Carb Drinks Rehydrate Better than Water
If you are going out for a long bike ride or a run and have a water bottle, it’s best to fill it with carbs if your looking to properly rehydrate your fluids. Proper fluid replacement before, during, and after exercise can positively influence how you feel and how you perform. Most people do not realize how quickly water can be lost from our bodies when exercising. The heat production rate in active, exercising muscles can be 100 times that of resting muscles. Rehydration will occur more rapidly when beverages containing sodium (the major electrolyte lost in sweat), are consumed. Ingesting a beverage containing sodium allows the plasma sodium to remain elevated during the rehydration period and helps maintain thirst while delaying stimulation of urine production. The rehydration beverage should also contain glucose or sucrose because these carbohydrates provide a source of energy for working muscles, stimulate fluid absorption in the gut, and improve beverage taste.
Researchers examined how carbohydrate content of drinks on their rehydration effectiveness after exercise-induced dehydration. Six healthy male volunteers were dehydrated by 1.9+/-0.1% of body mass by intermittent cycle ergometer exercise in the heat before ingesting one of three solutions with different carbohydrate contents and osmolalities over a period of 1-hour. Thirty minutes after the cessation of exercise, subjects drank a volume that amounted to 150% of their body mass loss. One session they drank a drink that contained no glucose, the next session a drink containing 2 percent glucose, and the third session a drink containing 10 percent glucose. All drinks contained 25 mmole of sodium. At the end of the study, significantly more of the ingested fluid was retained in the 10% glucose trial than in the 0% trial. Subjects remained euhydrated for 1- hour longer in the 10% glucose trial than in the 2% glucose trial. In the 2% glucose trial, plasma volume was elevated immediately after and 1-hour after rehydration. This study suggests that, following the rehydration protocol used, hypertonic glucose-sodium drinks may be more effective at restoring and maintaining hydration status after sweat loss than more dilute solutions when the sodium concentration is comparable.
Evans GH, Shirreffs SM, Maughan RJ. Postexercise rehydration in man: the effects of osmolality and carbohydrate content of ingested drinks. Nutrition. 2009 Sep;25(9):905-13.