Written by: Tim Mickleborough, PhD
Dear Speed Lab,
Do you know if a change in sports drink flavor during exercise can affect exercise performance? I know that Speed Lab has previously discussed the influence of carbohydrate mouth rinses on performance, but I wonder whether much has been done on the flavor of a drink.
Chapel Hill, N.C.
Studies have investigated the effects of drink flavor on ad libitum (i.e. voluntary) fluid consumption during exercise in order to minimize the effects of dehydration. Wilk, et al., observed that boys voluntarily drank significantly more grape-flavored water than plain water in the heat and consequently became less dehydrated with the flavored option.1 Interestingly, however, subjects drank even more and prevented dehydration altogether when provided a grape-flavored beverage that also contained carbohydrate. It appears, then, that flavor is not the only factor that affects voluntary drinking rates during exercise.
A more recent study by Chambers, et al., provides indirect evidence that the presence of carbohydrate in a sports drink may increase voluntary drinking rates by activating a reward center in the brain.2 However, this study did not involve actual sports drink consumption, but was a follow-up study to the carbohydrate mouth rinse study you referenced in your question. This study investigated how rinsing the mouth with solutions containing glucose and maltodextrin, disguised with artificial sweetener, would affect exercise performance. The second aim was to use functional magnetic resonance imaging to identify the brain regions activated by these substances.
The cyclists completed a cycle time trial significantly faster when rinsing their mouths with a 6.4 percent glucose solution compared with a placebo containing saccharin. The corresponding fMRI study revealed that oral exposure to glucose activated reward-related brain regions, including the anterior cingulate cortex and striatum, which were unresponsive to saccharin. Finally, the endurance-trained cyclists tested the effect of rinsing with a 6.4 percent maltodextrin solution on exercise performance, showing it to significantly reduce the time to complete the cycle time trial compared to an artificially sweetened placebo. The authors concluded that there may be a class of currently unidentified oral receptors that respond to CHO independently of those for sweetness.
Only two studies have directly investigated the effect of a drink-flavor change on exercise performance when beverage volume and CHO content were controlled. Carter, et al.,4 showed that drink sweetness did not affect endurance cycling performance compared with an unsweetened but CHO-matched control drink. However, the different beverage flavors were provided to the athletes at the beginning of each exercise session rather than as a flavor change during exercise. Subsequently, Desbrow, et al.,5 investigated whether changing flavor of a beverage administered during endurance cycling would improve exercise performance. They found that changing drink flavor caused no change in heart rate, blood glucose, ratings of perceived exertion or cycling performance.
There is one other study that may have relevance to your question. Cox and colleagues showed that time-trial performance improved when switching from a CHO-containing sports drink to Coca-Cola during the latter stages of a 2.5-hour cycling bout. While the authors attributed the performance increase to the ergogenic effects of caffeine and glucose, it is possible that drink flavor may in part be responsible for the performance improvement.
1. Wilk B, Bar-Or O. Effect of drink flavor and NaCL on voluntary drinking and hydration in boys exercising in the heat. J Appl Physiol. 1996 Apr;80(4):1112-7
2 Chamber, E.S., M.W. Bridge and D.A. Jones. “Carbohydrate sensing in the human mouth: effects on exercise performance and brain activity.” The Journal of Physiology. 587 (2009): 1779-1794.
3. Cox, G., B. Desbrow, P. Montgomery et al. “Effect of different protocols of caffeine intake on metabolism and endurance performance.” Journal of Applied Physiology. 93 (2002): 990-999.
4. Carter, J., A. Jeukendrup and D. Jones. “The effect of sweetness on the efficacy of carbohydrate supplementation during exercise in the heat.” Canadian Journal of Applied Physiology. 30 (2005): 379-391.
5. Desbrow, B., C. Minahan and M. Leveritt. “Drink-flavor change’s lack of effect on endurance cycling performance in trained athletes.” International Journal of Sport Nutrition and Exercise Metabolism. 17 (2007): 315-327.