THE MYTH AND THE TRUTH ABOUT PROTEIN ABSORPTION
As we all know, there are plenty of bro-science myths in the fitness industry that have little to no scientific merit.
In fact, one of the most popular myths in the body recomposition space is the idea that your body can only absorb a certain amount of protein from a single meal.
If this is true, the rumored implications of eating more protein than your body can absorb in a single sitting are, at best, that you’re wasting precious air-fried tofu, or, at worst, that you’re actually storing said excess protein as unwanted body fat.
But again, these are just whispers in the wind.
What does the current body of scientific literature really have to say about these alleged protein absorption limits within a single meal?
Our current understanding is this: Your body can absorb nearly an unlimited amount of protein into the bloodstream.
But even this statement warrants further explanation in the context of a body recomposition goal.
My guess is that no one reading this article is reading this article because they’re interested in general protein absorption.
If you’re here, you’re likely here because you want to build a noticeable and respectable amount of lean muscle, right?
And in that pursuit, you want to know the optimal amount of protein to consume per meal to maximize your training efforts.
To that end, the more accurate question that actually does have scientific support is this:
How much absorbed protein can your body use from a single meal for the purposes of building muscle?
Or, in more technical terms, what amount of protein maximally stimulates the postabsorptive rates of myofibrillar muscle protein synthesis?
Interestingly enough, research has long suggested that there is, in fact, a ceiling on muscle protein synthesis that has been termed the “muscle full effect.”
In other words, there is only so much protein that your body can use at a time to rebuild muscle.
WHAT IS THE PROTEIN ABSORPTION CEILING?
Obviously, there must be some upper limit regarding the amount of protein your body can process and use for rebuilding and growing muscle tissue, right?
Your body almost certainly can’t utilize hundreds of grams of protein at a time for muscle growth. If it could, we’d all be slamming protein shakes into oblivion while gaining muscle at unregulated rates.
The question is, how much protein will cause you to hit this acute ceiling? And how can we use that information to optimize our own protein consumption?
Well, according to numerous studies conducted over the past twenty years, the amount of protein that represents that ceiling isn’t very high. For more information, see these case studies from 2004, 2008, 2012, and 2015.
A 2014 study published in the American Journal of Clinical Nutrition determined that just a 20-gram dose of high-quality protein was sufficient for the maximal stimulation of postabsorptive rates of myofibrillar muscle protein synthesis in men with resistance-training experience who weigh around 80 kilograms.
The researchers concluded that any amount of protein consumed beyond 20 grams would get oxidized (meaning the amino acids would be burned for energy) or filtered out by the kidneys and excreted from the body in urine.
However, there are several important factors that this study did not analyze.
For example, while the average male fitness enthusiast probably does weigh around 80 kilograms, there are plenty of guys with substantially more muscle mass.
This begs a few questions:
Would heavier athletes with more muscle mass benefit from more muscle mass?
Does the thoroughness, complexity, and intensity of an individual’s workout warrant additional consideration of optimal protein consumption?
Do protein recommendations change as we get older?
These are questions we will explore in a moment.
WHAT AFFECTS YOUR BODY’S PROTEIN ABSORPTION CEILING?
Beyond total muscle mass, there are at least three other major factors that have a direct effect on an individual’s protein absorption ceiling:
Their total amount of muscle mass
The amount of muscle mass they train (full-body versus body part isolation)
Their age
Let’s take a look at these factors in more detail.
FACTOR 1: TOTAL MUSCLE MASS
In 2015, researchers from McMaster University used a linear regression analysis on previous protein research, which ultimately led them to recommend a target intake of 0.4 grams of protein per kilogram of body weight per meal to maximally stimulate muscle protein synthesis.
That target is equal to 0.18 grams of protein per pound of body weight per meal.
Their research determined that consuming protein beyond this dose would result in no further stimulation of muscle protein synthesis.
According to their recommendation, a person who weighs 185 pounds should aim to consume 33 grams of high-quality protein per meal to maximally stimulate muscle protein synthesis.
Their findings have proven to be very helpful in determining the optimal protein feedings for a wide range of individuals with different body types. Rather than offering unhelpfully generic protein recommendations to a diverse audience, we can use these findings to more finely calibrate protein consumption on an athlete to athlete basis.
That being said, protein recommendations based on lean muscle mass would hypothetically be the optimal measurement over protein recommendations based on total body weight, but this research does not yet exist.
Keep in mind too that these protein recommendations are most relevant for leaner individuals, which means these recommendations can be lowered for individuals who carry a considerable amount of body fat.
For women, we might consider “lean” in this context to mean a body fat percentage of 24% or less. And in men, we might consider “lean” to be below 16%.
FACTOR 2: THE AMOUNT OF MUSCLE MASS YOU TRAIN
Over the years, one of the most notable design flaws in a host of “muscle full effect” studies has been the lack of practicality among the training programs the study participants were instructed to execute.
Until recently, nearly all of the studies incorporated isolation-based training programs. And, in many cases, these exercise programs were limited to lower body training exclusively.
