A recent review article by Trommelen et al tackled the age old question with a comprehensive analysis of over one hundred sports medicine-related research papers. Our bodies are highly adaptive and are constantly varying the rates of muscle turnover and breakdown based on our nutritional status and activity level. Finding a balance between protein synthesis and breakdown is important in maintaining lean mass and a healthy bodyweight. A single exercise session can stimulate muscle protein synthesis, however without food, our bodies’ protein balance will remain negative, lending to more breakdown. Protein ingestion promotes more muscle protein synthesis (MPS) and inhibits breakdown after exercise.
There are many factors affecting how ingested protein affects our rates of muscle protein synthesis, including the timing, the amount, and the type of protein. Many previous papers have shown that isolated amino acids and quickly digestible proteins aid in muscle synthesis, however few have examined how a traditional mixed meal affects muscle synthesis. Additional variables affecting synthesis rates include diet (outside of the post-exercise window), alcohol use, body composition, age, and/or sex. And while many factors have been studied, several more are needed to address unanswered questions regarding long-term factors and newer supplements.
As far as the amount of protein needed after exercise, several studies have shown that 20g of protein produced the greatest increase in muscle protein synthesis, although a very modest increase was noted with 40g of protein as well. These studies also incorporated a standardized meal of 20g of whey protein four hours before exercise to maximize muscle protein synthesis rates. To maximize prolonged rates of muscle protein synthesis, it has also been shown that 40g of slowly digestible protein, such as casein, can be supplemented prior to sleep or when feeding may be postponed for more than 6 hours.
In addition to the amount of protein ingested, the type of protein also impacts how much muscle synthesis can occur after exercise. Animal-based proteins, such as whey or egg, have greater muscle protein synthesis rates than that of plant-based proteins, which may be partly due to a more complete amino acid profile of animal proteins and digestibility. However, it has been shown that comparable muscle protein synthesis rates may occur with greater amounts of plant-based protein. This is not to discourage avoidance of plant-based proteins, as many mixed meals contain enough protein sources to make a balanced amino acid profile.
While there are many factors that contribute to muscle protein synthesis, it is important to realize that all of the components can be tailored to the individual based on his/her nutritional and performance-related goals. For personalized nutrition and exercise support contact Scottsdale Sport Medicine Institute!
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Dr, Carfagno, D.O. C.A.Q.S.M. is board certified in Sports and Internal Medicine, two doctors in one.
He founded SSMI sixteen years ago with the philosophy of “Treating YOU Like Family”.
His innovative approach to care has made him a healthcare leader locally and internationally. He is a graduate of the world-renowned Cleveland Clinic.
Trommelen, J., Betz, M.W. & van Loon, L.J.C. The Muscle Protein Synthetic Response to Meal Ingestion Following Resistance-Type Exercise. Sports Med (2019) 49: 185. https://doi.org/10.1007/s40279-019-01053-5