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Plant Protein vs Whey for Building Muscle

8 min read

Plant-based eating has gone mainstream, and a familiar worry comes with it. Many people assume you cannot build real muscle without meat, eggs, or a tub of whey. The gym-floor belief is that animal protein rules and plant protein is a weak stand-in. The concern is fair, because the two proteins are not identical.

The honest answer from controlled trials is more reassuring. When total protein is high enough, plant eaters build as much muscle and strength as meat eaters. Whey has a small lead in the hour after a meal, and it fades once the day's protein adds up. Here is what the research shows, and how to get plant protein right.

1.2 kg
Leg lean mass gained on both a vegan and an omnivorous diet over 12 weeks, with no significant difference between them.
Hevia-Larrain 2021, protein-matched young men in resistance training
1.6 g/kg
Daily protein both groups reached, matched between the diets
Hevia-Larrain 2021, Sports Medicine
16
Trials in the meta-analysis found no effect of protein source on absolute muscle or strength gains
Lim 2021 meta-analysis, Nutrients
30 g
Plant-blend dose that matched whey for muscle protein synthesis
Govindasamy 2025 review, about 2.5 g leucine
24
Studies reviewed on plant protein and muscle recovery
Govindasamy 2025, Nutrients

What the trials actually found

The cleanest test comes from a 2021 trial published in Sports Medicine. Researchers took 19 long-term vegans and 19 omnivores, all young men, and put them through the same supervised resistance programme twice a week for 12 weeks. Both groups topped up their protein to 1.6 g per kg of body weight each day. The vegans used soy protein, the omnivores used whey.

The muscle results tracked closely. Leg lean mass rose by 1.2 kg in each group, and muscle cross-sectional area and fibre size grew in both. Leg-press strength rose by 97 kg in the vegans and 117 kg in the omnivores. That strength gap looks wide, but it was not statistically significant, and no other measure separated the two groups either. The authors concluded that a plant-based diet with enough protein supported muscle and strength gains similar to a protein-matched mixed diet.

Leg-press strength gained in 12 weeksKilograms added to one-rep max. Difference not statistically significant.+97 kg+117 kgVegan (soy)Omnivore (whey)

Source: Hevia-Larrain et al. 2021, Sports Medicine. 19 vegans and 19 omnivores, 12 weeks.

One trial is a signal, not a verdict. A 2021 meta-analysis in Nutrients pooled the wider evidence. The authors screened 3,081 papers and combined 16 randomised trials that compared animal and plant protein during training. Protein source did not change the amount of lean mass or strength gained. Animal protein held a small edge on one measure only, the percentage of body weight made up of lean tissue, and that edge was clearest in adults under 50. Across the trials, protein intakes sat above the recommended daily amount, which reflects how most people who train actually eat.

Why whey keeps a small head start

Plant and animal proteins are not twins. A 2015 review in the Journal of Nutrition laid out why a plant meal tends to drive a smaller rise in muscle protein synthesis in the hour or two after eating. Plant proteins carry less leucine, the amino acid that acts as the main trigger for building muscle. They also tend to be lower in one or two essential amino acids, and more of their amino acids get stripped out by the gut and liver before they reach the bloodstream.

That is a real difference, and it is also a small one. The post-meal spike is a short window, not the whole day. Muscle is built over weeks of repeated meals and training, so a slightly lower response to one serving matters far less than whether the week adds up to enough protein and enough hard sets. The 2015 review pointed to the fix as well as the problem. Its authors suggested eating more plant protein and combining sources, which is where the practical steps below start.

How plant protein closes the gap

A 2025 systematic review in Nutrients looked at 24 studies, 22 of them randomised trials, on plant protein and muscle recovery. The pattern was clear. A single plant source on its own, taken in a small dose, lagged behind whey for the acute response. A well-made blend did not. Combinations such as pea, rice and canola matched whey for muscle protein synthesis once the serving reached about 30 g with roughly 2.5 g of leucine.

The reviewers were careful about the limits. Many of the studies were small and carried a moderate to high risk of bias, and the trials varied too much to pool into a single number. Even so, the direction lines up with the longer training studies. Give plant protein a big enough serving, blend the sources, and the small edge that whey holds on a single scoop stops showing up in the muscle you build over months.

