Researchers Point to the Optimal Protein Dose, Timing & Distribution to Maximize Muscle
We know protein is important for muscle repair, recovery and growth. And plenty of research has shown that many individuals would benefit from increasing their daily protein intake. Especially if they have body composition goals or are competitive athletes.
But it seems that it’s not just the daily amount that matters. Rather, protein intake should be looked at on a per-meal basis. Some of the world’s leading research labs looking at protein metabolism have shown that:
- There is a threshold of protein that needs to be hit in a given meal in order to maximize the anabolic response (muscle protein synthesis).
- An even distribution of protein across the day in 3–4 evenly spaced meals leads to more muscle protein synthesis than a “skewed” pattern of eating, where protein is very low in some meals and extremely high in 1 or 2 (as is typical in the general population).
To dive more into the details, I interviewed a number of these prestigious researchers in-depth on my evidence-based nutrition podcast Sigma Nutrition Radio.
Here are some comments from some of those researchers that might help piece this story together:
What Actually Is a “High-Protein” Diet?
Dr. Donald Layman (University of Illinois):
Yeah, I think that is actually a great question, and exactly, your point is
there’s a lot of confusion about it. If you look out into the literature, a lot
of people consider high as anything above the minimum RDA; anything
that’s above is high. If you look at the papers in the literature, there’s sort
of a general philosophy that the average diet’s around 15, so twice that, so
30% of the calories coming from protein.
So I frankly think that it’s the wrong way to define a protein diet. I think
we need to think in terms more of absolute amounts. And so the
requirement right now is at 0.8 grams per kg, most of the research is
pointing that the healthy adult probably needs somewhere between 1 and
1.5, so I would define high as something above those recommendations.
So for me, high becomes something above 1.7, 1.8 grams per kg, and so
we’re talking intakes of above 150 grams or more start getting into high
protein as far as I’m concerned.
What is Muscle Protein Balance?
Dr. Caoileann Murphy (University College Dublin):
So the muscle is constantly being turned over, meaning that the protein in the muscle is constantly being built up and broken down. So if you get up in the morning and consume a meal that contains protein, there’ll be a rise in amino acids in your bloodstream and that will stimulate muscle protein synthesis.
And at the same time, the insulin response to that meal will mildly suppress muscle protein breakdown, so as a result the rate of synthesis will exceed that of breakdown and that muscle protein balance will be positive. If you then go for a period of time without food, so let’s say in between breakfast and lunch, then the rate of breakdown will begin to exceed the rate of synthesis, so you would have a time of net negative muscle protein balance. And then that balance will swing into a positive situation again following lunch, for example, and then a negative and so on throughout the day.
So those fluctuations in net balance are roughly “equivalent.” So the time you spend in net negative balance tends to be roughly equivalent to the time you spend in net positive balance if you are a weight-stable younger adult who’s maybe not doing resistance training.
And then, over days, the net balance adds up over time to influence your muscle mass, so if you spend more time in a state of net negative muscle protein balance, then that would translate over time to the loss of muscle mass, whereas if you spend more time in positive net muscle protein balance, then that would result in muscle hypertrophy over time.
How Does Protein Initiate MPS?
Dr. Caoileann Murphy
So it’s the essential amino acids in protein that are responsible for the increase in muscle protein synthesis in response to protein intake or food intake. In particular, the amino acid leucine appears to have an important role as a trigger. It appears to be the most important amino acid; however, all of the essential amino acids are required to serve as building blocks for the building of new muscle protein.
How Important is Peri-Workout Protein Ingestion?
Dr. Jose Antonio (Nova Southeastern University, Florida)
So there’s a lot of people talking about the idea that when you consume protein somewhere around the exercise window (and specifically the post exercise window) that seems to be a lot of the benefit here. For instance, there’s a body of evidence that if you consume something that has protein pre- and/or post- exercise, it seems to elevate protein synthesis.
Now the argument against that is folks have said that if you’re eating enough protein in general throughout the day, does timing matter?
