A new study has shown that when it comes to building muscle, it doesn’t matter whether your protein comes from plants or animals.
Researchers at the University of Illinois Urbana-Champaign wanted to answer three questions:
Does the source of protein affect muscle growth? Does it matter how you spread out your protein during the day? And do moderate levels of protein work just as well? The answer to all three was no.
For a long time, many people believed that animal-based proteins, like meat and dairy, were better for building muscle. This belief came from earlier studies that looked at what happens in the body right after eating a single meal.
These studies found that animal proteins caused more muscle growth than plant proteins. But those were short-term studies. This new research looked at what happens over a longer period of time when people follow real diets and work out regularly.
In earlier trials, people eating vegan or meat-based diets and doing strength training had similar muscle growth.
But those studies used very high protein amounts—more than most people eat in real life—and gave vegans most of their protein through supplements, which doesn’t reflect a typical vegan diet. So, the new study focused on real food and more normal eating habits.
The researchers worked with 40 healthy adults between the ages of 20 and 40. All of them followed a special diet for a week to make sure they started the trial in the same condition. Then they were split into groups eating either vegan or omnivorous (meat-containing) diets.
The vegan meals used a variety of plant foods to make sure participants got all the essential amino acids—the building blocks of protein. The meat-based meals used common animal protein sources like beef, chicken, eggs, and dairy.
The two main groups were also divided again based on how they ate their protein. Some people ate the same amount of protein at breakfast, lunch, and dinner, while others ate different amounts across five meals, with more protein later in the day.
All participants did strength training every three days and wore activity trackers when not in the lab. Each day, they also drank a special type of “heavy” water that allowed researchers to track how their muscles used protein. Muscle biopsies were taken at the start and end of the study to measure changes.
The results were surprising. No matter what kind of protein the participants ate, their muscles grew at the same rate. It also didn’t matter how the protein was spread throughout the day. As long as people ate enough high-quality protein and exercised, they built muscle.
Lead researcher Professor Nicholas Burd said he expected animal proteins to work better, and he also thought that spreading protein out evenly might help more with muscle growth. But the study proved otherwise.
“Now if someone asks me what food is best for muscle building, I’d say: it’s the one you eat after your workout,” he said. “If you’re getting enough good-quality protein, it doesn’t matter where it comes from.”
This research was supported by the Beef Checkoff program, managed by the National Cattlemen’s Beef Board.
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