Can the body only absorb 20 g protein per meal?

Categories: Videos & podcasts


00:00 Introduction

00:28 Digestion, absorption, metabolism

01:40 Muscle Protein Synthesis & Muscle Full Effect

03:42 3 important caveats

07:40 The Meal Frequency project study

08:38 Summary


Is it true that the body can only absorb 20 grams of protein per meal? And if so, what are the implications of this for your daily meal frequency, or how many meals you should eat for maximum muscle growth? This is a topic that is riddled with truth, myths and accordingly a lot of confusion. So in this video, I hope to clear up that confusion and present you a clear idea of what your body does with protein and what that means for how many meals per day you should eat.

To start with, none of this has anything to do with digestion or absorption. If we take the idea at face value that the body can only absorb 20 grams of protein per meal, it is decidedly false. It is very clear that the body can easily absorb more than 20 grams of protein per meal. What people mean is they’re talking about protein synthesis. So let’s get our terms straight here. When protein goes into your body, it first has to be digested. Digestion basically means it’s broken down into pieces that the body can absorb into the body. So absorption requires the nutrients that you consume going into the body and generally being available in the bloodstream. After absorption, the body can metabolize these nutrients. So you want your body to not just digest and absorb the nutrients, but also metabolize the protein. And that means that the body can use it for, for example, muscle protein synthesis in your muscles, which makes them bigger and therefore makes you more muscular and stronger.

So it’s definitely not the case that there’s any limit on digestibility or absorbability of protein. You would have to consume absolutely ludicrous amounts before that will ever become an issue. The body’s energy harvest is exceedingly efficient and the body has no problems getting all the protein as well as all the calories from the food that you eat.

So absorption is really not an issue. What is an issue is muscle protein synthesis. And here there is a lot of truth behind this idea that after 20 grams of protein, at least high quality protein, such as whey protein or dairy protein in general. There is very little additive effect anymore of going higher up in protein. As you can see in the graph here, after a 20 grams of protein per meal, there is essentially no further stimulation of muscle protein synthesis, especially not at rest. Why is this? It’s because of what researchers call the muscle full effect, as you can see in the graph here. If you just keep pumping in amino acids into the blood, then at some point your body is not going to respond to that anymore. The body will be refractory to it. And the mechanism there is essentially that you cannot eat your way to Mr. Olympia. So the body will only stimulate a certain amount of muscle protein synthesis that it needs because muscle protein synthesis is a very energy intensive process. The body doesn’t just want to go around to building a lot of muscle just because one time you killed a deer and you ate always protein and subsequently the body makes you Ronnie Coleman always protein and subsequently the body makes you Ronnie Coleman It doesn’t work that way. In nature, of course, the body has evolutionarily adapted to only building muscle when it’s absolutely necessary, because otherwise it would waste a lot of calories and energy on that If you don’t need the muscle mass, that is not adaptive. So the body will only build muscle to the extent that you stimulate that muscle growth, usually with strength training.

So you could say that in terms of muscle growth being a glass and how about you fill up that glass Strength training basically determines the size of the glass and nutrition determines how much of that glass you are filling. In other words, researchers will say that nutrition is permissive for muscle growth, where as strength training is the thing that really stimulates the muscle growth. This is a little bit of an oversimplification, but I think it drives the point home well for most people. So it is true that for in most situations, after 20 grams of high quality protein, there is no additional further effect on muscle protein synthesis.

However, there are a few very important caveats. First, this refers mostly to research at rest or research in post exercise period where people trained with relatively low training volumes or only exercised a single body part. When we look at research in which people do a substantial training volume, especially of full body training, we see that the muscle full effect increases.

