Fructose and glucose co-ingestion during prolonged exercise increases lactate and glucose fluxes and oxidation compared with an equimolar intake of glucose

Background When fructose is ingested together with glucose (GLUFRU) during exercise plasma lactate and exogenous carbo hydrate oxidation rates me higher than with glucose done Objective The objective was to investigate to what extent GLUFRU increased lactate kinetics and oxidation rate and gluconeogenesis from lactate (GNG(L)) and from fructose (GNG(F)) Design Seven endurance trained men performed 120 min of exercise at approximate to 60% VO(2)max (maximal oxygen consumption) while in gesting 1 2 g glucose/min + 0 8 g of either glucose or fructose/min (GLUFRU) In 2 trials the effects of glucose and GLUFRU on lactate and glucose kinetics were investigated with glucose and lactate tracers In a third trial labeled fructose was added to GLUFRU to assess fructose disposal Results In GLUFRU lactate appearance (120 +/- 6 mu mol kg(-1) min(-1)) lactate disappearance (121 +/- 7 mu mol kg(-1) min(-1)) and oxidation (127 +/- 12 mu mol kg(-1) min(-1)) rates increased significantly (P < 0 001) in comparison with glucose alone (94 +/- 16 95 +/- 16 and 97 +/- 16 mu mol kg(-1) min(-1) respectively) GNG(I) was negligible in both conditions In GLUFRU GNG(F) and exogenous fructose oxidation increased with time and leveled oil at 18 8 +/- 3 7 and 38 +/- 4 mu mol kg(-1) min(-1) respectively at 100 mm Plasma glucose appearance rate was significantly higher (P < 0 01) in GLUFRU (91 +/- 6 mu mol kg(-1)) than in glucose done (82 +/- 9 mu mol kg(-1) min(-1)) Carbohydrate oxidation rate was higher (P < 0 05) in GLUFRU Conclusions Fructose increased total carbohydrate ate oxidation lactate production and oxidation and GNG(F) Fructose oxidation was explained equally by fructose-derived lactate and glucose oxidation most likely in skeletal and cardiac muscle This trial was registered at clinicaltrials gov as NCT01128647 Am J Clin Nutr 2010 92 1071-9