Protein Requirements for Muscle Growth

The Protein BookWhile I’m working on a few other articles on other topics (including training to failure, the metabolite theory of growth and a detailed examination of what muscular tension is and isn’t), I want to do a quick update on the topic of protein requirements for athletes.  This is a topic with literally decades of history behind it.

Early on, the debate was primarily between scientists, who often argue that activity did not increase protein requirements and athletes who did (the athletes, to a first approximation turned out to be correct, by the way).   There have also been long standing debates between scientists on different sides of the same debate (some of the big names that will come up in this piece are Stuart Phillips, Kevin Tipton and Robert Wolfe) with some giving relatively lower recommendations (but still higher than the RDA/DRI levels) and others relatively higher.

And today I want to look at that.  More specifically, I want to look at a commonly made claim/statement that has been percolating through the online fitness space that, while it sounds logical, turns out to be unbearably incorrect.  Said recommendation also happens to primarily come from one of the researchers who has been on the relatively lower end of protein requirement recommendations for a couple of decades now which shouldn’t be much of a surprise.  But others are repeating his recommendations without giving it much (apparent) thought.

Now, this is a topic I’ve written about before and, if we go back 11 years, I published an entire book on Protein Requirements for Athletes in 2008 (which also contained a fairly detailed discussion of the topic of protein requirements for athletes).   And putting it out up front, I tend to be on the higher relative intake levels for protein which I feel is correct based on the extant research.  I’ll present it and you can make up your own mind.

Note: I am ONLY talking about protein requirements under non-dieting conditions.  It’s well established that protein requirements go up with dieting and can be especially high for lean athletes (though one individual in the field who pretends to be research based has dismissed this review paper OUT OF HAND because it contradicts his dogma).

Note 2: This article is also only about men.  That’s where most of the research has been done and differences in women’s physiology, etc. alter their requirements downwards by about 15-25% or so for various reasons.  This is all discussed in detail in The Women’s Book Volume 1.  Mind you, the exact same comments I will make in this article still hold for women, only the numbers vary.

Note 3: This information also does NOT apply to older folks.  There is an anabolic resistance that occurs with aging and it’s pretty well established that their protein requirements are systematically higher than younger individuals (they also respond differently to fast acting proteins and protein pulsing so it’s a different system).

Basically, I’m focusing on the protein recommendations for young training males seeking to increase muscle mass here only.

Onward and upward.

The Claim About Protein Requirements for Athletes

First let’s look at the statement that has been made and that is being endlessly repeated throughout the fitness space which is this.

Consume ~0.4 g/kg body mass (i.e., 0.24 plus 0.06 with protein added to account for the influence of other macronutrients in meals and protein quality), to maximally stimulate MPS following a period of rest or exhaustive resistance exercise.

To maximize muscle protein accretion with resistance exercise, daily protein intakes should be ~1.6 g/kg/day and up to 2.2 g/kg/day. This intake can be achieved by ingesting 3 meals, each containing ~0.53 g/kg protein, or 4 meals containing ~0.4g/kg protein.

This comes from a paper titled Recent Perspectives Regarding the Role of Dietary Protein for the Promotion of Muscle Hypertrophy with Resistance Exercise Training published in 2018 in the journal Nutrients (Stu Phillips is the final author and has always skewed towards the low end of protein requirements) and I’ll address the origin of the claim in a second.

Basically it is saying that there is a threshold effect where more protein than the above value does not further increase skeletal muscle protein synthesis, hence it represents a per meal maximum above which no more is beneficial and therefore represents a value for optimal protein requirements if integrated across multiple meals per day.

This claim has been repeated elsewhere.  For example in a paper titled How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution published in the Journal of the International Society of Sports Nutrition (I’ll let you check the authors yourself so I don’t sound like too much of a broken record), it’s stated:

It is therefore a relatively simple and elegant solution to consume protein at a target intake of 0.4 g/kg/meal across a minimum of four meals in order to reach a minimum of 1.6 g/kg/day – if indeed the primary goal is to build muscle. Using the upper CI daily intake of 2.2 g/kg/day over the same four meals would necessitate a maximum of 0.55 g/kg/meal.

Which just reiterates what was written in the first paper (and goes back to that age-old idea that only 30 grams of protein or whatever can be used per meal, another utter piece of bs).  But from these (and probably other) sources, the claim has become commonly stated/repeated/regurgitated online.

Oh yeah, for everybody not from Foreignland, 0.4-0.55 g/kg/meal is 0.18-0.25 g/lb.  It seems like when I’ve seen this recommendation regurgitated it’s usually stated that you need to eat 0.25 g/lb/meal to maximize muscle protein synthesis which is the high end of the above values.  This is to be done four times per day.

For a 200 lb (90ish kg) athlete, that’s 40 grams of protein 4 times per day for 160 g/day or .8 g/lb per day.  It’s a little more than 1.6 g/kg but that’s just a rounding thing.

Ok, so that’s the claim, what are the problems with it?

Protein Source

The first issue with most of the studies done to date is this: for methodological reasons, skeletal muscle protein synthesis rates are typically measured after the provision of whey protein, a very  fast digesting protein.  And it is typically given by itself with no other nutrients.

So the researchers will take subjects and put them through some amount of training and then give them 20 or 40 grams of whey protein after training to see what happens to MPS.  And what is often seen is that 20 grams gives a maximal response compared to 40 grams.  Or the difference between the two is too small to matter.  In one study, 40 grams gave an 11% greater response in MPS than 20 grams.  So doubling the intake had a very small effect and 20 grams might as well give a maximal effect.

But using isolated proteins like this is a problem especially when they are fast digesting (since we’ve known forever that they are handled differently in the body than slower proteins).  Because the amount and type of protein isn’t the only factor which determines the overall anabolic effect of a protein.

Food exists within a matrix with other nutrients impacting on how that food is utilized.  Other nutrients such as fatty acids, fiber, carbohydrates along with the form of food are all relevant.  Studies need to examine whether other nutrients (not just carb drinks) impact on either the ideal protein or optimal amount per meal.  Using isolated proteins is all good and well to provide dietary control in research but it is not ecologically sound to the real world (yes, I know some consume whey protein alone immediately after training).

To this I might add that typically protein synthesis is measured for relatively short periods after training, a few hours.  Certainly fast proteins are probably done having their effect within that time but solid proteins digest over 4-5 hours to begin with.  Measuring for long enough to get a full picture is important (and yes, some of the studies might have, I’m not delving into them one by one for this).

The Training Protocol

Let me note that the studies doing that are usually in response to things like 4 sets of leg extensions (not all studies do this and one used a more meaningful workout of leg press, leg extension and leg curl for 4 sets each).  One study I reviewed on the site found that doubling post workout protein from 20 to 40 grams did have some benefit after a whole-body workout.

But the increase in MPS was only about 20% for the 40 grams versus the 20 grams, it wasn’t anywhere close to double.  But training more muscle mass in that workout did mean that more protein generated a larger response.  It just wasn’t proportional to the increased amount of protein as you might expect.

On the one hand we might question what real-world benefit is for that 20% increase when protein intake is doubled.  On the other, every little bit helps over time, right?  On the third hand, if you’re not doing a full-body workout does this finding matter?  On the fourth hand (huh?), who only does like 4 sets of leg extensions in a workout (like some studies) before calling it a day?  We need work looking at more complex workouts.  Even if it’s just a more real world leg workout like 4 sets of leg press and 4 sets of leg extensions or something (again, some studies have used this type of workout).

Of perhaps more interest, in this study differences in lean body mass between the subjects didn’t seem to have an impact: bigger and smaller guys both got the same response from the same absolute amount of protein, I have no idea why.  You’d expect bigger guys with more muscle to be able to use more protein but that didn’t seem to be the case.  I could sort of hand-wave some speculative reasons but it’s not that important.  It was what it was.

The above two issues are really the simple ones and, to a first approximation, don’t matter that much.  Because for the most part, it’s the next two issues, and especially that last one that make the recommendation of 0.25 g/lb/meal to maximize protein synthesis so unbearably stupid as a conclusion about protein requirements.

First let me remind you of the recommendation

Consume ~0.4 g/kg body mass (i.e., 0.24 plus 0.06 with protein added to account for the influence of other macronutrients in meals and protein quality), to maximally stimulate muscle protein SYNTHESIS [my emphasis] following a period of rest or exhaustive resistance exercise.