So the ceiling of muscle growth increases up to about 40 grams of high quality protein. That’s a pretty big difference of course, it’s about double. That means that after your workouts, you can utilize significantly more protein. Nevertheless, 40 grams of protein or about 0.6 grams per kilogram body weight is still not that much. And it’s mostly the first meal after the workout in which this occurs. However, there is another potentiometer of muscle protein synthesis and anabolic signaling, and that’s fasting. After longer periods of fasting, we see that anabolic signaling can reach higher levels than before. This makes sense in terms of the body having a greater demand This makes sense in terms of the body having a greater demand for muscle protein synthesis when it didn’t have a lot of muscle protein synthesis in a period before. Whereas if you keep flooding it with amino acids, then you’ll see that the body has the muscle full effect and it becomes refractory to further stimulation with amino acids. So again, makes perfect sense from an evolutionary point of view if you are starving in the period before and you get access to a lot of protein, then a body will use that protein to repair all the muscle and lean body mass that was lost. A higher level of protein that the body will use to restore and build new lean body mass and therefore stimulate muscle protein synthesis. Caveat three is that this only refers to muscle protein synthesis.

We also care about muscle protein breakdown. And there are a few studies that find that while you don’t stimulate more muscle protein synthesis beyond 20 or 40 grams or 20 or 40 grams of protein, depending on whether you were at rest or after a serious training session, we see that muscle protein breakdown levels do increase past that point. Now, muscle protein break down levels, they don’t change as much as muscle protein synthesis levels, muscle protein synthesis levels are the principal driver of changes in muscle mass and total protein turnover and net balance levels. Why? Because it’s much more efficient for the body to stop synthesizing new proteins than to change muscle protein break down levels. Basically, the body doesn’t go about breaking down protein for no reason. Muscle protein breakdown is usually there because either it’s really necessary Muscle protein breakdown is usually there because either it’s really necessary to catabolize muscle tissue, or it’s part of muscle repair.

You can think of this as like building a house, building muscle. It’s like building a house when you want to add a balcony, for example, to your house, you can’t just tack the balcony onto the house as is right. You need to open the wall, create the door, maybe add some windows, maybe even break out the whole part if you want a nice open view, yada, yada. So it’s just like that with muscle growth. You can’t just add a piece of muscle on top of it. You first need to remodel the tissue and that involves some protein breakdown. So usually muscle protein breakdown levels, they don’t actually have that much. So, long story short muscle protein break down levels, they’re not nearly as high as synthesis levels and they don’t change as much. So the practical utility of this isn’t major, but there is research indicating that there will be a net further increase in muscle growth potential even beyond 20 to 40 grams of protein per meal because of a further reduction in muscle protein breakdown, even when muscle protein synthesis is already pretty much maximized.

Now, I would say that the research methods used to estimate the level of protein breakdown in these studies is a bit controversial. There have been questioned. So yeah, with that in mind, take it with a little bit of a grain of salt. But I think it does explain why the 20 gram absorption limit doesn’t really pan out in practice because if you think about it, that would require at least six meals per day to maximize muscle growth. So theory aside, what do the actual data say? Well, we have a few studies on training frequency, and generally the trend is that we don’t see these clear effects that you would expect based on the ceiling of muscle protein synthesis for muscle growth, for long term muscle growrth in studies.

For example, one of the best and most interesting studies I think on this that we have is the Norwegian Meal Frequency Project, where they had a group of trained lifters do a training program with either three or six meals per day, all else generally equal. I would say that there was a little bit of problem with the calorie control, which we’ll get to in a moment. But overall, they found that the three meal group had better gains than the six meal group. They were roughly equal with a trend towards better gains in three meals. That was probably because the three meal group had a slightly higher energy intake. But if we compare the research on protein intake to that of energy intake, we see that the effects of energy intake on muscle growth are very small, whereas the effects on protein intake are much clearer. So overall, I would say that this is pretty strong evidence that there are probably not massive benefits to consuming more than three meals per day, especially if you time your protein well, where you have most of your protein in the post-workout periods when the muscle full effect is delayed and you can have higher levels of muscle protein synthesis.

So I think that basically sums up the whole practical application of this video. You need at least three meals a day, most likely because of the strong limit to how much muscle protein synthesis your body will allow you to stimulate in a single meal. However, because that limit increases with fasting after exercise and might increase to a higher level for muscle protein break down than for muscle protein synthesis, I think it’s probably not necessary to have more than three meals per day. The current data don’t show any advantage of that. If you like this type of evidence based content, I’d be honored if you like and subscribe.

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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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