Is The Timing of Daily Protein Intake That Important, and What About The Dose?

Skeletal muscle tissue is in a constant state of turnover which allows muscle tissue to remodel by replacing damaged proteins and changing the muscle tissue protein composition.

Muscle protein synthesis rates have a higher capacity to fluctuate compared to muscle protein breakdown rates, therefore postprandial (i.e. after eating) muscle protein balance is assumed to be largely governed by changes in muscle protein synthesis rates⁽¹⁾.

Protein ingestion and muscle contraction are the main drivers in enhancing muscle protein synthesis rates⁽²⁾.

Previous dose-response studies have indicated that consuming 20-25 grams of protein is adequate to maximize post-exercise muscle protein synthesis rates in healthy, young adults and there is no further increase in muscle protein synthesis rates when larger amounts of protein are consumed⁽³⁾.  

It’s suggested that higher protein intake doesn’t further increase anabolic signaling and excess amino acids are thought to be oxidized. The current recommendations are to distribute protein intake evenly throughout the day, with each main meal providing no more than 20-25g protein⁽⁴⁾.  

There are some that think this advice is not consistent with animal research in which the feeding practices of many animals in nature consume large amounts of food infrequently⁽⁵⁾.

To investigate this question; a recent study aimed to comprehensively assess the time resolution of postprandial protein handling in response to the ingestion of moderate and large amounts of protein (0, 25, and 100 grams) following exercise on a whole-body, muscle-tissue, and myocellular level in vivo in humans⁽⁶⁾.

Major Findings

This research demonstrated that the anabolic response to protein ingestion has no apparent upper limit in magnitude and duration in vivo in humans. It was shown that protein ingestion results in a dose-dependent increase in dietary protein derived amino acid availability and a concomitant increase in muscle and whole-body protein synthesis rates (see figure below).

Figure: Illustration of the postprandial protein handling 6 Illustration of study results. Following protein ingestion, exogenous-protein-derived amino acids are released into the circulation, resulting in increased plasma amino acid concentrations. Subsequently, amino acids are taken up by tissues, resulting in an increase in whole-body protein synthesis and net balance, with negligible impact on amino acid oxidation. Protein ingestion does not expand the muscle free amino acid pool but stimulates (de novo) muscle protein synthesis rates. Postprandial myocellular protein signaling and gene expression become dissociated from the sustained postprandial increase in muscle protein synthesis rates. The magnitude and duration of the metabolic responses are proportional to the ingested amount of protein.

The postprandial increase in plasma amino acid availability has a negligible effect on whole-body protein breakdown or postprandial amino acid oxidation rates. The postprandial increase in muscle protein synthesis rates following ingestion of a large amount of protein (100 grams) was sustained well beyond the transient anabolic and catabolic myocellular signaling response to feeding.

This data provides important mechanistic insight into the ongoing controversy of the impact of different feeding strategies to optimize muscle tissue anabolism and/or metabolic health.

It is essentially believed that consuming about 20 grams of protein maximizes post-prandial (post meal) muscle protein synthesis rates at rest and during recovery from exercise in healthy, young adults. The limitation is that all previous research in this area utilized a small range of protein intake (≤ 45g) and relative short assessment periods (≤ 6h).

To investigate potential upper limits and/or sustained elevation of post-prandial protein metabolism, this research provided the proposed optimal amount (25 grams) and the largest amount of protein they considered feasible to consume in a single meal (100 grams) and evaluated post-prandial protein handling throughout a prolonged 12-hour assessment period. 

Findings demonstrated higher plasma, muscle, and whole-body protein synthesis rates following the ingestion of 100 grams of protein when compared to 25 grams of protein and placebo, respectively.

The greater metabolic responses were present during the early post-prandial phase (0-4 hours) but were even more pronounced during the prolonged post-prandial phase (4-12 hours).

Another important consideration is that the historic recommendations were for an equal distribution of daily protein requirements over the main meals to support muscle anabolism⁽⁴⁾.

These recommendations are based entirely on the notion that the muscle protein synthetic response to ingestion of a single bolus of protein has a ceiling and is short lived. The current findings provide evidence to support more flexibility in feeding patterns aimed at enhancing muscle anabolism. Specifically, this research indicates that the ingestion of a single large amount of protein is followed by a prolonged anabolic response, which would obviate the need to consume another protein-rich meal in close proximity.

This may explain why time-restricted feeding patterns do not seem to compromise muscle mass maintenance⁽⁷⁾.

An important caveat to keep in mind is that this research was done on healthy, young men following a bout of whole-body resistance exercise.

It can not be determined if these results can be extrapolated to other populations and/or conditions. It is well established that the anabolic sensitivity to amino acids is lower in individuals that are more clinically compromised and/or have lower physical activity levels⁽⁸⁾. 

While there are data that suggest that a blunted anabolic response to feeding in these populations can be compensated for by the ingestion of larger amounts of protein⁽⁹⁾, it is possible that these more clinically compromised individuals may experience a ceiling response in the magnitude and/or duration of the anabolic response to protein ingestion.

Summary

This work highlights that tissues have a much higher capacity to incorporate exogenous-protein-derived amino acids than previously assumed and that the duration of the postprandial period is proportional to the size of the ingested meal.  

Highlights of this research are:

• - Postprandial protein anabolism remains elevated during prolonged hyperaminoacidemia
• - Protein ingestion has a negligible impact on whole-body amino acid oxidation.
• - Muscle protein autophagy (i.e., cell degradation) is not modulated by protein ingestion.
• - Exogenous amino acids are the main precursors in postprandial protein accretion.

This is very important research and sheds light on the subject of how to maximize protein intake in order to enhance anabolism and increase muscle mass.  It offers more flexibility to those that prefer time-restricted feeding patterns and doesn’t require a stringent eating pattern throughout the day.  

Ideally, you would get your 100g of protein from real food. But depending on your schedule, it may be challenging to sit down and eat a big enough meal that would hit that goal directly after you train, which is where supplementation can help.

STEEL has an entire line of delicious whey and plant-based proteins that contain all of the essential amino acids. There are over a dozen flavors to choose from so no matter your taste, you'll find something you love.

If you're looking for a delicious way to ensure you get enough protein after your training sessions, you can find all the delicious flavors they offer here.

References:

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