physical functioning in older adults.

## Key findings

- No significant association was found between the plant-to-animal protein ratio and incident slow gait speed.
- Higher plant-to-animal protein ratios showed a non-significant trend toward lower risk of slow gait speed in faster baseline walkers.
- A sustainable diet with more plant protein does not appear to harm physical functioning in older adults.

## Abstract

Although plant proteins have less environmental impact than animal proteins, it remains unclear whether they can adequately support physical functioning in old age.

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.

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.

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.

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.