Typically, athletes consume water and carbohydrates to rehydrate after exercise. Researchers in the United Kingdom speculated that adding protein might help. They asked healthy men to participate in two exercise trials in the heat until the men lost 2% of their body weight.
During the first hour of post-exercise recovery, the participants were provided fluid that contained either 65g of carbs or 40g carbs with 25g of milk protein.
With the carb-only group, urine output was slightly greater over a four-hour recovery period. For the carb plus protein group, whole body net fluid balance was significantly greater at the 3 and 4 hour marks during the exercise recovery period.
Thus, adding protein to a carbohydrate beverage during recovery improves rehydration in addition to other established benefits, such as promoting a more anabolic environment for recovery.