Whey vs plant protein: can vegetarians build as much muscle?

The short answer

• 9trials

  Compared soy with whey and other animal proteins. Gains in strength and lean mass were about the same.

• 1.2kg

  Leg lean mass gained in 12 weeks by both vegans and meat-eaters on the same protein

• 0.4kg

  More lean mass with animal protein in adults under 50, in a review of 16 trials

• 30trials

  In the newest review: a small edge for animal protein on muscle size, none on strength

Key findingIf you eat enough protein and lift weights, soy and whey work about equally well. Other plant proteins and fully plant-based diets may build a little less muscle, so plan your protein with care.

What is the difference between whey and plant protein?

Whey is one of the two main proteins in milk. It is the liquid left over when paneer or cheese is made, dried into a powder. Plant protein comes from foods like dal, chana, rajma, soya, nuts, seeds and grains. Plant protein powders are usually made from soy, peas or rice.

Protein is made of 20 building blocks called amino acids. Nine of them must come from food. Animal proteins like whey have all nine in good amounts. Most plant foods are low in one or more. For example, grains are low in lysine and pulses are low in methionine. Eating grains and pulses together, like dal with rice or roti, fills the gaps.

Whey also has more leucine. Leucine is an amino acid that works like a switch for muscle building.

You can make up the difference by eating a little more. About 38 g of soy protein gives 3 g of leucine, the top of the panel’s advice for one meal.

Is plant protein better than whey?

Not better, but soy is about as good. This 2018 study was a meta-analysis: a study that pools the results of many earlier studies. People taking soy protein gained as much strength and lean mass as people taking whey, milk or beef protein. Lean mass is everything in your body except fat, including muscle.

One caution: the lead author runs a soy nutrition group that is partly funded by the soy industry. But other reviews, with no such links, found the same result for soy.

Rice protein has been tested less. In one 8-week trial, 24 trained young men took 48 g of whey or rice protein a day. Both groups gained lean mass and leg strength by similar amounts.

Plant protein vs animal protein: the bigger picture

Short lab tests often favour whey. In a 2021 review of 27 studies, higher-quality proteins like whey switched on muscle building 33–41% more over a few hours. But in training studies of 8 to 16 weeks, lean mass grew by about the same amount. Tests that last a few hours don’t always show what happens over months.

The newest review, from 2025, pooled 30 trials with 1,538 people. On average, animal protein led to slightly more muscle than plant protein. The edge was small, and it showed up mainly in adults under 60. Soy matched milk protein. The gap came from other plant proteins, such as rice, oat, potato and chia, and from plant-based diets. Strength was about the same.

A 2021 review put the gap in kilograms. In adults under 50, animal protein gave about 0.4 kg more lean mass than plant protein. Across all ages, the gap was 0.22 kg, which was not a clear difference. Strength gains were the same.

Can vegetarians and vegans build as much muscle?

Yes, if they eat enough protein. In this 2021 study, young vegan men built as much leg muscle as meat-eating men. Both groups ate 1.6 g of protein per kg of body weight a day. It was not a trial where people were put into groups by chance: the men had chosen their diets long before.

Whole plant-based diets need more care. The 2025 review included 7 trials of whole diets. People who switched to plant-based diets kept or built a little less muscle than people on diets with animal protein. Most of these were weight-loss diets in people with overweight, obesity or diabetes. Plant foods can also be harder to digest than protein powders, though soaking and cooking help.

How Indian vegetarians can get enough protein

India’s 2024 dietary guidelines show how a balanced vegetarian day adds up. Their model day has 2,000 calories (kcal) and about 72 g of protein.

72 g is about 1.1 g per kg for a 65 kg person (our calculation). That is above India’s RDA (recommended dietary allowance) of 0.83 g per kg. If you lift weights and aim for 1.6 g per kg, you need about 104 g. That is about 32 g more (our calculation).

• Keep the 3:1 rule. India’s guidelines suggest about 3 parts cereal to 1 part pulses (raw weight), plus about 250 ml of milk a day.
• Add soy. Soya chunks are about 56–59% protein by dry weight, and soy did as well as whey in trials.
• Use dairy if you eat it. Paneer, curd and milk add good-quality protein. See protein in paneer.
• Spread it out. Have some protein at each meal. See how much protein per meal.

If most of your protein comes from cereals, India’s experts advise 1 g per kg a day instead of 0.83.

Plant protein or whey protein powder: which should you choose?

You may not need a powder at all. India’s 2024 guidelines say most athletes can get enough protein from food. They call powders unnecessary for normal healthy life, and note that some contain added sugar and sweeteners.

If you use one, choose based on what you eat, what suits your stomach and what you can afford. Whey and soy both did well in trials. Rice, pea and other plant powders have less research, so a blend or a slightly bigger scoop is a sensible choice.

Supplement quality varies between brands. Talk to a doctor or pharmacist before you use protein powder if you are pregnant or breastfeeding. The same goes if you take medicines or have a health condition, such as kidney disease.

Claims and evidence

• ClaimPlant protein can’t build muscle.

  EvidenceSoy built as much strength and lean mass as whey and other animal proteins in 9 trials. Young vegan men gained as much leg muscle as meat-eaters on the same protein.

• ClaimWhey is far better than soy.

  EvidenceIn short lab tests whey switched on muscle building more. Over months of training, 17 trials found no difference in muscle between soy and milk protein.

• ClaimAll plant proteins are as good as soy.

  EvidenceOther plant proteins, such as rice, oat, potato and chia, did a little worse than animal protein in 5 trials. They have been studied much less.

• ClaimSoy’s plant oestrogens (natural chemicals that act a little like a hormone) stop muscle growth.

  EvidenceThat idea comes from mouse studies, one at a very high dose. In training trials, people taking soy gained as much as people taking animal protein.

What this means for you

What the research can’t tell you yet

• Most plant proteins. Most trials compared soy with milk proteins. Rice, pea and other plant proteins have only a handful of trials.
• Real meals. Most trials used protein powders. Whole plant foods may work differently.
• Who was studied. Most people were young men, often new to weights. The vegan study had only 38 men.
• Industry links. The lead author of the soy review is linked to a soy-funded group.

How Bodyvault uses this research

Bodyvault’s meal plans come in vegetarian, vegetarian-with-eggs, vegan and Jain versions. The app sizes each plan’s portions to your own calorie and protein targets. In Bodyvault Pro, if you ask Coach about your diet while your protein is running short, it suggests foods to add. On a vegetarian diet, it suggests paneer, tofu, dal, curd or a whey or soy shake, with no meat or egg ideas.

General information about fitness and nutrition, not medical advice. If you have a health condition, are pregnant or take medication, talk to your doctor before changing your diet or training.