That capital word is the key here.  The above recommendation is the amount to maximize skeletal muscle protein SYNTHESIS.

Muscle Protein Breakdown

The next to last issue has to do with the concept of muscle protein breakdown or MPB which is exactly what it sounds like: it is the rate at which muscle protein is being broken down.  Now at any given time muscle is being both synthesized and broken down.  MPS and MPB represent the rates of the two processes.  And it is the balance of these two processes that determine the ultimate change in muscle mass.  This can be written descriptively as

Change in Muscle Mass = MPS – MPB

If MPS > MPB over a long enough time, muscle is gained.  If MPS = MPB, there will be no change.  If MPB > MPS, there will be a loss of muscle.   It’s no different than anything else in the body, such as bodyfat.  If you’re storing more fat than you’re mobilizing/burning, you gain fat.  If you’re mobilizing/burning more than you’re storing, you lose fat.  If you’re laying down more calcium in bone than you’re losing you gain bone, lose more than you lay down and you lose bone.  Get it?  It’s the balance of synthesis and breakdown that determines the final effect.

And in premise that means that you could achieve a net increase in muscle mass in a number of ways.   So let’s say that everything is in balance and both MPS and MPB are 10% or whatever.  If MPS stays the same and you reduce MPB by 5% net protein balance is now +5%.  If MPS goes up by 5% and MPB stays the same, net protein balance is also now at +5%.  If MPS goes up by 5% and MPB goes down by 5%, net protein balance is now +10%.  These numbers are made up.

But what that means it that you can’t just consider MPS when looking at the potential impact of dietary protein (or any other nutrient) on muscle mass.  You can’t just ignore MPB in the equatino.  Yet it often is.  Why?

Well, MPB is methodologically very difficult to measure. I couldn’t begin to explain the details of why it’s so difficult, it just is.  Some studies seem to be using proxy markers of late, genes or some breakdown byproduct to try and infer that protein breakdown has increased.  But direct measurement is a problem.  To which I say “So what?”

Just because some physiological process is difficult to measure doesn’t mean we get to just ignore it in all of this.  But that seems to be what’s going on for the most part: it’s hard to measure so we’ll just pretend it doesn’t matter.

Now some may remember the debate over whether or not protein and carbs post-workout was superior to protein alone.  The basic idea, and I’ve written about this before is that protein primarily stimulated protein synthesis while carbs (via insulin) inhibited protein breakdown which is true.  But this was counter-argued variously.

One point, possibly true, is that protein raised insulin sufficiently post-workout to inhibit MPB.  I suspect it depends on the protein source but no matter, there is truth to this.   Mind you, this doesn’t change a damn thing and still points out that protein intake has an impact on MPB.  And that means that we need to know what the impact of varying amounts of protein has on MPB.

A second argument was that MPB or the carb/insulin effect wasn’t important was that MPB was only changing by 30% post training.  The conclusion was essentially that MPS was the primary driver on net protein balance and MPB could be safely ignored because it’s contribution was small.  And well, I think that’s a dumb conclusion.

I don’t personally think 30% is a small difference in overall protein balance and if consuming more dietary protein has that impact (and we don’t know that it does, the study linked compared protein to protein/carbs) that’s significant.

Note: A counter-counter argument is that inhibiting protein breakdown at all might IMPAIR adaptations to training by reducing protein turnover but I’m not getting into that.

It doesn’t change the fact that we don’t get to ignore MPB because it’s hard to measure and we don’t really know how varying dietary intakes or types of protein does or does not impact on MPB.  And note here I am talking very specifically about muscle protein breakdown.

Which leads me into what I think is the biggest problem with this whole recommendation and why I think it’s so utterly stupid.

MPS is an Idiotic Endpoint to Use

Honestly, I could have ignored all of the previous issue and just written about this one because it’s the big one, the big problem with the whole recommendation.   It also baffles me that supposed protein experts would miss what I’m about to explain in terms of why I think MPS is just a myopically wrong and stupid endpoint to use to make any sort of meaningful recommendation.  Let’s look at why.

