• Why Do Sports Drinks Work?

    Dr. Noakes has shown that there is no compelling evidence that athletes competing in endurance events (at least up to marathon distances) benefit from sports drinks because they contain water and/or electrolytes. However,there is convincing research proving that the consumption of carbohydrate-containing drinks during athletic events lasting an hour or longer does enhance performance (1, 2). However, it now appears the enhanced performance shown in studies where subjects consumed sports drinks comes largely from the ingestion of the carbohydrate rather than from the water or electrolytes they contain. Most data suggests that in prolonged endurance events the consumption of between 40 and 80g of carbohydrate per hour will maximally improve performance, perhaps by maintaining blood sugar levels and reducing mental fatigue and/or by slowing the breakdown of glycogen reserves. As more athletes become aware of the need to avoid consuming too much fluid during exercise, many have turned to commercial products that contain carbohydrate such as sports, gels, chews, and “beans.”

    While commercial carbohydrate-rich products allow people to better control their carbohydrate intake independently of fluid intake, these products are mostly just refined sugars, so an important question is would a whole food (like fruit) work just as well. To answer this question, Dr. Casazza at UC Davis examined the impact of consuming either raisins or a commercial sports product or water only in a group of eleven very fit young men. All subjects consumed the same amount of water by drinking about 500 ml per hour while exercising. All subjects exercised in the lab for 80 minutes at a fairly intense pace (75% VO2max) and then immediately performed a timed 5K run as fast as possible. When the subjects consumed only water, it took them an average of 21.6 minutes to run the 5K. However, after consuming the raisins and commercial chews the running times dropped significantly to 20.6 minutes with the raisins and 20.7 minutes with the sports chews.The authors concluded: “Raisins and chews promoted higher carbohydrate oxidation and improved running performance compared to water only. Running performance was similar between the raisins and chews, with no significant GI differences” (3).

    Bottom Line: Commercial supplemental carbohydrate products and sports drinks offer no proven performance enhancement compared to plain water and whole fruit. However, these commercial sports nutrition products generally contain more added salt and fewer nutrients than simply consuming fruit when one needs a boost from extra carbohydrate and drinking water when thirsty.

    By James J. Kenney, PhD FACN

    1. Coogan AR, Coyle EF. Reversal of fatigue during prolonged exercise by carbohydrate infusion or ingestion. J Appl Physiol 1987; 63: 2388-95.
    2. Jeukendrup AE. Carbohydrate intake during exercise and performance. Nutrition 2004; 20: 669-77.
    3. Too BW, et al. Natural versus commercial carbohydrate supplementation and endurance running performance. J Inter Soc Sports Nutr 2012; 9: 27-34.
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