Hyperhydrating with glycerol: Implications for athletic performance

Small decreases in hydration status can result in a dramatic decrement in a thletic performance and greatly increase the risk of thermal injury. Becaus e of its osmotic properties, which enable greater fluid retention than the ingestion of water alone, glycerol has been proposed as a hyperhydrating ag ent. In fact, glycerol is now commercially available and marketed as a spor t supplement to be ingested with water or sport drinks; thus, dietitians ne ed to be cognizant of this new addition to the sports nutrition table. The results of glycerol-induced hyperhydration research have been equivocal, mo st likely because of methodologic differences between studies, such as vari ations in the intensity of exercise, environmental conditions, and concentr ation or dose of glycerol administered. Although the suggested dosage of gl ycerol depends on body size and varies between manufacturers, 1 g/kg body w eight with an additional 1.5 L fluid taken 60 to 120 minutes before competi tion is standard. Some test subjects reported feeling bloated or nauseated after ingesting glycerol. This review examines glycerol-induced hyperhydrat ion research and the safety of ingesting glycerol, discusses commercial ava ilability of glycerol, and makes recommendations for glycerol-induced hyper hydration research.