Roberts, J. D., Tarpey, M. D., Kass, L., Tarpey, R. J., & Roberts, M. G. (2010). The influence of fructose ingestion on exogenous carbohydrate oxidation, fluid availability and exercise performance. Presentation 857 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

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There is increasing scientific interest in the use of combined carbohydrate beverages to enhance exogenous carbohydrate oxidation (CHOexo) rates for endurance athletes. This study ascertained CHOexo rates, fluid availability, and performance times of a maltodextrin/fructose beverage in comparison to an isoenergetic maltodextrin beverage and a placebo. Trained cyclists/triathletes (N = 14) performed three exercise trials on a cycle-ergometer. Each trial involved 2.5 hours steady state exercise at 50% maximum power output followed by a 60 km time-trial performance test. Athletes were randomly assigned one of three drinks in a double-blind manner throughout each trial: (1) 1.1 g/minute maltodextrin + 0.6 g/minute fructose, (2) 1.7 g/minute of maltodextrin, or (3) aspartame sweetened flavored water as a placebo. In addition, for seven subjects, the test beverage at 60 minutes into each oxidation trial contained 5.0 g of deuterium oxide (2H2O) to assess fluid availability. Expired air samples were later analyzed for CHOexo.

Peak CHOexo was significantly greater with maltodextrin+fructose and maltodextrin-alone conditions compared to the placebo. Additionally, peak CHOexo was significantly greater with maltodextrin+fructose compared to maltodextrin-alone. The overall appearance of 2H2O in the plasma was significantly greater in both the placebo and maltodextrin+fructose compared to the maltodextrin-alone condition. There was no significant difference in fluid availability between the placebo and maltodextrin+fructose conditions. No significant differences were found between groups for the performance tests.

Implication. The addition of fructose to a maltodextrin beverage improves average and peak CHOexo and fluid availability.

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