Restoration of energy stores and recovery of muscle damage are key factors determining the performance in endurance events. Therefore, nutrition aimed to fasten and help in these processes has received a lot of attention lately and is the focus of a recent meta-analysis comparing the effects of carbohydrates CHO and carbohydrates+proteins CHO+PRO ingestion on athletic performance.
Carbohydrates are stored as glycogen in the liver and muscles and is a major energy source during long moderate/high intensity exercise. Low muscle glycogen concentration leads to fatigue.
Restoration of glycogen levels usually takes 24 hours, if there is enough supply of carbohydrates. For short-term recovery (less than 8h) is recommended to consume 1.2-1.5g of carbohydrates per kilogram of weight and hour. Moreover, it has been suggested to start taking carbohydrates immediately, within 30 minutes of finishing the effort, and at frequent intervals onwards. Doing it so keeps high the levels of glucose and insulin in plasma, maximizing muscle glycogen synthesis.
For athletes participating in endurance events lasting more than 1h, carbohydrates are recommended at levels of 30-60g/h and intervals of 15-20 minutes.
Regarding the simultaneous consumption of carbohydrates and proteins the articles found differed greatly in many aspects such as: protocol design, duration of recovery, preceding exercise to deplete the muscle glycogen levels, or exercise type, among others. Additionally, many studies used Time-To-Exhaustion or TTE, while others used Time-Trial performance, or TT, a test usually considered more physiological and reliable.
Co-ingestion of carbohydrates and proteins (CHO+PRO), significantly improved athletic performance when compared with carbohydrates (CHO) alone. TTE was 2.2 minutes longer in the athletes that used CHO+PRO. Thus, there is an ergogenic effect of CHO+PRO, with performance benefits present when protein is added to an optimal amount of CHO.
And this improvement in performance by combining the ingestion of both substances was only evident during long-term recovery periods, longer than 8h. On the contrary, no significant effects were found using both substances when the recovery period was shorter than 8h.
- IF you have more than 8h recovery time: combine CHO+PRO ingestion, during and/or following an exercise bout.
- IF you have less than 8h recovery time: there is no difference between using CHO and CHO+PRO, but you should ensure to replenish adequately glycogen deposits.
The Effect of Ingesting Carbohydrate and Proteins on Athletic Performance: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Kloby Nielsen LL, Tandrup Lambert MN, Jeppesen PB. Nutrients. 2020;12(5):1483. Published 2020 May 20. doi:10.3390/nu12051483