Exercise researcher Nicholas Burd said his field has long believed that earning profits in a gym requires eating meat or other animal products.
This is not a question of brother science – the idea is supported by well-controlled research.
In the laboratory, whey protein, such as whey, is better synthesised muscle protein than eating soy or other plant protein sources.
"In my opinion, animals (protein) are better than plants," said Burd, director of nutrition and exercise at Urbana-Champaign, University of Illinois.
Meat is rich in essential amino acids and we need to make muscles and reflect the composition of our own skeletal muscle.
Plant-based foods also have some concentrations that are essential to all essential amino acids, i.e. muscle base, but are important for protein synthesis.
But in recent years, more control studies have been conducted, overturning previous hypotheses - suggesting that plant proteins can be compared with muscle.
“In grams of form, animal protein is certainly higher than plant-based protein,” said James McKendry, a nutritional and aging at the University of British Columbia. “But if you are consuming enough (plant-based protein), and in the context of a regular meal, these differences really don’t appear in the wash.”
Some of the latest data comes from a trial by Burd, recently published in the Journal Physical and Exercise Medicine and Science. It recruited 40 young people and randomly assigned them to vegetarian or omnivorous diets.
Participants had three weightlifting sessions over nine days and the researchers provided them with all meals. At the end of the study, they activated the participants’ muscles, which allowed them to calculate protein synthesis, Burd said.
They found that both diets have the same "muscle building potential", and their data suggest that long-term muscle growth will be the same.
The experiment also examined whether time is important. Some people back up their protein at the end of the day, as many tend to eat supper, while others take their protein intake.
There is no difference here.
"I think this is an important study, in terms of our attitudes about where to get protein from," said Benjamin Wall, a researcher at the University of Exeter.
The new data echoes Wall found in his own trial a few years ago, which compares muscle-building animal and plant proteins.
He said historically, one of the main reasons for the inferiority of plant protein is the study of the effects of single meals within a few hours.
“We have several studies now showing that there are much less differences,” he said.
In Wall's trial, participants' high-protein diet was about 2 grams per kilogram of body weight. By comparison, the new Illinois University study reduced it to 1.2 grams, reflecting how much protein Americans tend to consume every day and are still 50% higher than the U.S. recommendation.
New research has warnings.
You can only infer too much from short-term research that can't measure muscle growth or strength changes, including only young people.
But based on what he and others have discovered, Wall believes that the discoveries will be realized in a longer time.
Research like Burd's is more accurate to provide participants with a balanced meal because they do not rely on self-report. On the other hand, they don’t have to “treat the real world challenge that consuming a high-protein diet can be harder.”
Some plant-based foods have relatively high proteins, such as beans (a cup of cooked lentils) and tofu (22 grams per ½ cup). There are also some cereals such as quinoa (8 grams of cooked cup per cup), such as broccoli (2.6 grams per cup) and vegetables.
But meat is protein-intensive, so you can end up eating the same calories as the same protein than the plant. Also, you must be careful to eat a variety of plant-based foods to cover all the essential amino acids the body needs to maximize muscle growth.
“Many people in the world know it,” McKendry said. “If rice is combined with beans, they will have complementary amino acid profiles.”
For example, peas are a good source of the amino acid leucine, which is essential to turn on protein synthesis, but they are low in methionine, which means you need to look for it elsewhere, such as rice or soy.
“As long as they are balanced and you eat enough protein, a vegetarian diet is just as good as that,” Bird said.
How much protein you need is another (sometimes splitting) issue.
For those trying to build muscle, Wall says 1.6 grams of protein per kilogram of body weight is a "widely accepted number to optimize training adaptation," although that depends heavily on your activity level, goal, age and other factors. (In pounds, the protein per pound of body weight is about 0.72 grams of protein.)
"Apart from that, the rate of return is lower," McKendry said.
But it is important to remember that “protein is really the icing on the cake”, which is in the muscle building equation. The larger piece is resistance training itself, and studies have shown that this training is good for longevity, brain function and cardiovascular health, to name just a few.
"It doesn't matter how much you consume - if you don't resist training step by step, you won't build too much muscle," he said.