Plant vs Animal Protein for Muscle

Feb 28

Written by INNER G

Plant protein versus animal protein is an argument that never seems to end. One side says plant protein isn’t good enough for building muscle. The other says a well planned plant based diet gives you every essential amino acid you need. This guide looks at how the two actually compare, food by food, what the research says about soy, and how to get the most out of whichever you eat.

How Much Protein Is in Common Foods

Protein numbers you see listed often mix dry and cooked weights. Dry lentils are about 25 g of protein per 100 g, but once they’re boiled they soak up water and come in at about 9 g. The chart below uses cooked or ready to eat values from the USDA’s FoodData Central database, so the foods are compared the way you’d actually eat them (USDA, 2019). Switch between protein and leucine to see both.

Green bars are plant foods and dark bars are animal foods. Source: USDA FoodData Central (SR Legacy). Tofu is firm tofu made with calcium sulfate; brands vary, and soft or regular tofu has about half the protein.

The Amino Acids That Matter Most

How useful a protein is for muscle depends mostly on its essential amino acids, the ones your body can’t make. Plant proteins contain all of them, but many are lower in leucine, lysine or methionine than animal proteins. A lab analysis of plant protein powders found essential amino acids made up about 21 to 22% of oat, lupin and wheat protein, compared with 43% for whey and 32% for egg. Methionine and lysine were also lower in the plant proteins on average (Gorissen et al., 2018).

Leucine is the main trigger for muscle protein synthesis, the process that repairs and builds muscle after training.
Lysine is often the lowest essential amino acid in grains.
Methionine is often the lowest in beans and lentils.

The fix is simple: mix your sources. Grains and legumes cover each other’s gaps, which is why pairings like lentils with rice or beans with quinoa work well. The same study found that blends of plant proteins, or plant and animal proteins together, can come close to the profile of animal protein (Gorissen et al., 2018).

Plant vs Animal Protein for Building Muscle

Right after a workout

In the hours after training, whey switches on muscle protein synthesis more than soy does. In one study of young men, whey raised it about 31% more than soy after a workout (Tang et al., 2009). Lower leucine, lower digestibility and a less complete amino acid profile are the likely reasons plant proteins tend to fall short in these short studies (van Vliet et al., 2015).

Over weeks of training

Over a full training program, the gap mostly closes. A meta analysis of nine studies with 266 people found soy protein led to the same gains in strength and lean mass as whey or other animal proteins (Messina et al., 2018). A larger meta analysis of 16 trials found no overall difference in lean mass or strength, though animal protein had a small edge for lean mass in some study groups (Lim et al., 2021). A 2025 review reached a similar conclusion: animal protein is still very effective, but well planned plant protein, especially blends, is a workable alternative (Pandey et al., 2025).

If you eat mostly or only plants, the practical answer is to eat a little more total protein and mix your sources (van Vliet et al., 2015). For how much protein to aim for each day, see how much protein you need for muscle and fat loss.

Try it: protein in a portion

Pick a food and enter how much you eat to see roughly how much protein and leucine you get. The numbers use the same USDA values as the chart above.

Food:

Amount (grams):

For reference, a palm sized piece of cooked chicken is often around 100 to 120 g, and a cup of cooked lentils is about 200 g. Weigh your own portions if you want an exact number.

The Soy Question

Soy is the plant protein people worry about most. The research on muscle is reassuring: in the training studies above, soy protein built strength and muscle as well as animal protein (Messina et al., 2018).

What about trypsin inhibitors?

Raw soybeans contain trypsin inhibitors, compounds that can get in the way of digesting protein. Cooking and fermenting deal with most of them:

Heat. In a study on soy milk, conventional heating lowered trypsin inhibitor activity from 10% in raw soybean to 3%, and made the protein about 11% more digestible (Vagadia et al., 2018).
Fermentation. A 2025 lab study found the fermentation that turns soybeans into tempeh breaks down protein and makes it easier to digest, at least in simulated digestion (Wu et al., 2025).

If soy is part of a varied diet and it’s cooked, as tofu, tempeh and soy milk are, trypsin inhibitors aren’t something to worry about.

Why tempeh is worth a try

Tempeh has about 20 g of protein per 100 g, close to salmon and well above cooked beans and lentils (USDA, 2019). It’s fermented, which makes it easier to digest, though it’s almost always cooked before you eat it, so don’t count on it for live probiotics.

