Why Plant Protein Is More Effective Than Animal Protein For Muscle Growth

Sarcopenia and Protein

Sarcopenia can start from the age of thirty-three and, unless it is reduced by weight training and adequate protein intake, it can get worse.

People who are stronger and more muscular as they get older live longer, have less disease, and have a better quality of life.

—Dr. Layne Norton

A a meta-analysis of randomized controlled trials comparing plant and animal protein on muscle health in adults and the elderly followed the following strict guidelines: (1)

• A minimum of four weeks
• Participants did not have any chronic illness
• Isocaloric Diets
• The amount of protein has been compareds (within five grams)

These controls ensured that the only significant variable was protein source.

Animal Protein Wins…Slightly

“Animal proteins have seen better results,” said Dr. Norton, but “it wasn’t a big difference.” Muscle retention and gain was slightly higher than animal protein. Strength and performance gains were not different between the two groups.

Four prominent studies reveal similar muscle growth from plant and animal proteins. (2)(3)(4)(5)

Bioavailability is how well the body can digest and use protein. Animal proteins such as eggs, beef, and chicken tend to be more bioavailable and have a better amino acid profile, especially leucine, which is very important for muscle protein synthesis.

Plant Proteins

While whole grains and soybeans are often indigestible, isolated plant proteins, such as soy protein isolate, are more complete.

“Soy has the same leucine content as animal protein sources…about 8%,” said Dr. Norton. Its PDCAAS* score is 1.0, just like whey protein,” explains Dr. Norton.

*Protein Digestibility-Adjusted Amino Acid Ratio

The challenge with most plant proteins is that they are often limited to one or more amino acids (EAAs). Adding complementary plant proteins, such as soy or pea protein supplements, can be a solution.

These are quality plant proteins derived from PDCAAS, which means you can only eat them.

• Tofu – 93%
• Peas – 89-93%
• Soy protein separates – 90%
• Quinoa – 92%

Why Older People May Need Animal Protein

Because of the amino acid differences, protein quality is more important at lower levels of the diet. “From 0.8 to 1.2 g per kilogram of body weight, the quality of protein is important,” Dr. Norton explained, especially for older people who tend to eat less.

A very high protein (1.6+ g/kg) and type of protein is not needed as much as an adequate amount of amino acid absorption has been met with hypertrophy. (6) (7)

You can still build muscle with plant proteins. You just have to be very focused.

—Dr. Layne Norton

In other words:

• Animal proteins works well at low doses.
• Plant proteins it works, but may require combinations or higher doses.
• Isolated plant proteins like peas, soy, and quinoa can be almost as effective as whey.

Whether you choose plant or animal protein, science suggests that either is sufficient for maintaining muscle mass and growth when consumed in adequate amounts.

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References

1. 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.
2. 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 Comparison of 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.
3. Askow AT, Barnes TM, Zupancic Z, Deutz MT, Paulussen KJM, McKenna CF, Salvador AF, Ulanov AV, Paluska SA, Willard JW, Petruzzello SJ, Burd NA. Effect of a Vegan Diet 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. Policy number: 40197715.
4. 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 levels of daily myofibrillar protein synthesis compared to an isonitrogenous omnivorous diet in older adults: a randomized controlled trial. Mr J Nutr. 2021 Sep 14;126(5):674-684. doi: 10.1017/S0007114520004481. Epub 2020 Nov 11. PMID: 33172506; PMCID: PMC8110608.
5. Hevia-Larraín V, Gualano B, Longobardi I, Gil S, Fernandes AL, Costa LAR, Pereira RMR, Artioli GG, Phillips SM, Roschel H. A High-Protein Plant-based Diet Versus a Protein-Matched Omnivorous Diet to Support Adaptation to Resistance Training in Normal Conditions: Compari Sports Med. 2021 Jun;51(6):1317-1330. doi: 10.1007/s40279-021-01434-9. Epub 2021 Feb 18. PMID: 33599941.
6. 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 gains in muscle strength and power 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. October 2020; 54(19):e7. doi: 10.1136/bjsports-2017-097608corr1. PMID: 28698222; PMCID: PMC5867436.
7. 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. A systematic review and meta-analysis of protein intake to support muscle mass and performance 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