Plant Protein in Sports: What 12-Week RCT Data Show on Strength, Endurance, and Muscle Growth

Plant protein does not build muscle. That belief is stubborn in athlete circles, sometimes stated openly, more often dressed up as "plant proteins are inferior" or "vegans need to eat a lot more to catch up." The data from the past decade says otherwise. Yes, plant protein can support strength and muscle gains just as well as animal protein, provided the dose is there.

One 12-week RCT and two systematic reviews land on the same conclusion: when protein intake is matched, there is no measurable difference in muscle mass, strength, or body composition between vegan and omnivorous diets. The caveat, spelled out in every one of these papers, is simple. The protein dose has to be there.^1,2

For plant-based athletes, that means something concrete. Nothing more, nothing less. What the studies actually show, where the real nutrient gaps sit, and what all of this means for your training is what we unpack here.

Plant protein in sports: no difference at sufficient protein intake?

At a controlled intake of at least 1.6 g of protein per kg of body weight, sports medicine finds no measurable performance disadvantage for plant-based athletes.^1,2 That holds for resistance training and muscle growth. The endurance evidence is thinner but points the same way.

In everyday life, vegan athletes underestimate their protein intake more often than omnivores. 80 kg of body weight at 1.6 g/kg is 128 g of protein per day. Doable on a plant-based plan, but it takes more planning than a chicken sandwich. The difference is not in the biochemistry. It sits in the day-to-day logistics.

The core pattern holds: once study protein is matched, the between-group difference disappears. Consistently. Across different study designs and populations.

The 12-week study: vegans vs. omnivores in a direct resistance-training comparison

Hevia-Larraín et al. (2021) is the strongest direct evidence on this question to date.¹ Published in Sports Medicine, the study put 38 young men through 12 weeks of progressive resistance training. 19 were vegan, 19 were omnivorous, all had prior lifting experience. The decisive detail: both groups were fed exactly 1.6 g of protein per kg of body weight per day. No deviation, no adjustments.

Muscle protein synthesis responds to amino acids, and especially to leucine, not to where they come from. If a pea-and-fava blend clears the 2.5 g leucine threshold per meal, it activates mTOR (the intracellular signaling pathway for muscle growth) just as reliably as chicken breast. How leucine flips that switch is covered in our article "Leucine: The Switch for Muscle Growth".

One honest caveat. Hevia-Larraín et al. studied 38 young, trained men under laboratory conditions with tightly controlled diets. Older athletes, women, and recreational lifters with variable training are still missing from comparable RCTs. The findings are robust for the population studied and nothing beyond that.

What systematic reviews show on vegan athletic performance

Craddock et al. (2016) pooled 7 RCTs and one cross-sectional study.² The result: no meaningful performance differences between plant-based and omnivorous diets on endurance, strength, or body composition. The paper puts it plainly: a plant-based diet does not enhance athletic performance, but it does not compromise it either. Almost too tidy to be interesting. Caveat: 7 RCTs is a thin base, and the study designs are heterogeneous. That is not enough for sweeping generalizations.

Lynch et al. (2018) sharpen the picture.³ Their Nutrients review confirms no disadvantage in strength, anaerobic output, or endurance at sufficient protein. But they name six nutrients where vegan athletes are systematically undersupplied. This is the gap that most vegan sports advice skips over: everyone talks about protein, while the actual weak points sit elsewhere. One caveat: this is a narrative review, not a systematic one. The study selection is not documented under a PRISMA protocol.

Muscle creatine is the fuel layer for explosive output and fast recovery between sets. Vegans do not take in exogenous creatine from meat or fish, which often leaves their muscle stores lower. Not because a plant-based diet weakens the body, but because the starting point is different.

Which nutrients vegan athletes need to keep an eye on

Lynch et al. (2018) flag six nutrients that vegan athletes should actively manage: vitamin B12, iron, zinc, calcium, vitamin D, and EPA/DHA.³ None of these gaps are unbridgeable, but they require awareness and, for several of them, targeted supplementation.

Kaviani et al. (2020) deepen the creatine piece with their own systematic review that draws on 9 studies.⁵ The finding: vegan athletes respond more strongly to creatine supplementation than omnivores, because starting with lower muscle creatine levels simply leaves more headroom.

Creatine is the one supplement where current evidence shows a stronger effect in vegan athletes than in omnivores. That puts it at the top of the priority list, even ahead of protein supplements.

Why protein dose matters more than protein source

The evidence is consistent: the single strongest factor for muscle mass and strength gains is total daily protein intake.^1,2 Not timing, not a quality score, not the source. The source comes after.

Are you lifting regularly, sleeping enough, and hitting 1.6 g/kg per day? Then the protein source is a matter of taste, not physiology. How to calculate your actual requirement is covered in "Vegan Muscle Building: Nutrition and Protein".

Running intense training weeks and eating in a calorie deficit? Rogerson (2017) and others suggest going up to 2.0 g/kg to protect muscle mass.⁴ That applies to every athlete. A plant-based diet changes nothing about that, except that you need a bit more planning to hit the number.

Plant protein compared to whey: if a high-quality pea-and-fava blend gives you enough leucine and essential amino acids, you are biochemically on equal footing. The full comparison with the research is here: Plant Protein vs. Whey.

One aspect that often gets lost in the vegan-sports conversation: protein quality is measurable. The DIAAS score (digestible indispensable amino acid score) rates how well a protein delivers the essential amino acids the body cannot make on its own. Pea-protein isolate scores better than most grain proteins, and a blend of pea plus rice or fava covers the amino acid profile almost completely. That is why formulation matters more for plant-based protein powder than for whey: the source and the mixing ratio decide whether you clear the 2.5 g leucine threshold per meal.

FAQ: plant protein in sports