What’s the best protein for muscle gain? it might not matter

If you’ve ever wondered whether your post-workout protein shake needs to come from chicken or chickpeas, you’re not alone. There’s a lot of talk about which type of protein is best for building muscle – plant-based or animal-based.

And does it help to space out your protein intake throughout the day? Or get a bigger serving at dinner? A new study has tackled these questions head-on and the answers may surprise you.

Assumptions about muscle protein synthesis

Researchers at the University of Illinois Urbana-Champaign designed a nine-day clinical trial to test three common assumptions about muscle protein synthesis.

The experts wanted to know: Does the protein source – plant versus animal – impact muscle building? Does timing throughout the day affect how your body uses protein? And is there any real benefit to moderately high protein intake for muscle growth?

According to the study, the answer to all three questions is no.

Rethinking what builds muscle

“The longstanding belief or the current dogma was that animal-based protein sources were better, particularly for the muscle-building response,” said Nicholas Burd, one of the lead researchers.

This belief was based on previous studies showing that animal protein led to a stronger muscle-building response after a single meal. “And so, our general hypothesis, based on these previous studies, was that the animal-based eating pattern would be more effective at supporting the muscle-building response,” said Burd.

But there’s a catch. Many of those older studies were based on a single meal, not what happens over the course of a whole diet. The new study aimed to better reflect how people actually eat – whether they follow a plant-based or omnivorous diet over time.

Burd pointed out that a previous 10-week trial found similar muscle synthesis in vegans and omnivores, but those participants consumed high levels of protein (1.6 to 1.8 grams per kilogram of body weight per day), which goes beyond what most people need to gain muscle. That earlier study also relied heavily on plant protein supplements, which doesn’t mirror how real vegans eat.

Protein choices put to the test

To explore this further, the team recruited 40 healthy adults between age 20 and 40. For seven days, everyone ate a standardized diet to normalize their nutrition. Then they were randomly assigned to either a vegan or an omnivorous diet for the trial. All meals were provided by the researchers, with most eaten at home and some in the lab.

For the omnivorous group, about 70% of the protein came from animal sources like beef, chicken, pork, eggs, and dairy. The vegan diet used whole plant-based foods, carefully combined to provide complete proteins with all the essential amino acids.

Each dietary group was split again. Some participants had their protein intake spread evenly across three meals. Others ate five meals per day with the majority of their protein at the end of the day. Everyone did muscle-strengthening workouts every three days and wore accelerometers to track physical activity outside the lab.

To measure muscle protein synthesis, participants drank deuterium-labeled “heavy water.” This allowed researchers to trace the incorporation of amino acids into muscle tissue over time. Muscle biopsies were taken before and after the trial.

Post-workout protein is key

The results showed no difference in muscle protein synthesis between the vegan and omnivorous diets. Timing of protein intake didn’t matter either.

“It was thought that it was better to get a steady-state delivery of nutrients throughout the day,” Burd said. “I also thought that if you’re getting a lower-quality protein – in terms of its digestibility and amino acid content – that perhaps distribution would make a difference. And surprisingly, we showed it doesn’t matter.”

The findings build on earlier work from Burd’s lab that suggested consuming more than 1.1 grams of protein per kilogram per day doesn’t lead to greater muscle gains. That’s in line with what many Americans eat naturally.

Now, Burd has a simple answer when people ask him what to eat to build muscle: “It’s the kind you put in your mouth after exercise. As long as you’re getting sufficient high-quality protein from your food, then it really doesn’t make a difference.”

The full study was published in the journal Medicine & Science in Sports & Exercise.

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