Fructose-Glucose Composite Carbohydrates and Endurance Performance: Critical Review and Future Perspectives.

Sports beverages formulated with fructose and glucose composites enhance exogenous carbohydrate oxidation, gut comfort, and endurance performance, relative to single-saccharide formulations. However, a critical review of performance data is absent. We conducted a comprehensive literature review of the effect of fructose:glucose/maltodextrin (glucose or maltodextrin) composites versus glucose/maltodextrin on endurance performance. Mechanistic associations were drawn from effects on carbohydrate metabolism, gut, and other sensory responses. Overall, 14 studies contained estimates of 2.5-3.0-h endurance performance in men, mostly in cycling. Relative to isocaloric glucose/maltodextrin, the ingestion of 0.5-1.0:1-ratio fructose:glucose/maltodextrin beverages at 1.3-2.4 g carbohydrate·min(-1) produced small to moderate enhancements (1-9 %; 95 % confidence interval 0-19) in mean power. When 0.5:1-ratio composites were ingested at ≥1.7 g·min(-1), improvements were larger (4-9 %; 2-19) than at 1.4-1.6 g·min(-1) (1-3 %; 0-6). The effect sizes at higher ingestion rates were associated with increased exogenous carbohydrate oxidation rate, unilateral fluid absorption, and lower gastrointestinal distress, relative to control. Solutions containing a 0.7-1.0:1 fructose:glucose ratio were absorbed fastest; when ingested at 1.5-1.8 g·min(-1), a 0.8:1 fructose:glucose ratio conveyed the highest exogenous carbohydrate energy and endurance power compared with lower or higher fructose:glucose ratios. To conclude, ingesting 0.5-1.0:1-ratio fructose:glucose/maltodextrin beverages at 1.3-2.4 g·min(-1) likely benefits 2.5-3.0 h endurance power versus isocaloric single saccharide. Further ratio and dose-response research should determine if meaningful performance benefits of composites accrue with ingestion <1.3 g·min(-1), relative to higher doses. Effects should be established in competition, females, other food formats, and in heat-stress and ultra-endurance exercise where carbohydrate demands may differ from the current analysis.