https://pubmed.ncbi.nlm.nih.gov/39813010/
Review pooled results from 30+ RCTs comparing plant and animal protein. It showed no meaningful difference in strength, performance, or muscle size. This was even more apparent when they compared soy protein vs animal protein. In the study the SMD (Standardized Mean Difference) which is just a way of measuring how big the difference is between groups. So a SMD of 0 = no difference at all and ~0.2 = very small difference. In this study they saw an overall difference of ~0.20 (nearly indistinguishable) and then soy vs animal was ~0.02 (essentially no measurable difference at all). The p-value tells you whether a difference is likely real or just random chance. If p < 0.05 = likely real difference - If p > 0.05 = no reliable difference. In this case they saw soy vs animal had a p = 0.80 - So completely indistinguishable. The already extremely small differences for animal protein disappear entirely when you use a high quality plant protein like soy or match protein intake properly.
https://pubmed.ncbi.nlm.nih.gov/33670701/
Across 16 RCTs, there was no difference in muscle strength and no meaningful difference in total muscle gained between plant and animal protein groups. The only difference observed was a small variation in the percentage of body mass made up of lean tissue. This does not necessarily mean more fat gain, but rather a slight shift in body composition ratios. Importantly, the size of this difference was very small and not practically meaningful (so if it was correlated to body fat % in a particular example, it would be extremely small, likely less than half lb difference). Basically, in the studies if one group gains slightly less fat, their % muscle goes up - that doesn’t mean they built more muscle it’s just math of their total body composition. So simply adjusting like total protein intake, calorie control, and food selection as needed are the main drivers of body composition. So even if a small difference appears in pooled data, it is fully explainable by diet composition variables rather than protein source itself, and can be adjusted for real world diet planning whether your goal is muscle gain, fat gain, or something else.
https://www.mdpi.com/2072-6643/16/16/2748
This review of 31 RCTs looked at strength, endurance, and muscle-building processes where plant protein clearly improves from baseline strength, performance, and hypertrophy - And when compared to animal protein there was no consistent advantage for it. Protein itself is what matters and plant protein works just as well when you get enough of it.
https://sportrxiv.org/index.php/server/preprint/view/526/version/676
MPS study (mechanistic-focused meta-analysis) analysis looked at ~10 studies focused on how the body builds muscle internally and found that plant protein can stimulate muscle-building just fine and any differences of any kind come from variances in leucine and digestibility. It’s not saying that plant protein is innately worse, it’s saying that some plant proteins have slightly less of the leucine muscle trigger amino acids or are absorbed a bit less efficiently. But if you eat enough protein overall or choose better plant sources the differences go away. This would only be applicable to someone who is doing everything in their power to fully maximize muscle growth. For the average person who just wants to be healthy, fit, and have a good muscular build, there’s no real reason to even take the time to worry about this as long as you’re getting enough protein in general for your goals.