And it’s a good question. So let’s try to encapsulate who protein timing is important for who and who it’s not important for: If you’re someone who just exercises regularly three times a week, you’re not particularly into bodybuilding or high performance endurance sport events then it doesn’t matter. I mean if you’re just going to the gym 3 times a week, lift a few weights, it doesn’t matter if you do a precise nutrient timing strategy, because you don’t exercise hard enough. That’s sort of a fact of the matter.
However, if you’re a bodybuilder and your goal is to put on mass, it makes perfect sense consume something pre-, during and/or post- workout. Basically include protein as part of your meals that you consume throughout the day. If you’re an endurance athlete and you’re training for 2 hours… after riding a bike for 2 hours and running for 90 minutes, you need to get food in your body. Regular food or in the form of protein shake, you need to get it into your body. Waiting an hour is cool. Waiting 4 hours would be silly.
I think what people need to ask is this: is there any advantage in doing nothing post-workout? So the advantage is no. Not eating is never an advantage at all.
I see on social media tell you about nutrient timing is a waste of time, blah, blah, blah and they really have it completely backward. How about you know, Gatorade or a sports drink during exercise; will it help an athlete perform?That’s an example of nutrient timing that people seem to forget, where the timing, whether it’s a food, beverage or supplement, does critically matter. So the notion that nutrient timing is a dead strategy is baloney, it makes absolutely no sense.
It depends on the population or the type of athlete you are. Depends on your goals. Certainly it can help but can it ever hurt? No!
To me, from purely pragmatic thinking, it makes perfect sense that you consume in protein containing shake or food pre/post workout.
Why is it better to have an even distribution of protein across the day rather than a “skewed” pattern?
Dr. Caoileann Murphy
So the kind of rationale for a balance or an even pattern of protein intake throughout the day comes from the dose response relationship between the amount of protein consumed in the meal and the subsequent muscle protein synthetic response. So we know that in young adults, both at resting and post exercise, about 20 grams of protein appears to be sufficient to maximally stimulate muscle protein synthesis. That dose has actually been refined to about 0.24 grams per kilogram body mass per meal.
So if someone consumes less than that quantity of protein in a meal the muscle protein synthetic response is going to be sub-maximal, whereas if they consume over that quantity of protein the muscle protein synthetic response isn’t going to be any greater and those amino acids will just be oxidized. And we know that the muscle protein synthetic response is transient, so if you haven’t done exercise and you just consume a protein-containing meal, the rate of muscle protein synthesis will increase and be back down to baseline in about three hours.
So then if you were to consume let’s say about 0.24 grams of protein per kilogram body mass at each meal of the day, then the idea is that you would maximize your rate of muscle protein synthesis on each of those occasions. Whereas if you consume that typical skewed protein intake when you consume just a small amount of protein at breakfast, let’s say you have 12 grams in your bowl of porridge or whatever, then you’re going to have a suboptimal muscle protein synthetic response at breakfast. If you consume another suboptimal dose at lunch, let’s say 15 grams, then you’ll again have a suboptimal muscle protein synthetic response. And then at dinnertime, let’s say you consume 50 grams of protein. If you’re a young adult, then you’re only going to use about half of that to stimulate muscle protein synthesis and the rest will be, at least from the standpoint of muscle protein synthesis, wasted.
So over the course of the day then, your cumulative rate of muscle protein synthesis would be less compared to if you had a more balanced even pattern of protein intake with an optimal serving of protein for stimulating muscle protein synthesis at each meal.
Will MPS Always Drop Even We Stay Consuming Protein in-between Meals?
Prof. Kevin Tipton (University of Stirling)
The first evidence of this was from around 2000 I think when Mike Rennie was working in Bob Wolfe’s lab in Galveston. In one of the studies, they infused amino acids [into the bloodsteam] and got it to a hyperaminoacidemic level so that then protein synthesis was stimulated. But then they kept the infusion going for several hours. And what you often hear is people saying that’s what bodybuilders should do; they want to get constant protein meals to keep their amino acid levels in their blood high.