For example, in the 2014 study that determined a 20-gram dose of protein is sufficient to maximally stimulate muscle protein synthesis, the subjects only performed one lower body workout that included just two exercises: leg presses and leg extensions.
The problem?
This isn’t how most people train in practice, and it’s certainly not how dedicated bodybuilders and/or physique enthusiasts design their training programs. In fact, completing a workout consisting only of leg presses and leg extensions would only really make sense in context of a very high-frequency training split or when extremely time-restricted.
Fortunately, in 2016, a team of researchers from the University of Stirling, McMaster University, and the University of Birmingham sought to correct this flaw by designing a “muscle full effect” study that required subjects to complete a full-body resistance training program.
Their full-body training program included the chest press, lat pull-down, leg curl, leg press, and leg extension.
And although that protocol still wasn't the most ideal training program for improving strength or body composition, it did succeed in pushing all of the major muscle groups to exhaustion, which was a step in the right direction in terms of mimicking traditional bodybuilding and powerlifting training programs.
In other words, the total volume (workload multiplied by repetitions) and intensity of this study’s training program was, in fact, comparable to a heavy, compound-exercise-focused training program that most elite natural bodybuilders and all elite powerlifters follow.
So, what did this study find?
The researchers concluded that the ingestion of 40 grams of high-quality protein following a full-body resistance training workout stimulated a greater muscle protein response than 20 grams in young men with resistance training experience.
The clear takeaway from this study is that the amount of muscle mass you train as well as your training volume and intensity have a substantial effect on how much protein your body needs to rebuild and grow muscle.
In other words, bigger people with more muscle mass will need more protein than smaller people with less muscle mass. Similarly, people who spend more time resistance training will need more protein than people who spend less time resistance training. And lastly, people who train more muscle groups will need more protein than people who train fewer muscle groups.
And this makes good sense.
Consider this same idea through the lens of a car accident analogy. Smaller cars in smaller accidents likely require fewer resources for repair than larger cars in more severe accidents. It would be less expensive to repair an economy car that got into a minor fender-bender than it would be a massive truck that got completely totaled.
On the same basic level, you can apply that same line of thinking to individualized protein needs.
Although the specificity of these implications is nearly impossible to define on an individual basis, it seems as though most people would benefit most from consuming between 20-40 grams of protein per meal in order to maximize the immediate muscle protein synthetic response.
FACTOR 3: AGE
As unfortunate as this may be for anyone moving gracefully into their golden years, anabolic resistance does occur as you age, which simply means it’s asymptotically more difficult to build muscle as you get older.
To illustrate this point, let’s reference a 2015 study that analyzed the relative protein ingested dose response of muscle protein synthesis in younger and older men.
The younger men had an average age of 22 years while the older men had an average age of 71 years.
What did they find?
The researchers determined that the older men needed to consume more protein per pound of lean muscle mass to get the same muscle protein synthesis response as younger men.
If, however, you are reading this as a physique enthusiast in your later years of life, likely the best practical application of this information is simply to err on the higher side of evidence-based protein recommendations.
You could also make the simple adjustment of adding one serving of a high-quality plant-based protein powder to your daily diet to account for any age-induced diminishing returns in muscle protein synthesis.
HOW DO I MAXIMIZE MY PROTEIN INTAKE?
Now that we’ve addressed the nuances surrounding how much protein you should consume per meal to maximize muscle protein synthesis, let’s draw a few practical conclusions.
In summary, most people would be best to follow the succinct advice of Dr. Brad Schoenfeld and Alan Aragon that they published in their 2018 scientific review.
As they put it, “You should aim to consume protein at a target intake of 0.4 grams per kilogram of body weight (0.18 grams per pound of body weight) per meal across a minimum of four meals.”
For a 180-pound athlete, this would be about 32 grams of protein per meal.
For a 150-pound athlete, this would be about 27 grams of protein per meal.
For a 120-pound athlete, this would be about 22 grams of protein per meal.
However, at the end of the day, the most important factors for maximizing muscle protein synthesis are:
Total daily protein intake
Protein quality
If you’re unable to follow the aforementioned advice exactly, simply aim to hit your total daily protein each day while executing a well-designed resistance training program.
Doing this will likely result in most of the benefits recreational lifters are looking to achieve in terms of building muscle.
Summary
One of the most common myths in the fitness industry is that your body can only absorb a certain amount of protein in a single meal for the purpose of building muscle. We refer to this as the protein ceiling.
The current body of scientific literature does show this to be true, but these protein ceilings vary depending on at least three distinct factors:
Total muscle mass
Individuals with more muscle mass will likely benefit from more protein than individuals with less muscle mass.
How much muscle mass is trained and the intensity of that training
Well-designed full-body training systems will likely require more protein than suboptimal training systems focused on fewer muscle groups.
Age
Older individuals tend to need more protein per sitting than younger individuals in order to match the magnitude of the muscle protein synthetic response.
Although the most important considerations for protein consumption are total daily protein intake and protein quality, it seems as though consuming around 0.18 grams of protein per pound of body weight per meal is most optimal when done a minimum of four times per day.
