Several sports drinks have began to add protein to carbohydrate based on research showing a positive effect on exercise tolerance. Can adding protein to carbohydrate during exercise have a positive effect on performance? My colleagues at the University of Connecticut addressed this question in a recently published meta-analysis by and they asked me to be a co-author on the paper. We examined a total of 11 studies that tested the effects of protein added to carbohydrates during exercise on performance. Carbohydrate alone was the control and the effects of adding protein (usually whey protein) to the carbohydrate on performance was assessed by either time trial or time to exhaustion test. The primary finding was that co-ingestion of protein with carbohydrate during exercise improved exercise performance by an average of 9% compared to carbohydrate alone. Several possible reasons may explain why adding protein to carbs enhances performance. Prolonged endurance exercise can result in significant protein breakdown to provide fuel for exercise, which may be offset by adding protein. Protein may aid recovery from exercise by providing amino acid building blocks for protein synthesis that would otherwise need to be broken down from existing muscle. This is turn would require an increase in cortisol. Thus protein could prevent a catabolic state. Certain amino acids may also enhance exercise-related immune responses. Regardless of the exact mechanisms, the preponderance of evidence indicates that adding protein to carbohydrate helps endurance athletes, even when additional carbohydrate is added to match for total calories. Strength athletes are not the only ones who benefit from including protein in their sports beverage.
. Stearns RL, Emmanuel H, Volek JS, Casa DJ. Effects of ingesting protein in combination with carbohydrate during exercise on endurance performance: a systematic review with meta-analysis. J Strength Cond Res. 2010 Aug;24(8):2192-202.