Well, what Mike showed in this study, and I should give credit to Julian Bohè who was the first author on that study, was that after a while the protein synthesis goes down despite the fact that the amino acid levels stay up in the blood.
So from that standpoint, it argues for having a meal, waiting a bit, having another meal, and not having too much in any given meal and spreading those out. So that’s the distribution that you were talking about. As of now, that seems to be the consensus recommendation.
So if we take identical twins and they eat the same amount, let’s say 120 grams [of protein] in a day, but one of them eats four doses of 30g and the other one eats 10g, 30g, 70g, and 10g, then the argument would be that the first twin would have a better anabolic response for the day. And if he carried that out over a long period of time that the muscle gains would be better. That’s the theory.
Why Does MPS Drop After 2–3 Even If Leucine Levels Are Kept High?
Prof. Donald Layman:
It was work by Gabe Wilson and Layne Norton, who were in my lab at the time, and we were trying to look at why, as you said, why is the duration of protein synthesis kind of a set amount? And that seems to be true in humans and animals alike. Once you trigger it, it will run about two hours, two-and-a-half hours, and then it goes back to baseline, and as you pointed out, leucine is still up. Again, I mentioned earlier, protein synthesis has two major parts. One is the initiation part, which is kind of like assembling the machinery, and then the elongation part where the protein synthesis has to run, and that process is extremely
energy-dependent and eventually the system just seems to run out of
So the important thing there is that we’ve got these two parts. One is the
initiation part, which is really assembling the machinery, and that’s where
leucine comes in; we sort of trigger it. But once the triggering has happened and leucine, whether it’s up or down, doesn’t really make much difference, it just has to be present as an amino acid then. And so then it really comes into what keeps elongation running, and from our research with Gabe Wilson again, it looks like it’s ATP. And so as the cell begins to run out of ATP, it triggers another mechanism called AMP kinase, which shuts down the elongation phase and protects it. And we show that if you give energy in the form of branched-chain amino acids or glucose, you can actually get it to run longer. So it has these two phases and leucine, again, is the triggering step, but then other things come into play as to how long it runs.
“If you eat over X grams of protein it is wasted because you just oxidize those extra amino acids” — Is this statement true or false?
Prof. Donald Layman:
It’s actually one of my biggest pet peeves in the area. I heard the exact same statement out of one of the experimental biology meetings in San Diego just two weeks ago. And the starting point that people have to recognize is that in an adult, sort of by definition, we’re at steady state. We’re at balance. We’re not gaining or losing protein. So no matter what you eat protein per day is going to be oxidized. So whether you eat 70 grams or 170, you’re going to oxidize that same amount or you have to be gaining weight. And so the idea that oxidation is bad I think is totally misleading.
And to go back to the leucine story for another piece of evidence, you talked about the kinetics of the leucine story — well, the KM, the kinetics for activating mTOR, is exactly the same concentration for the kinetics for activating the branched-chain dehydrogenase which oxidizes leucine. And so what the muscle has is a mechanism where it triggers protein synthesis and then it immediately starts depleting that leucine out of the cell to get ready for the next meal. And so oxidation goes hand in hand with the anabolic response. And one of the things we know is that during exercise — most of it’s been done with endurance exercise — is we burn the equivalent of about 10 grams of protein per hour just doing exercise, just burning it, and the majority of that is coming from branched-chain amino
acids, which is one of the reasons I like to use a branched-chain amino acid replacement after exercise because we have specifically selectively burned branched-chain amino acids during the exercise.
What Protein Sources Are Best For Hitting the Leucine Threshold?
Prof. Donald Layman:
One of the examples that we like to use is that, for example, quinoa is sort of everyone’s superfood right now and people talk about it having a complete amino acid mixture, but what people ignore is just how low in protein it is.
