There’s an ongoing debate about which is better for muscle gains: plant or animal protein. Protein influences sarcopenia, the age-related loss of muscle mass. So the question is, can you build the same amount of muscle with a plant-based diet as an animal-based one?
“Yes, you just have to do a bit more legwork,” said Dr. Layne Norton, PhD in nutritional sciences and champion powerlifter.
Sarcopenia and Protein
Sarcopenia can start as early as the thirties and, unless mitigated by weight training and adequate protein intake, can worsen significantly.
People who are stronger and have more muscle mass as they age live longer, have less disease, and have a better overall quality of life.
—Dr. Layne Norton
A meta-analysis of randomized controlled trials that compares plant vs. animal protein in muscle health for young and older adults followed the following strict inclusion criteria: (1)
- Minimum of four weeks duration
- Participants were free of chronic illness
- Isocaloric diets
- Matched protein doses (within five grams)
These controls ensured that the only significant variable was the protein source.
Animal Proteins Win…Slightly
“Animal protein saw better results,” Dr. Norton said, but “It was not a massive difference.” Muscle retention and gains were marginally superior with animal protein. Strength and performance gains were not different between the two groups.
Four prominent studies reveal similar muscle growth from plant and animal protein intakes. (2)(3)(4)(5)
Bioavailability is how well the body can digest and use a protein. Animal proteins like eggs, beef, and chicken tend to be more bioavailable and have a better amino acid profile, especially leucine, which is critical for muscle protein synthesis.
Plant Proteins
While whole legumes and soybeans tend to be less digestible, isolated plant proteins, like soy protein isolate, are more complete.
“Soy has a relatively similar leucine content to sources of animal protein…around 8%,” said Dr. Norton. Its PDCAAS* score is 1.0, like whey protein,” Dr. Norton explained.
*Protein Digestibility-Corrected Amino Acid Score
The challenge with many plant proteins is that they’re often limited in one or more essential amino acids (EAAs). Combining complementary plant proteins, such as soy or pea protein supplements, may be a solution.
These are quality plant proteins based on PDCAAS, meaning you could consume them solely.
- Tofu — 93%
- Pea — 89-93%
- Soy protein isolate — 90%
- Quinoa — 92%
Why Elderly Adults May Need Animal Protein
Due to the amino acid differences, protein quality matters more at lower intake levels. “From 0.8 to 1.2 g per kilogram of body weight, protein quality is important,” Dr. Norton explained, especially for elderly individuals who often eat less.
Higher protein intakes (1.6+ g/kg) and protein type are less necessary since adequate total amino acid intake is already met for hypertrophy. (6)(7)
You can still build muscle with plant protein. You just have to be more targeted.
—Dr. Layne Norton
In other words:
- Animal protein is more efficient at lower doses.
- Plant protein works, but may require blends or higher doses.
- Isolated plant proteins like pea, soy, and quinoa can be nearly as effective as whey.
Whether you prefer plant or animal proteins, science suggests that either is sufficient for muscle retention and growth if consumed in adequate doses.
More In Nutrition
- How to Identify Protein Quality
- Mini Cuts — The Short-Term Diet for Long-Term Muscle Gain
- Does Dietary Fiber Combat Hypertension?
References
- Reid-McCann RJ, Brennan SF, Ward NA, Logan D, McKinley MC, McEvoy CT. Effect of Plant Versus Animal Protein on Muscle Mass, Strength, Physical Performance, and Sarcopenia: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Nutr Rev. 2025 Jul 1;83(7):e1581-e1603. doi: 10.1093/nutrit/nuae200. PMID: 39813010; PMCID: PMC12166177.
- Monteyne AJ, Coelho MOC, Murton AJ, Abdelrahman DR, Blackwell JR, Koscien CP, Knapp KM, Fulford J, Finnigan TJA, Dirks ML, Stephens FB, Wall BT. Vegan and Omnivorous High Protein Diets Support Comparable Daily Myofibrillar Protein Synthesis Rates and Skeletal Muscle Hypertrophy in Young Adults. J Nutr. 2023 Jun;153(6):1680-1695. doi: 10.1016/j.tjnut.2023.02.023. Epub 2023 Feb 22. PMID: 36822394; PMCID: PMC10308267.
- Askow AT, Barnes TM, Zupancic Z, Deutz MT, Paulussen KJM, McKenna CF, Salvador AF, Ulanov AV, Paluska SA, Willard JW, Petruzzello SJ, Burd NA. Impact of Vegan Diets on Resistance Exercise-Mediated Myofibrillar Protein Synthesis in Healthy Young Males and Females: A Randomized Controlled Trial. Med Sci Sports Exerc. 2025 Apr 4. doi: 10.1249/MSS.0000000000003725. Epub ahead of print. PMID: 40197715.
- Monteyne AJ, Dunlop MV, Machin DJ, Coelho MOC, Pavis GF, Porter C, Murton AJ, Abdelrahman DR, Dirks ML, Stephens FB, Wall BT. A mycoprotein-based high-protein vegan diet supports equivalent daily myofibrillar protein synthesis rates compared with an isonitrogenous omnivorous diet in older adults: a randomised controlled trial. Br J Nutr. 2021 Sep 14;126(5):674-684. doi: 10.1017/S0007114520004481. Epub 2020 Nov 11. PMID: 33172506; PMCID: PMC8110608.
- Hevia-Larraín V, Gualano B, Longobardi I, Gil S, Fernandes AL, Costa LAR, Pereira RMR, Artioli GG, Phillips SM, Roschel H. High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet to Support Resistance Training Adaptations: A Comparison Between Habitual Vegans and Omnivores. Sports Med. 2021 Jun;51(6):1317-1330. doi: 10.1007/s40279-021-01434-9. Epub 2021 Feb 18. PMID: 33599941.
- Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, Helms E, Aragon AA, Devries MC, Banfield L, Krieger JW, Phillips SM. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018 Mar;52(6):376-384. doi: 10.1136/bjsports-2017-097608. Epub 2017 Jul 11. Erratum in: Br J Sports Med. 2020 Oct;54(19):e7. doi: 10.1136/bjsports-2017-097608corr1. PMID: 28698222; PMCID: PMC5867436.
- Nunes EA, Colenso-Semple L, McKellar SR, Yau T, Ali MU, Fitzpatrick-Lewis D, Sherifali D, Gaudichon C, Tomé D, Atherton PJ, Robles MC, Naranjo-Modad S, Braun M, Landi F, Phillips SM. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. J Cachexia Sarcopenia Muscle. 2022 Apr;13(2):795-810. doi: 10.1002/jcsm.12922. Epub 2022 Feb 20. PMID: 35187864; PMCID: PMC8978023.
Featured image: @lewfitness on Instagram
