Plant protein vs. animal protein — is one better for muscle growth? Dietitians explain

Do you need to eat muscle to gain muscle? The argument over plant vs. animal protein is nothing new, and it comes down to amino acids, the building blocks of protein. Your body can’t make nine of them on its own. These are called essential amino acids. Animal proteins contain all nine in the amounts the body needs, explains sports dietitian Lindsey Moser. Plant proteins, however, earned a reputation for being “incomplete” because they’re lower in one or two. But is the debate really that clear-cut? Not quite.

Leucine, a branched-chain amino acid, tends to drive the conversation. It activates muscle-building signaling pathways and is lower in many plant proteins. A 2018 analysis found that many protein isolates in plant-based powders and supplements had less leucine than whey, and the belief that whey is superior for building muscle gained momentum.

Since then, studies have challenged the idea that you need animal products to build muscle, though the source still matters. To dig into the details, I used my expertise as a registered dietitian to review the latest research and spoke with two fellow dietitians.

So, what does the research actually say?

When protein intake and training are matched, plant and animal protein can lead to similar muscle gains, especially when the plant sources include soy, which has an amino acid profile similar to milk’s. A 2025 review of 30 randomized trials found that animal protein had a small edge for building muscle mass overall. But soy and milk protein performed the same, and strength and physical performance were similar between plant and animal sources. The gap showed up with non-soy plant proteins, such as rice, chia, oat and potato, and with plant-based diets, though fewer trials tested those.

Smaller trials of people who lift weights show similar results. For example, in a 2021 study published in the journal Sports Medicine, young men — half habitual vegans and half habitual omnivores — gained significant muscle mass after increasing their protein intake to 1.6 grams per kilogram of body weight per day and strength training twice a week, with no notable differences between the groups.

A 2025 University of Illinois study points the same way. Forty healthy, active adults who followed either a vegan or an omnivore diet, along with a weightlifting regimen, showed no differences in the processes that build muscle between the groups. The study lasted only nine days, so it can’t settle the debate, and it was sponsored by the beef industry. Still, it adds to research suggesting that total protein and strength training matter a great deal for building muscle, though the source can affect how much protein you need.

When plant-based eaters do fall behind, Moser says the reason is often logistics, not effectiveness. “When total protein intake and leucine content are matched, plant-based eaters build and maintain muscle just fine. The catch is you usually need to eat a bit more volume of plant protein to hit the same targets, since it’s slightly less concentrated per gram than something like chicken or eggs.”

A 2024 review in the Journal of the International Society of Sports Nutrition backs that up. It estimates that vegan and vegetarian athletes may need roughly 20% to 40% more plant protein than animal protein to get similar amounts of essential amino acids and leucine, especially during resistance training.

Where the two differ

Both types of protein can support muscle gains, but each has benefits that the other doesn’t.

Advantages of animal proteins

• More protein in fewer bites: “Animal proteins tend to pack more protein into a smaller amount of food,” says registered dietitian Talia Follador. For example, 100 calories’ worth of roasted lean chicken provides around 20 grams of protein. To get the same amount in lentils, you’d need to eat more than a cup, which has about 260 calories. “It’s simply easier to hit a high protein target without excess calories or fiber load, which is useful for certain training goals or medical situations,” says Moser.

• Excellent source of B12: Some nutrients, such as vitamin B12, are found naturally only in animal foods. Vitamin B12 is needed for red blood cell and nerve tissue production, so people who eat few or no animal products often need fortified foods, such as nutritional yeast or some plant milks, or a B12 supplement.

• Better bioavailability of iron and zinc: Some plant proteins contain iron and zinc, but compounds called phytates bind to these minerals and reduce how much the body absorbs. Animal proteins don’t contain phytates, so these minerals are generally easier to absorb.

Advantages of plant proteins

• Good or excellent source of fiber: Animal proteins may pack more protein gram for gram, but plant-based sources like beans, lentils, nuts, seeds and soy also provide fiber, a nutrient more than 90% of Americans don’t get enough of, according to the American Society for Nutrition. “Fiber supports digestive health, can help manage cholesterol and blood sugar and feeds beneficial bacteria in the gut,” says Follador. A 2025 Icelandic study found that 74% of vegans met fiber goals of 25 grams a day for women and 35 grams a day for men (similar to U.S. recommendations), while only 8% of omnivores did.

• More heart health benefits: “Many plant protein sources are relatively low in saturated fat and provide unsaturated fats, fiber and other nutrients associated with cardiovascular health,” says Follador. Some animal proteins, particularly red and processed meats and full-fat dairy, tend to be higher in saturated fat. A 2024 observational study of nearly 203,000 people found that those with the highest ratio of plant to animal protein had a 19% lower risk of cardiovascular disease and a 27% lower risk of coronary heart disease over 30 years, though it shows an association, not cause and effect.

• Beneficial plant compounds: Beyond macronutrients and micronutrients, plants contain a wide variety of bioactive compounds you won’t find in animal products. “Plant proteins can provide antioxidants and other phytochemicals that may help protect cells from oxidative stress and support long-term health,” says Follador.

Plant protein vs. animal protein: Which one wins?

If your primary goal is to build or maintain muscle mass, what matters most is eating enough protein. If you’re plant-based, that may mean eating more than an omnivore would to get the same amount of amino acids, particularly leucine.

Plant protein can be more budget-friendly and provide beneficial nutrients, such as fiber, along with antioxidants, but it often takes more time and energy to plan and prepare. Animal protein can be pricier, but it requires less volume to hit protein goals.

“Athletes, older adults and people with higher protein needs can meet their needs with either plant or animal protein,” says Follador, adding, “Someone eating primarily plant-based may just need to be a little more intentional about portions, total protein intake and variety.” If you’re shopping for a vegan protein powder, look for one made from soy or pea, or a blend that includes one of them.

Of course, there are many other reasons you may choose one over the other. Allergies, intolerances, religious reasons, personal preferences, ethical or environmental concerns, medical needs and health priorities can all tip the scales depending on the situation. Where you live and which foods are more readily accessible can also play a role.

With all of that in mind, here’s a quick overview of the pros and cons of each:

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