Vegan vs. omnivore: New study finds no difference for building muscle

Research has found that vegan diets during weight training do not impact muscle building. It concluded that following plant- or animal-based diets made no difference in muscle protein synthesis.

“The longstanding belief or the current dogma was that animal-based protein sources were better, particularly for the muscle-building response,” comments Nicholas Burd, a professor of health and kinesiology at the University of Illinois Urbana-Champaign, US, who led the new study with graduate student Andrew Askow. 

He explains that the belief is rooted in science, as previous studies found that an animal-based meal provided more stimulus for muscle protein synthesis than a vegan meal. “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.”

However, measurements made following a single meal, according to Burd, may not accurately represent the long-term effects of eating a balanced vegan diet.

Burd says that the best type of diet for muscle building is 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.”

Omnivore and vegan diet test

The research was conducted on 40 healthy, physically active 20- to 40-year-old adults who underwent a seven-day “habituation diet” to standardize their nutritional status. After this, they were randomly assigned to either a vegan or an omnivorous diet. 

Study first author Andrew Askow co-led the research with Burd (Image credit: Andrews Askow).The researchers ensured the vegan diet balanced the amino acid content of the meals so that participants consumed complete proteins. Protein (~70%) in omnivorous meals came from beef, pork, chicken, dairy, and eggs.

The vegan diet balanced the amino acid content of the meals, ensuring that participants consumed complete proteins. The study suggests that the best type of muscle-building food is consumed after exercise, with sufficient high-quality protein from the food.

In the lab, participants exercised their muscles every three days. They drank “heavy” water labeled with deuterium, a stable isotope of hydrogen. This enabled the researchers to trace the amino acids’ incorporation into muscle tissue.

Burd says he saw no differences in rates of muscle protein synthesis between those eating vegan or omnivorous diets. There was also no effect on protein distribution across the day that impacted the rate of muscle building, unlike results from past studies of acute responses to dietary interventions and weight training.

“It was thought that it was better to get a steady-state delivery of nutrients throughout the day,” he says. “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.”

In recent research, two recent scientific reviews bolstered the case for HMB (β-hydroxy β-methylbutyrate) as a proven, science-backed nutrient that supports muscle mass, strength, and physical function in older adults. This nutrient is derived from the amino acid leucine, found in animal- and plant-based proteins.

A New Zealand study evaluating protein intake and quality revealed that three in four vegans ate sufficient protein. Still, half didn’t meet daily requirements for the essential amino acids lysine and leucine when accounting for protein digestibility.