Anabolic Response to Protein Ingestion Post-Workout
Trommelen: Cell Reports Medicine: mTOR, protein, digestion absorption bioavailability, autophagy, intermittent fasting, time-restricted feeding, meal frequency
Previous literature and talking points have suggested that the rate of protein synthesis (recovery) reached a plateau after ingesting a certain amount of protein — approximately 20 - 25g.
The logic that often follows is that “eating more than 25g of protein / serving is ‘wasted.’” That never made a lot of sense to me because it sounded like saying, just because we can only go 25 mph, we only have 25 miles to go.
The rate at which we accelerate has no bearing on how far we have to go to complete a journey — or repair a certain tissue.
Highlights:
Postprandial protein anabolism remains elevated during prolonged hyperamnioacidemia.
Protein ingestion has a negligible impact on whole-body animo acid oxidation.
Muscle protein autophagy is not modulated by protein ingestion.
Exogenous amino acids are the main precursors in postprandial protein accretion.
“These findings demonstrate that the magnitude and duration of the anabolic response to protein ingestion is not restricted and has previously been underestimated in vivo in humans.”
Trommelen, J., Van Lieshout, G. a. A., Nyakayiru, J., Holwerda, A. M., Smeets, J. S. J., Hendriks, F. K., Van Kranenburg, J. M., Zorenc, A. H. G., Senden, J. M., Goessens, J. P. B., Gijsen, A. P., & Van Loon, L. J. (2023). The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans. Cell Reports Medicine, 4(12), 101324. https://doi.org/10.1016/j.xcrm.2023.101324
This article is an important reference to combat the claims that humans should reduce or eliminate their meat consumption. What we see in this paper is that “protein ingestion rapidly increased plasma amino acid concentrations in a dose-dependent manner.”
The authors noted that ingestion of 100g of protein resulted in a greater rise in circulating plasma amino acid concentrations, which remained higher throughout the entire 12-hour postprandial period.”
The first part is obvious, that ingesting protein resulted in higher amino acid concentrations in blood, and that the response was dose dependent — more protein, more animo acids.
It seems my gas-mileage metaphor is accurate because we see that even if protein synthesis (from blood to muscle tissue) is rate limited, blood levels of amino acids remain elevated for a longer period of time if a larger bolas of protein is ingested. That is, we filled up the gas tank, but can only travel so fast.
“Exogenous dietary protein derived amino acid appearance into the circulation was significantly higher in (100g protein ingestion) when compared to (25g protein ingestion)… In contrast, the endogenous tissues protein-derived amino acid rates of appearance into the circulation did not differ between treatment.”
“Filling up the gas tank” or “having further to go” is important when we consider chronic recovery (day to day) rather than acute (within 4 hours after protein consumption). “… protein synthesis rates were only ~20% higher during the early 0-4 hour period, but ~40% higher during the subsequent 4-12 hour period in (100g protein ingestion) when compared to (25g protein ingestion).”
Summarily then, “the postprandial increase in muscle protein synthesis rates following ingestion of a large amount of protein (100g) was sutained well beyond the transient anabolic and catabolic myocellular signaling response to feeding.”
Also important are the author notes that meal frequency and time restricted feeding do not impair muscle mass maintenance, assuming that total protein intake is adequate (e.g. for the purposes of muscle protein synthesis you do not need to eat every 2-3 hours; though insulin may be a different story).
The authors also note a limitation of testing “healthy subjects” in this study; “It has been well established that the anabolic sensitivity to amino acids is lower in individuals that are more clinically compromised and / or have lower phsyical activity levels.”
What that means is that metabolically and physically compromised — diabetic and / or obese — people have more difficulty synthesizing protein.
In conclusion, while the rate of protein synthesis and use of amino acids from blood to muslce tissue may reach it’s limit after consuming 25g of protein, total protein intake or a large bolas of 100g of protein delivers more total amino acids and allows for synthesis to continue for a longer duration (e.g. 4 hours versus 12 hours) at the same maximal rate.