Plant protein holds its own against animal protein for muscle after 50

As people move through their fifties and beyond, holding on to muscle, strength and metabolic health becomes a central concern, and protein intake sits at the heart of that. Plant-based eating is growing fast, yet a persistent belief holds that animal protein is superior for maintaining lean mass and strength in older adults. Direct comparisons between plant-derived and animal-derived protein in this age group have produced inconsistent results, so this review set out to pool every randomised trial that pitted the two sources against each other in adults aged 50 and over.

The authors searched PubMed, Scopus, Google Scholar and ClinicalTrials.gov for randomised controlled trials published between January 2000 and August 2025 that directly compared plant and animal protein interventions lasting more than a month in adults aged 50 or older. Twenty-nine trials with 2,363 participants qualified, 61.3% of them women, with 1,174 people assigned to animal protein and 1,189 to plant protein. Notably, 25 of the 29 trials used soy as the plant source, and 23 of 29 tested purified isolates rather than whole foods. Seven trials added an exercise programme, and the team ran exploratory subgroup analyses by protein dose, duration, sex and exercise.

The headline result is a series of non-differences. Pooled analyses showed no significant gap between plant and animal protein on body composition, including lean mass and handgrip strength, or on most blood measures. The one exception was total cholesterol, where plant protein held a marginal advantage, though the studies disagreed with each other substantially on this point. Exploratory analyses hinted the cholesterol benefit appeared mainly at lower protein intakes and in trials without exercise, while diastolic blood pressure slightly favoured animal protein in one subgroup; the authors treat all of these secondary findings with caution.

This pooled analysis strengthens a growing case that protein source matters less than protein adequacy for adults over 50, at least across the durations trials have tested. It complicates the common assumption that animal protein is essential for preserving muscle in later life. The major caveat is what was actually compared: mostly soy isolates against dairy-derived proteins, not lentils against steak, and the authors explicitly warn against reading the result as proof that whole-food swaps are equivalent. Trials of diverse whole protein foods within well characterised, calorie-matched diets are the obvious next step.

If you are over 50 and get a meaningful share of your protein from plants, this is evidence that you are not automatically shortchanging your muscles or strength compared with someone eating animal protein. It is also a small point in favour of plant protein for total cholesterol, though that finding was marginal and inconsistent across studies. What it cannot tell you is how whole foods compare, since most trials used soy powders against dairy powders, or whether the picture changes over many years rather than the few months most trials lasted.