Leg lean mass gained in 12 weeksKilograms of lean tissue added. The two diets came out level.Vegan (soy)Omnivore (whey)+1.2 kg+1.2 kg01.5 kg scale

Source: Hevia-Larrain et al. 2021, Sports Medicine. No significant difference between diets.

How to build muscle on plant protein

The trials turn into four practical habits. None of them needs an animal product.

1. Hit your daily total first
Aim for roughly 1.6 g of protein per kg of body weight each day, the amount used in the trials. For a 70 kg person that is about 112 g. The daily total matters more than any single meal.
2. Make servings bigger
A plant serving of about 30 g of protein closes most of the gap with whey. Smaller plant servings fall short, so do not snack your way to the target in 10 g pieces.
3. Blend your sources
Mixing sources, such as pea and rice, fills the gaps in each one and raises leucine. A pea, rice and canola blend matched whey for muscle protein synthesis in the 2025 review.
4. Lean on higher-leucine plants
Soy foods such as tofu, tempeh and edamame lead on leucine, with lentils, beans and peas close behind. All carry more leucine than most grains, and the NHS lists beans, pulses and soy among the main protein foods to build meals around.

Common mistakes

  • Judging a protein by one scoop. The acute rise is a short window, and the day's total is what tracks with the muscle you build over months.
  • Relying on a single low-leucine source such as one grain or one nut, instead of a blend or a soy base.
  • Taking plant protein in servings too small to matter. Many trials that favoured whey used modest plant doses, not the 30 g that levels it with whey.
  • Chasing the perfect protein while under-training. Progressive, hard resistance training is the real driver, and any adequate protein supports it.

Frequently asked questions

Can you build muscle on a fully plant-based diet?
Yes. In the 2021 Sports Medicine trial, vegan men matched omnivores for muscle and strength gains over 12 weeks when both hit 1.6 g of protein per kg a day, with no significant difference between the groups. The key was total protein, not the source.
Is whey better than plant protein for muscle?
Whey drives a slightly larger spike in muscle protein synthesis after a single serving, because it is higher in leucine and well digested. Across training studies that edge does not translate into more muscle once total protein is adequate.
How much protein do I need to build muscle?
Most evidence points to roughly 1.6 g per kg of body weight a day for people training hard. That is about 112 g for a 70 kg adult. The NHS notes most people in the UK already eat enough protein for general health, but a muscle-building target sits higher.
Which plant proteins are best?
Soy and pea stand out for their amino acid profile, and a pea, rice and canola blend performed on par with whey in the 2025 review. Whole foods such as lentils, beans, tofu and tempeh round out the rest of the day's protein.
Do I need protein straight after training?
No urgent window exists for most lifters. Spreading protein across the day and reaching your total is what the evidence supports, so plant eaters do not need to rush a shake within minutes of finishing.

Bottom line

Plant protein can build as much muscle and strength as whey, as long as the total protein is high enough and the servings are big enough. Whey holds a small advantage in the hour after a meal, and that lead all but disappears across weeks of training. Hit your daily target, make plant servings around 30 g, blend your sources, and lean on soy, pulses and tofu. The muscle follows the training and the total, not the label on the tub.

Train with evidence on your side
DT Fitness London builds strength and nutrition plans around what the research supports, whether you eat plants, meat, or both. Book a consultation at www.dtfitnesslondon.com to get a plan matched to your training and your plate.

Sources

  • Hevia-Larrain V, et al. High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet to Support Resistance Training Adaptations. Sports Medicine 2021. pubmed.ncbi.nlm.nih.gov/33599941
  • Lim MT, et al. Animal Protein versus Plant Protein in Supporting Lean Mass and Muscle Strength: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients 2021. pmc.ncbi.nlm.nih.gov/articles/PMC7926405
  • Govindasamy K, et al. Effect of Plant-Based Proteins on Recovery from Resistance Exercise-Induced Muscle Damage. Nutrients 2025. pubmed.ncbi.nlm.nih.gov/40806155
  • van Vliet S, et al. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. Journal of Nutrition 2015. pubmed.ncbi.nlm.nih.gov/26224750
  • NHS. Eating a balanced diet. nhs.uk/live-well/eat-well
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