The Great Protein Debate: Do You Need Meat to Get Swole?
- M.R. Grigsby
- Jul 2
- 5 min read
Michael R. Grigsby, July 2, 2025, 9 am EST
Somerset, Kentucky- If you've ever wondered whether a vegan diet is good enough to support muscle growth—especially after lifting weights—new research has an answer that might surprise you.
The relationship between dietary protein source and muscle growth has been a longstanding topic of debate, especially within the context of plant-based versus omnivorous nutrition. Recent research has added to this discourse by investigating whether a vegan diet can support muscle protein synthesis (MPS) to the same extent as an omnivorous diet following resistance training. A randomized controlled trial (RCT) conducted by Monteyne et al. (2024) offers preliminary evidence suggesting that, under controlled conditions, a vegan diet may be equally effective in stimulating MPS as an omnivorous one, at least over the short term.
In this study, 40 healthy, resistance-trained young adults (mean age ~25) were assigned to either a vegan or omnivorous diet for 9 days. Both groups consumed protein in the range of 1.1–1.2 grams per kilogram of body weight per day, a value close to the Recommended Dietary Allowance (RDA) for sedentary individuals but arguably low for optimal hypertrophy in active populations. Participants also engaged in thrice-weekly resistance training. The study employed a 2x2 factorial design, evaluating not only diet type but also the temporal distribution of protein intake—either unbalanced (with the majority of protein consumed at dinner) or balanced (withprotein equally distributed across five meals).
Key Findings and Their Interpretation
The primary finding was that neither the protein source (plant-based vs. mixed animal-plant) nor the distribution pattern had a statistically significant effect on MPS. This suggests that, when total daily protein intake is held constant and the diet includes complementary plant proteins (e.g., soy, legumes, grains), vegan diets can elicit similar anabolic responses to those containing animal-derived proteins (Monteyne et al., 2024).
However, while these findings are encouraging for proponents of plant-based nutrition, several methodological and interpretive caveats warrant attention. First, the study's short duration (9 days) is insufficient to assess long-term outcomes such as changes in lean body mass, muscle fiber hypertrophy, or functional strength. MPS is a dynamic and transient process; acute increases in MPS do not necessarily translate to chronic muscle hypertrophy without sustained training and nutritional adequacy over weeks or months (Phillips & Van Loon, 2011).
Second, the relatively low protein intake (1.1–1.2 g/kg/day) may limit the generalizability of these findings to athletes or serious lifters who often require higher protein intakes (1.6–2.2 g/kg/day) to optimize hypertrophic outcomes (Morton et al., 2018). While this protein level may suffice for general health or novice trainees, it is unlikely to meet the demands of rigorous training regimens where the anabolic threshold is elevated.
Third, while the study ensured that the vegan diets were complete in essential amino acids (EAAs), this was achieved through controlled dietary planning and supplementation with soy and other complementary proteins, which may not reflect the average dietary habits of vegans. Many plant-based proteins are limited in one or more EAAs (notably lysine or methionine), and their digestibility and bioavailability are generally lower than those of animal proteins (FAO, 2013). This means that careful dietary planning is essential for vegans to meet anabolic needs—something not always practiced in real-world settings.
Moreover, the finding that protein timing (balanced vs. unbalanced) had no significant effect contradicts earlier mechanistic studies suggesting that spreading protein intake evenly throughout the day maximizes MPS by mitigating the “muscle full” effect (Areta et al., 2013). This discrepancy may stem from the short trial duration or the participants' total protein intake being near the lower end of optimal thresholds. It is possible that at higher protein intakes or over longer durations, distribution may exert a more noticeable influence.
Conclusions and Future Directions
While this study offers promising evidence that vegan diets can support acute muscle protein synthesis on par with omnivorous diets, it is far from definitive. The short duration, relatively low protein intake, and highly controlled dietary context limit its external validity. More research is needed to evaluate long-term hypertrophic adaptations, particularly in populations with higher training volumes or differing baseline diets.
Additionally, future studies should examine the real-world efficacy of self-selected vegan diets without controlled interventions to determine how often average plant-based eaters meet amino acid and protein quality benchmarks. Investigations incorporating diverse populations, more extended training periods, and higher protein intakes will provide a more comprehensive picture.
In summary, total daily protein intake appears to be a primary driver of MPS, and with sufficient planning, vegan diets can fulfill this role. However, assumptions of equivalency between plant and animal proteins must be tempered by an understanding of amino acid composition, digestibility, and practical dietary habits.
References:
Askow, A. T., Barnes, T. M., Zupancic, Z., Deutz, M. T., Paulussen, K. J. M., McKenna, C. F., Salvador, A. F., Ulanov, A. V., Paluska, S. A., Willard, J. W., Petruzzello, S. J., & Burd, N. A. (2025). Impact of Vegan Diets on Resistance Exercise-Mediated Myofibrillar Protein Synthesis in Healthy Young Males and Females: A Randomized Controlled Trial. Medicine and science in sports and exercise, 10.1249/MSS.0000000000003725. Advance online publication. https://doi.org/10.1249/MSS.0000000000003725
Areta, J. L., Burke, L. M., Ross, M. L., Camera, D. M., West, D. W. D., Broad, E. M., ... & Coffey, V. G. (2013). Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. The Journal of Physiology, 591(9), 2319–2331. https://doi.org/10.1113/jphysiol.2012.244897
FAO. (2013). Dietary protein quality evaluation in human nutrition (FAO Food and Nutrition Paper 92). Food and Agriculture Organization of the United Nations. https://www.fao.org/3/i3124e/i3124e.pdf
Monteyne, A. J., Wiles, R., Wust, R. C. I., Greig, C. A., Smith, K., & Phillips, B. E. (2024). Equivalent muscle protein synthesis following resistance exercise in healthy young adults consuming vegan or omnivorous diets. American Journal of Clinical Nutrition, 119(4), 854–865. https://doi.org/10.1016/j.ajcnut.2024.03.008
Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., ... & Phillips, S. M. (2018). 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. British Journal of Sports Medicine, 52(6), 376–384. https://doi.org/10.1136/bjsports-2017-097608
Phillips, S. M., & Van Loon, L. J. C. (2011). Dietary protein for athletes: From requirements to metabolic advantage. Applied Physiology, Nutrition, and Metabolism, 36(5), 647–657. https://doi.org/10.1139/h11-078
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This article was written by Michael R. Grigsby, one of the news editors for LCTI, LLC. Michael is passionate about the outdoors, photography, combat sports, bodybuilding, and powerlifting. He provides accurate and insightful news reports on a wide range of topics. He loves connecting with readers and is always happy to answer any questions you may have. Comments can be posted here (requires account login) or by sending an email to LCTILLC@outlook.com
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