When it comes to the accretion of new muscle mass, protein intake is one of the primary variables to consider. Common discussions range from how much protein, protein source and bioavailability, refractory periods, protein distribution and more. This article will give a brief distillation of the current available evidence and offer clear and concise recommendations to optimize protein distribution throughout the day and maximize your results.
Protein serves various functions in the body including but not limited to growth and maintenance of tissus, catalyze biochemical reactions, recovery from injury, normal immune function, etc (1)(2)(3)(4). But of particular interest is its role in the synthesis of skeletal muscle. Muscle protein synthesis (MPS) is the process by which our bodies synthesize new muscle tissue. It’s a primary variable that galvanizes tissue remodeling (5).
Muscle protein breakdown (MPB) is an oppositional effect whereby muscle proteins degrade. This occurs through autophagy, and calpain and the ubiquitin-proteasome systems (6). The balance between these two processes determined whether an individual will gain, maintain, or lose muscle mass. When the rate of MPS outpaces MPB new muscle is accrued. When MPB outpaces MPS, muscle loss is observed.
A 2019 paper by Iraki et al. established recommendations for natural bodybuilders in the offseason. The authors reiterate what the larger body of evidence suggests which is that total protein intake is a more significant determining factor in the development of new muscle mass when compared to protein distribution (7). Currently the research suggests a protein intake of 1.6-2.2g/kg per day is sufficient to optimize muscular gains (7). However, when protein, calories, and any resistance exercise protocol are standardized, we still see a slight benefit when protein distribution is optimized throughout the day.
One of the more obvious reasons for this is the refractory period of MPS. The leucine threshold describes the amount of leucine required within a protein feeding to maximally stimulate MPS (8). Protein quality and bioavailability isn’t the subject of this article, but generally what’s observed is animal based protein seems to be superior to plant based proteins in most cases. However, there are several non animal-based protein sources that are high quality. If you’re interested in diving into this topic you can get started by reading this paper, and this one, and this one. But I digress.
Assuming a sufficient quantity of protein is consumed we maximize the MPS response (roughly 20-40g). This response comes with what’s known as the “muscle full effect” as described by Schoenfeld et al. in his 208 paper. Essentially once MPS is maximally stimulated there is a refractory period by which MPS can’t be maximally stimulated again (9).
A 2017 paper by Kirksick et al. found “Ingesting a 20-40 g protein dose (0.25-0.40 g/kg body mass/dose) of a high-quality source every three to 4 h appears to most favorably affect MPS rates when compared to other dietary patterns and is associated with improved body composition and performance outcomes.” (10).
So does protein distribution affect accretion of muscle mass? Yes it does, but the effect is small. Although I would caution against assuming that small is synonymous with not meaningful. It’s value is relative to the individual and their goals. Hypothetically speaking a 1% increase in hypertrophy for an elite bodybuilder may be the difference between 1st and 5th place. For the average individual the extra effort may not be worth the relatively small effect on results. At the end of the day it’s up to each individual to determine whether or not the investment is worth it. Good luck!