Protein with Carbohydrate for Post-Exercise Glycogen Recovery?

Recovery after training is a fundamental process in performance improvement. Specifically, the restoration of muscle glycogen stores (which decrease during exercise, especially if performed at high intensity) should be a main goal in recovery, since low glycogen stores can affect performance in subsequent training sessions.

Carbohydrates are the main source of energy to restore glycogen stores. In fact, current guidelines recommend consuming 1,2 grams of carbohydrates per kilogram of body weight each hour during the 4-6 hours after exercise.1 In this regard, it has traditionally been proposed that, since proteins can increase the insulin response, that increase in insulin levels could facilitate the entry of carbohydrates into the muscle and thus facilitate glycogen synthesis.2 Therefore, protein intake could not only facilitate the recovery of muscle tissue thanks to the stimulation of protein synthesis, but also the recovery of glycogen stores. Taking this evidence into account, it might be convenient to add proteins to carbohydrates after exercise sessions if the goal is to maximize glycogen synthesis to perform in subsequent sessions, but what does science say? 

Trying to answer this question, a meta-analysis included 20 studies that compared the effects of taking only carbohydrates or carbohydrates together with proteins on post-exercise muscle glycogen synthesis.3 The results show that, when the same amount of energy is ingested, glycogen synthesis is the same whether proteins are consumed or not along with carbohydrates. However, when the addition of proteins implies a higher calorie intake, glycogen synthesis is increased.3

On the other hand, if we consider the effects on sports performance in subsequent sessions, a recent meta-analysis that included 30 studies concluded that the combination of proteins and carbohydrates after an exercise session improves performance in subsequent physical tests (time trial or exhaustion test) compared to taking only carbohydrates, especially when the recovery time was more than 8 hours.4 However, the benefits disappeared when the supplements were isocaloric, that is, when the same energy was provided by taking only carbohydrates or combining them with protein.4 These results suggest that the benefits of adding protein could be due to a higher caloric intake, since when carbohydrates are replaced by protein (rather than adding protein to a certain amount of carbohydrates), no benefits are obtained.

Conclusions

Carbohydrates continue to be shown as the main nutrient to facilitate post-exercise glycogen recovery and to perform in a subsequent session, something of special relevance especially in athletes who double training sessions (that is, multiple sessions in a day). These meta-analyses show that, when proteins are added to a certain amount of carbohydrates (therefore consuming more calories), glycogen synthesis will be accelerated and physical performance in subsequent sessions will improve.However, the benefits are not so clear when part of the carbohydrates is replaced (instead of added) with proteins. In this case, and given that studies do not show benefits but nor do they show harm, it has been suggested that it may be advisable to slightly reduce the amount of carbohydrates consumed after exercise (0.9 g/kg/hour) but increase protein intake (0.3 g/kg/hour) to obtain benefits not only in glycogen synthesis but also in muscle tissue recovery.3

AUTHOR

Pedro Valenzuela
Researcher in the Physiology Unit of the University of Alcalá and in the Performance Control Unit at the Center for Sports Medicine (AEPSAD, CAR of Madrid).
Web: www.fissac.com

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References

1. Thomas D, Erdman K, Burke L. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852
2. Doi M, Yamaoka I, Nakayama M, Mochizuki S, Sugahara K, Yoshizawa F. Isoleucine, a blood glucose-lowering amino acid, increases glucose uptake in rat skeletal muscle in the absence of increases in AMP-activated protein activity. J Nutr. 2005;135(9):2103-2108. doi:10.1093/jn/135.9.2103
3. Margolis LM, Allen JT, Hatch-McChesney A, Pasiakos SM. Coingestion of Carbohydrate and Protein on Muscle Glycogen Synthesis after Exercise. Med Sci Sport Exerc. 2020;Publish Ahead of Print(8):384-393. doi:10.1249/mss.0000000000002476

4. Nielsen LLK, Lambert MNT, Jeppesen PB. The effect of ingesting carbohydrate and proteins on athletic performance: A systematic review and meta-analysis of randomized controlled trials. Nutrients. 2020;12(5). doi:10.3390/nu12051483