Strength

Vegan diets build as much muscle as diets with meat

By WhyStopHarmingAnimals.com

When protein intake is matched, people eating vegan diets build the same muscle as people eating meat, eggs and dairy[1][2][3][5][6][8]. That result holds in young adults and in older adults, in people new to the diet and in people who have been vegan for years, and in trials that measure everything from the rate muscle protein is built to thigh volume on an MRI scan[1].

The trials that measured muscle directly

The most thorough test so far comes from Monteyne and colleagues in the UK, published in the Journal of Nutrition in 2023[1]. They first used stable isotopes to measure daily muscle-protein synthesis on a high-protein vegan diet built around mycoprotein and on an omnivorous diet, both at about 1.8 g of protein per kilogram of body weight[1]. The rates matched[1], at rest and after exercise. Then 22 young adults lifted five times a week for 10 weeks, eating about 2 g/kg[1]. Lean mass rose 2.6 kg on the omnivorous diet and 3.1 kg on the vegan one[1]. Thigh muscle volume rose 8.3% in both groups[1], and muscle-fiber area grew by about a third in both[1]. Strength on multiple lifts rose by comparable amounts[1]. Every one of those outcomes came from DXA scans, MRI, muscle biopsies or 1-rep-max tests[1].

In Brazil, Hevia-Larraín and colleagues (Sports Medicine, 2021) asked what happens in people who have been vegan for a long time[2]. They compared 19 men who had eaten vegan for at least a year with 19 omnivores[2], with protein matched at 1.6 g/kg[2], through 12 weeks of supervised lifting twice a week[2]. Leg lean mass on DXA, muscle measured by ultrasound, biopsies and 1RM strength all increased similarly in the two groups[2]. Protein source was not what limited anyone’s gains[2].

At the University of Illinois, Andrew Askow, Nicholas Burd and colleagues randomized 40 young adults[3] to a vegan or an omnivorous diet (Medicine & Science in Sports & Exercise, 2025)[3][4]. Protein was set at a moderate 1.1–1.2 g/kg[3], much closer to what people actually eat than the doses in supplement ads. After a week on the diet, participants trained for nine days while drinking deuterium-labeled water, which lets researchers trace newly built muscle protein, and they gave leg-muscle biopsies at the start and end. Myofibrillar protein synthesis did not differ between the diets[3]. It also made no difference whether protein was spread evenly across the day’s meals, contrary to advice that grew out of single-meal experiments[3].

Older muscle builds on plants too

Muscle responds less readily to protein with age, so older adults are where a weakness in plant protein would show up first. Two randomized studies looked for it and found none[5][6]. In Monteyne’s 2020 trial in the British Journal of Nutrition, older adults ate either a high-protein vegan diet based on mycoprotein or an omnivorous diet with the same amount of protein, and daily myofibrillar protein synthesis was equivalent[5].

Domić and colleagues (Journal of Nutrition, 2024) fed physically active older men and women vegan or omnivorous diets at about 1.2 g of protein per kilogram, with calories and protein matched[6], and measured muscle-protein synthesis over 10 days[6]. It did not differ between the diets[6]. A carefully composed vegan menu did not weaken the muscle-building response in people whose muscles are already harder to build[6].

Pea protein against whey

Most protein powder on the market is whey, a by-product of the dairy industry. Babault and colleagues randomized 161 young men to pea protein, whey or a placebo during 12 weeks of resistance training (Journal of the International Society of Sports Nutrition, 2015)[7]. Biceps thickness rose 20.2% on pea protein, 15.6% on whey and 8.6% on the placebo[7]. Strength rose about 17% on both proteins[7].

Lim and colleagues reviewed the plant-versus-animal protein research in Nutrients in 2021[8]. Once total protein is matched, they found, plant proteins support gains in lean mass and strength comparably to animal proteins in resistance-training studies[8]. The edge for milk or meat that shows up in older research comes from acute tests of a single meal, which can’t tell you what a whole diet does over weeks of training[8].

What these trials cover

All of these are controlled studies with direct measurements[1][2][3][5][6][7], but they are short, from nine days to 12 weeks[1][2][3][6], and most are small. Babault’s trial, the largest, compared protein powders rather than whole diets[7]. Most of the trials matched protein at generous intakes, so what they show is that plant protein builds muscle when there is enough of it[8], which is the same condition that applies to animal protein. None of them found that meat, eggs or milk built muscle that plants could not[1][2][3][5][6][7][8].