Protein Intake and Muscle Mass Accretion

Introduction

When delving into the realm of new muscle mass accretion, protein intake emerges as one of the pivotal variables demanding careful consideration. Discussions commonly encompass aspects such as the optimal quantity of protein, protein sources along with their bioavailability, refractory periods, and the strategic distribution of protein throughout the day.

This article aims to provide a concise synthesis of the existing evidence and offer clear - cut, precise recommendations to optimize protein distribution over the course of a day, thereby maximizing the potential for achieving favorable results in muscle development.

Protein’s Role in the Body’s Functions

Protein assumes diverse and crucial functions within the human body. These functions include, but are not confined to:

1. Tissue Growth and Maintenance: Facilitating the growth and sustenance of various tissues in the body (Bosse JD, Dixon BM, 2012).

2. Biochemical Reaction Catalysis: Acting as a catalyst for numerous biochemical reactions, thereby enabling essential physiological processes (Cooper GM, 2000).

3. Injury Recovery: Playing a vital role in the body's recovery from injuries, expediting the healing process (Yeung SE et al., 2017).

4. Normal Immune Function Regulation: Contributing to the normal functioning of the immune system, bolstering the body's defense mechanisms (Li P et al., 2007).

Particularly notable is its role in skeletal muscle synthesis. Muscle protein synthesis (MPS) is the intricate process through which the body constructs new muscle tissue. It represents a key variable that drives tissue remodeling.

Conversely, muscle protein breakdown (MPB) is an opposing phenomenon where muscle proteins undergo degradation. This occurs via processes such as autophagy, as well as through the calpain and ubiquitin - proteasome systems (Kevin D. Tipton et al., 2018).

The equilibrium between MPS and MPB is determinant in dictating whether an individual will experience muscle mass gain, maintenance, or loss:

• When the rate of MPS exceeds that of MPB, new muscle is accumulated.

• When MPB outpaces MPS, muscle loss becomes evident.

Optimize Muscle Mass Gains

A 2019 paper by Iraki et al. formulated recommendations tailored for natural bodybuilders during the offseason. The authors reaffirmed the consensus from a broader body of evidence, highlighting that total protein intake holds greater significance in fostering new muscle mass development compared to protein distribution.

Current research indicates that a protein intake ranging from 1.6 - 2.2 g/kg per day suffices to optimize muscular gains (Iraki J et al., 2019).

Notwithstanding, when protein, calorie intake, and any resistance exercise protocol are standardized, a marginal benefit is still discernible when protein distribution is optimized throughout the day.

One of the more prominent reasons for this lies in the refractory period of MPS. The leucine threshold defines the quantity of leucine necessary within a protein - containing meal to maximally stimulate MPS (Burd NA et al., 2009).

Protein quality and bioavailability, while not the focal points of this article, generally exhibit a trend where animal - based proteins tend to outperform plant - based proteins in most scenarios. However, several non - animal - based protein sources also possess high quality. For those interested in exploring this topic further, relevant papers can be referred to.

Assuming an adequate quantity of protein is ingested, the MPS response can be maximized (approximately 20 - 40 g). This response is accompanied by what Schoenfeld et al. described in their 2018 paper as the “muscle full effect.” Essentially, once MPS is maximally stimulated, a refractory period ensues during which MPS cannot be maximally stimulated again.

A 2017 paper by Kirksick et al. discovered that “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” (Kerksick CM et al., 2017).

So, does protein distribution impact muscle mass accretion? Indeed, it does, albeit to a minor extent. However, it is crucial to exercise caution against dismissing this minor effect as insignificant. Its significance is contingent upon the individual and their specific goals.

Hypothetically, for an elite bodybuilder, a 1% increase in hypertrophy could potentially be the differentiating factor between achieving 1st and 5th place. For the average individual, the additional effort might not justify the relatively small impact on results. The decision of whether this investment is worthwhile ultimately lies with each individual.

References

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2. Cooper GM. “The Central Role of Enzymes as Biological Catalysts.” The Cell: A Molecular Approach. 2nd edition. Sunderland (MA): Sinauer Associates; 2000.

3. Yeung SE, Hilkewich L, Gillis C, Heine JA, Fenton TR. “Protein intakes are associated with reduced length of stay: a comparison between Enhanced Recovery After Surgery (ERAS) and conventional care after elective colorectal surgery.” Am J Clin Nutr. 2017 Jul; 106(1): 44 - 51.

4. Li P, Yin YL, Li D, Kim SW, Wu G. “Amino acids and immune function.” Br J Nutr. 2007 Aug; 98(2): 237 - 52.

5. P. J. Atherton and K. Smith, “Muscle protein synthesis in response to nutrition and exercise.” The Journal of Physiology, Vol 59-.5 1049 - 57.

6. Kevin D. Tipton, D. Lee Hamilton, Iain J. Gallagher, “Assessing the Role of Muscle Protein Breakdown in Response to Nutrition and Exercise in Humans.” Sports Medicine (Aukland, N. Z.). Vol 48, 2018. Suppl 1, 53 - 64.

7. Juma Iraki, Peter Fitschen, Sergio Espinar, and Eric Helms, “Nutrition Recommendations for Bodybuilders in the Off - Season: A Narrative Review.” Sports (Basel, Switzerland.), Vol. 7.7 154, 26 Jun 2019.

8. Burd NA, Tang JE, Moore DR, Phillips SM. “Exercise training and protein metabolism: influences of contraction, protein intake, and sex - based differences.” J Appl Physiol (1985). 2009 May;106(5):1692 - 701.

9. Schoenfeld, B.J., Aragon, A.A. “How much protein can the body use in a single meal for muscle - building? Implications for daily protein distribution.” J Int Soc Sports Nutr 15, 10 (2018).

10. Kerksick CM, Arent S, Schoenfeld BJ, Stout JR, Campbell B, Wilborn CD, Taylor L, Kalman D, Smith - Ryan AE, Kreider RB, Willoughby D, Arciero PJ, VanDusseldorp TA, Ormsbee MJ, Wildman R, Greenwood M, Ziegenfuss TN, Aragon AA, Antonio J. “International society of sports nutrition position stand: nutrient timing.” J Int Soc Sports Nutr. 2017 Aug 29;14:33.