And so if you take something like beef, so everybody’s whipping boy is red meat, so if you take beef, beef has about 8.6% leucine, so to get 2.5 grams of leucine in beef you’d need about 29 grams of protein and that would require about 183 kcal (“calories”) to get to it.
If you did the same thing with quinoa; it only has about 6% leucine in it. So you need almost 42 grams of protein and quinoa is pretty diluted; you get almost 27 calories per gram of protein. So you need 1100 kcal of quinoa to just get to 2.5 grams of leucine. So for three meals a day just in quinoa, you’d have to eat 3,300 calories to get to the targets. So one of the things you have to remember with grains is they’re perfectly good, healthy carbohydrate foods but they’re lousy protein foods.
Dr. Caoileann Murphy:
So our available evidence is, based on the amount of protein that stimulates maximal muscle protein synthesis when the source of protein is high-quality and it’s not consumed along with any other macronutrients. So I think that there’s a real need for further work examining the dose response relationship
between protein and muscle protein synthesis when the protein is provided in context of normal foods and within mixed macronutrient meals because that’s how people typically consume their protein.
So the reason that that might be important is because if you consume a mixed meal, there is typically carbohydrate and fat and fiber, all of which would slow down the digestion and absorption kinetics, and it’s hypothesized that a rapid and pronounced peak in plasma essential amino acids and in particular leucine is important for stimulating muscle protein synthesis. So if you were to consume a mixed meal, it’s possible that the plasma amino acid response might be a bit more blunted, which could affect the muscle protein synthetic response. In addition, if we consider that if you were to consume a meal that contains, let’s say, 20 grams of protein, some of that protein will be coming from plant-based sources acids and lower in leucine, so we don’t necessarily know that that would have the same muscle protein synthetic response as a 20-gram bolus of high-quality whey protein, which is very rich in essential amino acids and rich in leucine.
Cliff Notes Summary (tl;dr)
- Muscle protein synthesis is an anabolic response that occurs in response to protein feeding and resistance training. On the protein front, it specifically relates to leucine intake. To maximize the MPS response, ~2.5g of leucine is required. This is known as the “leucine threshold”.
- To maximize the muscle protein synthesis response over the course of a day, it seems that 3–4 evenly spaced meals that surpass the leucine threshold is a prudent strategy.
- A meal containing 0.4 grams of protein per kilogram of bodyweight (g/kg BW) from a high-quality protein source will allow an individual to hit the leucine threshold. For most people this is somewhere between 20–40g.
- The best sources of protein for this purpose are animal proteins (particularly whey protein) due to their high branched-chain amino acid composition. Plant-based protein sources will mean a higher protein intake is needed to hit the required level of leucine.
- When MPS is “spiked” in response to a protein feeding, it will drop back to baseline within 2–3 hours. This drop will occur regardless of whether protein or amino acids continue to be fed and leucine remains high. This is potentially due to high demand of ATP required by cells for MPS (i.e. MPS is an energy-expensive process and the cell will stop MPS to conserve energy).
- MPS is only a proxy measure for muscle hypertrophy, not an exact correlate. Net muscle protein balance (MPS vs. muscle protein breakdown) matters more. And further, there are many other factors than influence actual hypertrophy outside of MPS and MPB.
- Of all the macronutrients, it seems that timing and distribution (versus simply total daily intake) is most important when it comes to protein. However, there are pragmatic examples of scenarios where we may not theoretically maximize MPS, yet still preserve and/or build plenty of muscle mass. For example, daily intermittent fasting.
Links to Full Audio Podcasts Referenced in this Article:
Episode 123: Donald Layman PhD, professor emeritus at the University of Illinois, discusses the "leucine threshold" and…sigmanutrition.com
Episode 118: Caoileann Murphy PhD is on the show to discuss protein metabolism, distribution and recommendations on per…sigmanutrition.com
Episode 116: Professor Kevin Tipton from the University of Stirling discusses nutritional interventions for injured…sigmanutrition.com