title: Oxidation of combined ingestion of glucose and fructose during exercise.
abstract: The purpose of the present study was to examine whether combined ingestion of a large amount of fructose and glucose during cycling exercise would lead to exogenous carbohydrate oxidation rates >1 g/min. Eight trained cyclists (maximal O(2) consumption: 62 +/- 3 ml x kg(-1) x min(-1)) performed four exercise trials in random order. Each trial consisted of 120 min of cycling at 50% maximum power output (63 +/- 2% maximal O(2) consumption), while subjects received a solution providing either 1.2 g/min of glucose (Med-Glu), 1.8 g/min of glucose (High-Glu), 0.6 g/min of fructose + 1.2 g/min of glucose (Fruc+Glu), or water. The ingested fructose was labeled with [U-(13)C]fructose, and the ingested glucose was labeled with [U-(14)C]glucose. Peak exogenous carbohydrate oxidation rates were approximately 55% higher (P < 0.001) in Fruc+Glu (1.26 +/- 0.07 g/min) compared with Med-Glu and High-Glu (0.80 +/- 0.04 and 0.83 +/- 0.05 g/min, respectively). Furthermore, the average exogenous carbohydrate oxidation rates over the 60- to 120-min exercise period were higher (P < 0.001) in Fruc+Glu compared with Med-Glu and High-Glu (1.16 +/- 0.06, 0.75 +/- 0.04, and 0.75 +/- 0.04 g/min, respectively). There was a trend toward a lower endogenous carbohydrate oxidation in Fruc+Glu compared with the other two carbohydrate trials, but this failed to reach statistical significance (P = 0.075). The present results demonstrate that, when fructose and glucose are ingested simultaneously at high rates during cycling exercise, exogenous carbohydrate oxidation rates can reach peak values of approximately 1.3 g/min.
authors.affiliation: Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, B15 2TT, Birmingham, UK.
authors.forename: Roy L P G
authors.initials: RL
authors.lastname: Jentjens
authors.forename: Luke
authors.initials: L
authors.lastname: Moseley
authors.forename: Rosemary H
authors.initials: RH
authors.lastname: Waring
authors.forename: Leslie K
authors.initials: LK
authors.lastname: Harding
authors.forename: Asker E
authors.initials: AE
authors.lastname: Jeukendrup
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D004040:Dietary Carbohydrates / Q000378:metabolism; D004338:Drug Combinations; D015444:Exercise / Q000502:physiology*; D005223:Fats / Q000378:metabolism; D005632:Fructose / Q000008:administration & dosage* / Q000378:metabolism*; D005767:Gastrointestinal Diseases / Q000453:epidemiology; D005947:Glucose / Q000008:administration & dosage* / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D007773:Lactates / Q000097:blood; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D004040:Dietary Carbohydrates; D004338:Drug Combinations; D005223:Fats; D007773:Lactates; D005632:Fructose; D005947:Glucose