We can divide the body up simply into fat mass (FM all of your body fat) and fat free mass (FFM).  FFM is synonymous enough with lean body mass (LBM) which I’ll switch to here.  Now LBM is everything that’s not fat.  That means brains, skin, water, electrolytes, bones, organs, connective tissues, muscle and probably other stuff I’m forgetting.

Many of those contain or are made up of protein: skin, hair, fingernails, organs, connective tissues, skeletal muscle all contain protein in some amount.  Other things in the body are made of protein too.  Like the peptide hormones such as Growth Hormone (GH) or IGF-1; they are synthesized from amino acids.

Now here’s a fun fact I’ve mentioned before: in men, skeletal muscle makes up about 40-45% of total LBM (in women it’s about 5% lower due to women having more organ mass) although it can go slightly higher in very elite athletes (who are likely on drugs) who have maximized their muscle mass and are relatively lean such that they aren’t carrying a bunch of non muscle mass LBM (i.e. water, glycogen, etc.).

Now, if only 40-45% of total LBM is skeletal muscle, that means that 55-60% of the total LBM on a person’s body is NOT muscle mass.  And of that 55-60%, at least some of the LBM is made up of or utilizes protein in some form or fashion.  I won’t even try to estimate what percentage but some of it.  So if you have 180 lbs of LBM, about 40-45% or 72-81 lbs of it is muscle.  The other 99-108 lbs is NOT muscle.

So I ask the following questions?

Does the rest of the protein using LBM in the body somehow not matter?  Do the liver or heart or connective tissues somehow not need protein to support them on a day-to-day basis?  How could they not?  All tissues of the body are in a relatively constant state of turnover (breakdown and resynthesis) and none of those processes are 100% efficient.

We know that if dietary protein intake is too low for too long those tissues start to break down so of course they have their own protein requirements.  How much?  I have no idea.  But it’s sure as shit not zero.

Adding to that, is it possible that athletes are stimulating adaptations in those tissues with heavy training that are further increasing their protein requirements?  Tendons and ligaments for example.   Now we know that those tissues adapt very slowly and I wouldn’t say that their protein requirements are high.

But we also know that providing the right type of protein (gelatin) prior to training increases protein synthesis in them (I wrote about this in my Optimal Nutrition for Injury Recovery booklet).  A recent study found that collagen protein increased LBM gains in response to training although it appears to have been an increase in connective tissue rather than muscle per se.  So clearly more protein can help in this regard.  As I wrote in the protein book so very long ago:

As mentioned in Chapter 1, there are a number of additional metabolic processes important to athletes that are likely to be up regulated through athletic training (15). All of these are likely to require increased amounts of dietary protein although what amount is currently unknown. It’s possible that the amount of protein required to maintain nitrogen balance (or generate a positive balance) is still insufficient to optimize all aspects of metabolism important to athletes (15).

My point being this: more than just skeletal muscle requires protein both to optimize protein synthesis and reduce protein breakdown in all humans. This might be further impacted by all of the different adaptations that are stimulated in hard training athletes. And given these facts I ask the following:

Why in the everloving fuck would someone use SKELETAL MUSCLE MPS alone as
the endpoint criteria for per meal or per day protein recommendations? 

It’s truly baffling to me.  Skeletal muscle makes up less than half of total LBM and much of the remainder clearly needs some amount of protein for optimal function even if we don’t have good numbers for it.    That’s still ignoring the role of protein breakdown in net balance.

And yet somehow supposed experts in protein metabolism have fixed on a singular end point of skeletal muscle protein synthesis to make overall recommendations for daily protein intake.  As if somehow those other tissues and protein breakdown aren’t relevant.  Like I said, baffling.

I’m not making some incredibly esoteric argument here.  This is basic physiology: protein breakdown matters and skeletal muscle isn’t even half of total LBM in most people.  And those simply facts are being ignored by a great many people.

Because it’s clear that if you don’t ignore those things, that you’re a researcher who actually understands basic physiology and protein metabolism, a different picture entirely develops.  Robert Wolfe’s group for example.

In one study, Wolfe’s group measured WHOLE BODY protein synthesis, protein breakdown and net protein balance.  provided either 40 or 70 grams of protein in a single meal.  It provided that protein primarily as beef patties.  So not only did it measure all three relevant parameters, with two different protein intakes, it used whole food rather than an isolated protein.

And what it found was that net protein balance was in fact higher at the higher protein intake. And this was due to the effect of increased protein in reducing protein breakdown without a further increase in protein synthesis.

So yeah, even here there was a plateau in whole body protein synthesis at the 40 g/meal level.  But more protein still had a positive effect by decreasing protein breakdown.  And while some dismissed this study because “It was whole body instead of muscle” it doesn’t matter so far as I’m concerned.  Skeletal muscle isn’t all that matters in terms of protein requirements on a day to day basis.  You can’t just ignore the other tissues to fixate on what amounts to 40-45% of total LBM in most people.

So rather than the supposed anabolic plateau that was determined by fixating on protein synthesis in a single tissue,  Wolfe’s group has basically found that with increasing amino acid availability, there is essentially a linear increase in protein balance in the body.  

As they rather clearly conclude in that paper (and the link goes to a free full text if you want to read it):

Extrapolation of the FSR [fractional synthetic rate] response to the conclusion that there is a maximal amount of protein in a meal that can stimulate net protein anabolism is not justified. In our opinion, the preponderance of evidence indicates that the more protein in a meal, the more anabolism will be observed. This perspective is supported by a recent publication in this journal () in which consumption of 80% of the 1.5 gram protein/kg BW/day in a single meal was more anabolic than spreading the same amount of protein intake throughout the day. If the limit to the maximal anabolic response of 30 gram/meal, the approach of providing most protein in one meal would have been unsuccessful in achieving the optimal anabolic response.

Now, no, more protein per meal doesn’t mean that muscle will grow faster.  But that’s not the issue here.  People are making per meal protein recommendations to athletes or bodybuilders based on the singular endpoint of skeletal muscle protein synthesis which is just moronic on top of being baffingly wrong.

Consuming 0.25 g/lb four times per day might maximize muscle protein synthesis.  It just happens to leave all of the other LBM tissues that need protein without sufficient amounts on top of doing nothing to maximally reduce protein breakdown.

And that’s why this current and oft repeated protein recommendation is wrong: it’s being based on the measurement of a single endpoint (protein synthesis) in a single tissue (skeletal muscle).  And that simply does not represent the totality of the system on any level.

And repeating myself, it’s baffling that supposed experts on this topic would miss such a brutally obvious fact about human physiology.

Protein Requirements for Athletes

So how much is optimal?  Well as the above suggests, there is no practical limit to daily or even per meal protein intake but I don’t want people reading this to think I’m suggesting ALL THE PROTEIN.

At some point, protein intake probably gets excessive in a practical sense or simply crowds out carbohydrates and fats (or becomes too damn unaffordable).   So there’s some happy medium between the asinine recommendation and eating all the protein.

In the Protein Book I referenced Wolfe and Tipton stating:

Getting into recommendations, the paper points out that a daily protein intake of 2.5-3.0 g/kg (1.1-1.4 g/lb) for strength/power athletes is not harmful, may give small but important performance improvements over the long-term, and will more than cover any needs for protein synthesis (it’s conceivable but understudied that anabolic steroids could increase requirements even further). Any excess will simply be oxidized off in the first place; I’d note again that some researchers feel that the end products of AA oxidation may contribute to the overall anabolic drive in the body.

And I’d stand by that at least for high level athletes looking to optimize all potential aspects of performance including non-muscle tissues that utilize protein.  Assuming that it doesn’t prevent sufficient carbohydrate and fat intakes, that level of intake has no downsides and may have long-term benefits (many of which would not show up in short-term studies to begin with).

Mind you, this is truly for high-level athletes and wouldn’t really apply for the general recreational trainee or what have you.  In that situation, 2.2 g/kg or the standard 1 g/lb is likely to be more than sufficient.    Why not give a lower value? Well in practice if the average person shoots for 1 g/lb they will probably fall short to begin with and end up lower than that.  Give them 0.8 g/lb (1.6 g/kg) and they will end up even lower and potentially run into problems in terms of sub-optimal protein intakes.

Irrespective of that, I think I’ve shown that the idea that using muscle protein synthesis as the endpoint to determine per meal or per day protein intake maximums is simply asinine.  I’m still baffled.