These receptors are independent of ordinary taste buds, says Ed Chambers, PhD, of the University of Birmingham in England and lead author of the study.
Chambers tells WebMD by email that the "study suggests that the human mouth may have receptors sensitive to carbohydrate that are independent of the 'sweet' taste receptor. This supports research performed with rodents that suggests these mammals have taste receptors that are responsive to carbohydrate."
His research team mixed pseudo-sports drinks that contained either carbohydrates (glucose or maltodextrin) or a third concoction of water laced with artificial sweeteners.
Then eight endurance-trained cyclists were asked to complete a challenging workout, during which they swished with one of the three liquids for 10 seconds, spitting the drink out and not swallowing.
Those athletes who used the glucose or maltodextrin drinks to rinse their mouths did 2% to 3% better than exercisers who swished the artificially sweetened water, the “placebo” sports drink, the researchers say.
And, they found that the glucose and maltodextrin triggered specific areas of the brain that are associated with pleasure or reward, but the artificially sweetened water did not.
"Our results suggest that any carbohydrate in the mouth could improve exercise performance," he tells WebMD. "However, this has only been demonstrated with glucose and maltodextrin and would need to be proven. We want to make clear that the study does not imply that athletes do not need to swallow energy drinks during exercise. The research has identified that as well as the well-known metabolic benefits of ingesting carbohydrate drinks during exercise there is a direct 'central' benefit from simply tasting these substances," Chambers tells WebMD in an email.