Is there a limit to how much protein your body can use from one meal? The answer may surprise you.
Protein is a vital nutrient. It makes up our muscles, organs and skin cells. Our bodies can make some amino acids, which are the building blocks of protein, but there are nine “essential” amino acids that we can only get from food. And since our bodies don’t store protein, we have to eat a minimum amount of it every day to prevent health problems like muscle loss, thinning hair and a weakened immune system.
But you may have heard the claim that your body can “use” only about 20 to 30 grams of protein from a meal to build and maintain muscle. That’s roughly the amount in a three-ounce cooked chicken breast. If you eat more than that at a time, the saying goes, then the remainder will be excreted from your body or perhaps burned for energy. According to nutrition and exercise experts, this claim has been conventional wisdom for decades.
“This has been around for God knows how long,” said Brad Schoenfeld, a professor in the program of exercise science at Lehman College in New York and a muscle-building researcher. “It’s all over the internet.”
Scientists have looked into how much protein our bodies can use at one time to build and maintain muscle. The reality is that if there is an upper limit, then it hasn’t been discovered yet. But it’s certainly far more than 30 grams of protein. At least one study found that even when people consumed 100 grams of protein in one sitting, their bodies still metabolized and used it all.
This is how much protein you need
The National Academy of Medicine says that the amount of protein most adults need on a daily basis is 0.8 grams per kilogram of body weight, or the equivalent of 0.36 grams per pound of body weight. That’s about 54 grams of daily protein for the average sedentary adult, which you can get by eating four ounces of grilled salmon, a three-ounce grilled chicken breast and one hard-boiled egg.
But if you exercise regularly, then you need to eat more protein. That’s especially the case if you lift weights. Resistance exercise causes mechanical stress that breaks down muscle fibers. This leads to an increase in the repair and growth of muscle tissue, also known as muscle protein synthesis.
This process can be stunted if you don’t eat enough protein, because your body won’t have the amino acids, or building blocks, that it needs to create new muscle tissue. So, according to some experts, you should aim for at least 25 grams of protein per meal from both animal and plant sources.
Is there a limit to how much protein you can absorb?
But some experts have also suggested that there is a limit to how much protein your muscles can utilize for muscle protein synthesis — and that once you hit this limit, any additional protein can’t be used to build muscle. This is known as the “muscle full” concept.
Some research has suggested that less is more. In one study, for example, researchers recruited two dozen healthy men, split them into three groups, and had them do a session of strength training that consisted of leg extension exercises. Then they gave them 80 grams of whey protein, which was administered in different ways over a 12-hour period. One group consumed 20 grams of whey protein every three hours. Another group was given 40 grams of whey protein every six hours. And the third group consumed 10 grams of whey protein every one-and-a-half hours after they exercised.
The researchers also performed muscle biopsies on the participants. They found that consuming 20 grams of whey protein at a time caused the greatest increase in muscle protein synthesis throughout the day, suggesting that there was no benefit to consuming larger amounts.
But other studies have suggested that under the right circumstances, your body can utilize larger amounts of protein.
In one study, researchers recruited a group of healthy young men and had them do two separate, whole-body resistance training sessions that were two weeks apart. After one exercise session, the men consumed 20 grams of whey protein. After the other training session, they consumed 40 grams of whey protein.
The study found that muscle protein synthesis was higher when the people consumed 40 grams of whey protein. But why? The researchers speculated that by training their entire bodies — rather than exercising only their legs or other isolated body parts — the participants activated a lot more muscle mass, causing their bodies to need a lot more protein.
In another study, scientists compared what happened when men and women ate two different meals on different occasions. One meal contained about 40 grams of protein from beef patties, and the other meal contained roughly 70 grams of protein from beef patties. The researchers found that the 70-gram-protein meal elicited a greater muscle-building response from the participants, mostly because it inhibited the breakdown of muscle.
And the most recent and perhaps most striking study of all looked at what happened when young healthy men did a full-body resistance training session and then consumed one of three beverages. One drink contained 25 grams of milk protein, another drink had 100 grams of milk protein, and the third — a placebo — contained no protein at all.
The researchers found that the larger amount of protein led to higher rates of muscle protein synthesis and protein absorption, suggesting, as they put it, “that the anabolic response to protein ingestion has no upper limit.”
Your personal protein preference
For most people, eating 100 grams of protein in one sitting would be almost unthinkable, said Jose Antonio, a professor of health and human performance at Nova Southeastern University in Florida and co-author of a recent report on protein misconceptions. That’s the amount of protein in four McDonald’s Big Mac sandwiches, or roughly three-and-a-half Chick-fil-A grilled chicken sandwiches.
“I don’t recommend that people eat 100 grams of protein at one meal,” he said. “Do you know how hard that would be?”
Still, he said, the data suggest that if you did manage to eat that much protein, then your body could still utilize it under the right circumstances. “We don’t know the upper limit,” he added. “But it’s not 100 grams.”
That being said, more research is needed, especially on how protein absorption can vary between men and women. Most of the studies conducted on protein and muscle building have been on men.
Schoenfeld said that how much protein your body can use depends on the amount and type of exercise you do, the type of protein you consume (some types of protein are more slowly absorbed than others), whether you’re eating a meal with a lot of fat and carbs and many other factors.
But he pointed out that muscle protein synthesis starts to diminish as people eat more and more protein. “It’s not a linear response where you get twice as much muscle protein synthesis from 80 grams as you get from 40 grams,” he said. “The curve does level off. The dose response becomes less and less as you’re eating more and more protein, from a muscle-building stance.”
He said that the most important thing to focus on when it comes to protein is just making sure that you get a sufficient amount of it over the course of your day.
For many people, there are benefits to spreading your protein out among several meals. It can help regulate your blood sugar and promote satiety. But if you prefer to compress your daily protein intake into just one meal per day, for example, that doesn’t mean that most of the protein that you eat is going to go to waste, he said.
“It comes down to personal preference,” he added. “If you prefer to spread your protein intake across three or four meals, then do that. But not everyone can do that. And stressing about it, at least from the evidence that we have, is not warranted.”
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