Beyond Muscle: Fullness and Long Term Health

Fullness. Beans, lentils and chickpeas bring fibre along with their protein, which helps keep you full when you’re eating less to lose fat.
Heart health. In a study that followed more than 131,000 people for up to 32 years, people who got more of their protein from plants had a lower risk of dying from heart disease and from any cause (Song et al., 2016).
Meat. Eating more processed meat and unprocessed red meat has been linked to a slightly higher risk of heart disease, while fish was not (Zhong et al., 2020).

Both of those are observational studies, so they show links rather than proof of cause. They do suggest that swapping some processed and red meat for plant protein or fish is a reasonable move.

So Which One Is Better?

Neither wins outright. Animal protein gives you more leucine per bite and is easier to digest. Plant protein does the same job over time if you eat a little more of it and mix your sources, and it brings fibre with it. Soy and tempeh are solid choices for building muscle. The best protein is the one you’ll eat consistently, at every meal. If you’re eating mostly plants and training hard, see our guide to plant based diets and athletic performance.

Putting It Into Practice

If you’d like a coach to help you build meals around the protein you like to eat, here’s how we can help:

Nutrition coaching in Vaughan gives you a plan that fits how you eat, plant based or not, and a coach who checks in with you. It’s $100/month + HST on its own, and it’s usually included when you train one on one 2 to 3 times a week.
One on one personal training in Vaughan starts with a Crush It Session: about an hour with a coach. We'll credit your full $100 toward your first training package when you sign up within 48 hours after your session.
Prefer training in a group? Our small group classes are capped at 16 people, and you can try a week of unlimited classes with the $30 (+ HST) seven day trial. Join by day 5 and your $30 is credited toward your membership.

Questions? Call or text us at (289) 536-8066 or email g-squad@innerg.ca.

Frequently Asked Questions

Can you build muscle with plant protein?
Yes. Over weeks of training, studies find soy and other plant proteins lead to similar gains in strength and muscle as animal protein, especially when you eat enough total protein and mix your sources.

Is plant protein a complete protein?
Plant foods contain all the essential amino acids, but many are low in one or two, such as lysine in grains or methionine in legumes. Soy is the main exception. Eating a mix of plant proteins through the day covers the gaps.

Do I need more protein if I eat plant based?
Probably a little more. Plant proteins tend to be slightly less digestible and lower in leucine, so eating a bit more total protein helps make up the difference.

Is soy bad for you?
For most people, no. Cooking and fermenting remove most of the trypsin inhibitors in soy, and soy protein has built muscle as well as animal protein in training studies.

References

Messina M, Lynch H, Dickinson JM, Reed KE (2018). No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance Exercise. International Journal of Sport Nutrition and Exercise Metabolism, 28(6):674-685. PubMed
Lim MT, Pan BJ, Toh DWK, et al. (2021). Animal Protein versus Plant Protein in Supporting Lean Mass and Muscle Strength: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients, 13(2):661. PubMed
Pandey A, Pearlman M, Bonnes SL, Nour SI (2025). Can We Maintain Muscle Mass on a Plant-Based Diet? Current Nutrition Reports, 14(1):16. PubMed
Gorissen SHM, Crombag JJR, Senden JMG, et al. (2018). Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids, 50(12):1685-1695. PubMed
van Vliet S, Burd NA, van Loon LJ (2015). The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. The Journal of Nutrition, 145(9):1981-91. PubMed
Tang JE, Moore DR, Kujbida GW, et al. (2009). Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. Journal of Applied Physiology, 107(3):987-92. PubMed
Vagadia BH, Vanga SK, Singh A, et al. (2018). Comparison of Conventional and Microwave Treatment on Soymilk for Inactivation of Trypsin Inhibitors and In Vitro Protein Digestibility. Foods, 7(1):6. PubMed
Wu JY, Wee S, Ler SG, et al. (2025). Unraveling the impact of tempeh fermentation on protein nutrients: An in vitro proteomics and peptidomics approach. Food Chemistry, 474:143154. PubMed
Song M, Fung TT, Hu FB, et al. (2016). Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Internal Medicine, 176(10):1453-1463. PubMed
Zhong VW, Van Horn L, Greenland P, et al. (2020). Associations of Processed Meat, Unprocessed Red Meat, Poultry, or Fish Intake With Incident Cardiovascular Disease and All-Cause Mortality. JAMA Internal Medicine, 180(4):503-512. PubMed
U.S. Department of Agriculture, Agricultural Research Service (2019). FoodData Central, SR Legacy (food IDs 172420, 172421, 173757, 168917, 172475, 174272, 171477, 175168, 173424, 174033, 171312). FoodData Central