Fructose and Sucrose Intake Increase Exogenous Carbohydrate Oxidation during Exercise

Peak exogenous carbohydrate oxidation rates typically reach ~1 g·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·kg(−1)·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·min(−1) of glucose (GLU), 1.2 g·min(−1) glucose + 0.6 g·min(−1) fructose (GLU + FRU), 0.6 g·min(−1) glucose + 1.2 g·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·min(−1), respectively, p = 0.999), but were 46% ± 8% higher when compared to GLU (0.96 ± 0.06 g·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·min(−1), respectively, p < 0.05). We conclude that fructose co-ingestion (0.6 g·min(−1)) with glucose (1.2 g·min(−1)) provided either as a monosaccharide or as sucrose strongly increases exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists.