Oral Rehydration Beverages for Treating Exercise-Associated Dehydration: A Systematic Review, Part II. The Effectiveness of Alternatives to Carbohydrate-Electrolyte Drinks.

Objective: Dehydration associated with exertion is a commonly encountered condition in the first aid setting, particularly at outdoor sporting events. Part I of this systematic review demonstrated that commercial sports drinks can be suggested for effective restoration of fluid balance in dehydrated people. In part II, we perform a systematic review to compare alternative liquids, such as cow's milk, beer, and coconut water, with water for effective oral rehydration after prolonged exercise.

Data sources: Cochrane Library, MEDLINE via the PubMed interface, and Embase databases were searched up until June 1, 2022.

Study selection: Controlled experimental and observational studies involving adults and children were included when dehydration was induced by physical exercise and oral rehydration fluids were administered and compared with regular water. No additional food intake accompanied the rehydration drinks or water. Articles in all languages were included if an English abstract was available.

Data extraction: Study design, study population, intervention, outcome measures, and study limitations were extracted from each included article.

Data synthesis: Of 3485 articles screened, 11 articles in which authors compared skim or low-fat cow's milk, coconut water, or beer (0%-5% alcohol) with water were included. Authors of 4 studies showed that drinking skim or low-fat milk, without additional food intake, led to improved volume/hydration status compared with drinking water. Authors of 3 trials showed no differences at multiple times for outcomes related to volume/hydration status after rehydration with fresh coconut water compared with water. Evidence to recommend beer (0%-5% alcohol) for rehydration is insufficient.

Conclusions: Consuming skim or low-fat cow's milk without additional food intake as compared with water appears to improve volume/hydration status in people with exercise-induced dehydration. However, evidence is of very low certainty and should be interpreted with caution.