Fructose and Sucrose Intake Increase Exogenous Carbohydrate Oxidation during Exercise

Peak exogenous carbohydrate oxidation rates typically reach 1 g center dot min(-1) during exercise when ample glucose or glucose polymers are ingested. Fructose co-ingestion has been shown to further increase exogenous carbohydrate oxidation rates. The purpose of this study was to assess the impact of fructose co-ingestion provided either as a monosaccharide or as part of the disaccharide sucrose on exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists. Ten trained male cyclists (VO(2)peak: 65 +/- 2 mL center dot kg(-1)center dot min(-1)) cycled on four different occasions for 180 min at 50% W-max during which they consumed a carbohydrate solution providing 1.8 g center dot min(-1) of glucose (GLU), 1.2 g center dot min(-1) glucose + 0.6 g center dot min(-1) fructose (GLU + FRU), 0.6 g center dot min(-1) glucose + 1.2 g center dot min(-1) sucrose (GLU + SUC), or water (WAT). Peak exogenous carbohydrate oxidation rates did not differ between GLU + FRU and GLU + SUC (1.40 +/- 0.06 vs. 1.29 +/- 0.07 g center dot min(-1), respectively, p = 0.999), but were 46% +/- 8% higher when compared to GLU (0.96 +/- 0.06 g center dot min(-1): p < 0.05). In line, exogenous carbohydrate oxidation rates during the latter 120 min of exercise were 46% +/- 8% higher in GLU + FRU or GLU + SUC compared with GLU (1.19 +/- 0.12, 1.13 +/- 0.21, and 0.82 +/- 0.16 g center dot min(-1), respectively, p < 0.05). We conclude that fructose co-ingestion (0.6 g center dot min(-1)) with glucose (1.2 g center dot min(-1)) provided either as a monosaccharide or as sucrose strongly increases exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists.