How much protein can your body use for muscle growth in a single meal?
Take-aways
Total daily protein is far and away the main thing to focus on when it comes to building muscle.
A large protein feeding of 100 grams at once, post-training, stimulates myofibrillar protein synthesis for at least 12 hours, suggesting a large protein feeding before bed at night may be advantageous.
While there may be a slight benefit to having 3-5 smaller protein feedings per day for muscle growth, you will still see great gains even if you only have 1-2 large protein feedings per day, provided you achieve a sufficient overall protein intake (around 1.6g/kg of bodyweight/day).
A common idea in the fitness industry is that your body can only use so much protein in a single meal. Indeed, some research suggests the “muscle protein synthetic” (or, roughly speaking, your body’s muscle growth response to a protein feeding) peaks around 40g of protein ingested. In fact, ~20-25 grams has often been shown to increase the muscle growth response to a similar extent as 40g. Above this very low threshold, the fate of ingested protein appeared unclear; at least, it was assumed not to contribute to further muscle growth.
However, this idea of a hard threshold for protein synthesis at only 40 grams stands in contrast to the physiology of many other animals. Many serpents, for instance, only feed infrequently. Their meals are generally around >25% (!) of their own bodyweight. Following this, their protein synthetic responses often last around 10 days.
So, what’s the catch? Do we differ wildly in our physiology, or is there more to how we use protein in a given meal?
This is where a recent study by Trommelen and colleagues comes in. The manuscript was a whopping ~50 pages, so I’ll keep to the main take-aways.
Previous studies had only looked at protein amounts up to ~40 grams and timecourses of ~6 hours after feeding. Using new tracer technology, the authors were able to assess differences in muscle growth response over 12 hours from a protein feeding of either 25 or 100g of milk protein after a training session.
Participants came to the lab, having fasted for the last ~9 hours. They performed a resistance training session, followed immediately by either 0, 25 or 100g of protein. The authors measured a variety of muscle-growth related variables both before training (at rest, unfed) and in the 12 hours after training/feeding. For the first time, a study looked at muscle protein synthesis responses with a very high dose protein feeding and over 12 hours.
The muscle growth response per hour, averaged across 12 hours post-training. Endogenous AA represents the body using amino acids that were already present in the body pre-feeding for muscle growth; exogenous AA represents the body using the protein ingested for muscle growth.
As you can see above, 100 grams of protein resulted in a greater muscle growth response when averaged over the following 12 hours than 25g protein. This suggests that the ceiling for “effective” per meal protein is not as low as 40 grams. However, the story gets more interesting when you break things down by time.
Cumulative incorporation of protein ingested into skeletal muscle by group (black dots = 100g condition, grey dots = 25g condition).
When you look at various timepoints, a different story emerges. Specifically, in the 4 hours following training + feeding, 25 and 100g of protein result in a similar incorporation of protein into muscle (though the 100g group was still superior). However, the difference became increasingly apparent between 4-12 hours after training. During this time, the incorporation into skeletal muscle was essentially done for 25 grams, but continued for the 100 grams group.
Release of amino acids into bloodstream over 12 hours post-feeding (black dots = 100g condition, grey dots = 25g condition).
Why?
Previous studies had likely failed to find a benefit of >40 grams of protein in a single feeding due to the timeline of measurement being too brief. Indeed, when you look only at the 4 hours post-feeding, both 25 grams and 100 grams saw a response and the difference wasn’t too large, considering we’re talking about a 4x difference in protein intake. Thus, when comparing 40 and 20 grams, differences are typically even smaller. However, with this study going past the usual-6-hour timeline measured, we can see that when consuming 100 grams, amino acids gradually get released into circulation in the bloodstream, incorporated into skeletal muscle and eventually stimulate myofibrillar protein synthesis over at least 12 hours. Ultimately, this makes sense; your gastrointestinal tract needs time to digest food through the intestines, leading to a gradual release and titration of amino acids into your bloodstream when you consume a large amount of protein/food at once.
It’s worth noting that myofibrillar protein synthesis and muscle growth are not perfectly correlated. Whenever interpreting this research, keep this in mind.
