Oxidation of combined ingestion of glucose and fructose during exercise (original) (raw)
American Journal of Clinical Nutrition, 2010
Background: When fructose is ingested together with glucose (GLUFRU) during exercise, plasma lactate and exogenous carbohydrate oxidation rates are higher than with glucose alone. 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 '60% _ VO 2 max (maximal oxygen consumption) while ingesting 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 6 lmol Á kg 21 Á min 21 ), lactate disappearance (121 6 7 lmol Á kg 21 Á min 21 ), and oxidation (127 6 12 lmol Á kg 21 Á min 21 ) rates increased significantly (P , 0.001) in comparison with glucose alone (94 6 16, 95 6 16, and 97 6 16 lmol Á kg 21 Á min 21 , respectively). GNG L was negligible in both conditions. In GLUFRU, GNG F and exogenous fructose oxidation increased with time and leveled off at 18.8 6 3.7 and 38 6 4 lmol Á kg 21 Á min 21 , respectively, at 100 min. Plasma glucose appearance rate was significantly higher (P , 0.01) in GLUFRU (91 6 6 lmol Á kg 21 Á min 21 ) than in glucose alone (82 6 9 lmol Á kg 21 Á min 21 ). Carbohydrate oxidation rate was higher (P , 0.05) in GLUFRU. Conclusions: Fructose increased total carbohydrate 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.
Respective oxidation of 13C-labeled lactate and glucose ingested simultaneously during exercise
Journal of applied physiology (Bethesda, Md. : 1985), 1997
The purpose of this experiment was to measure, by using 13C labeling, the oxidation rate of exogenous lactate (25 g, as Na+, K+, Ca2+, and Mg2+ salts) and glucose (75 g) ingested simultaneously (in 1,000 ml of water) during prolonged exercise (120 min, 65 +/- 3% maximum oxygen uptake in 6 male subjects). The percentage of exogenous glucose and lactate oxidized were similar (48 +/-3 vs. 45 +/- 5%, respectively). However, because of the small amount of oral lactate that could be tolerated without gastrointestinal discomfort, the amount of exogenous lactate oxidized was much smaller than that of exogenous glucose (11.1 +/- 0.5 vs. 36.3 +/- 1.3 g, respectively) and contributed to only 2.6 +/- 0.4% of the energy yield (vs. 8.4 +/- 1.9% for exogenous glucose). The cumulative amount of exogenous glucose and lactate oxidized was similar to that observed when 100 g of [13C]glucose were ingested (47.3 +/- 1.8 vs. 50.9 +/- 1.2 g, respectively). When [13C]glucose was ingested, changes in the pl...
Physiological reports, 2017
This study compared the effects of coingesting glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at altitude and sea level, in men. Seven male British military personnel completed two bouts of cycling at the same relative workload (55% Wmax) for 120 min on acute exposure to altitude (3375 m) and at sea level (~113 m). In each trial, participants ingested 1.2 g·min(-1) of glucose (enriched with (13)C glucose) and 0.6 g·min(-1) of fructose (enriched with (13)C fructose) directly before and every 15 min during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation, and endogenous glucose oxidation derived from liver and muscle glycogen. Total carbohydrate oxidation during the exercise period was lower at altitude (157.7 ± 56.3 g) than sea level (286.5 ± 56.2 g, P = 0.006, ES = 2.28), whereas fat oxidation was higher at altit...
European Journal of Applied Physiology
Purpose This study aimed to investigate whether carbohydrate ingestion during 3 h long endurance exercise in highly trained cyclists at a rate of 120 g h−1 in 0.8:1 ratio between fructose and glucose-based carbohydrates would result in higher exogenous and lower endogenous carbohydrate oxidation rates as compared to ingestion of 90 g h−1 in 1:2 ratio, which is the currently recommended approach for exercise of this duration. Methods Eleven male participants (V̇O2peak 62.6 ± 7 mL kg−1 min−1, gas exchange threshold (GET) 270 ± 17 W and Respiratory compensation point 328 ± 32 W) completed the study involving 4 experimental visits consisting of 3 h cycling commencing after an overnight fast at an intensity equivalent to 95% GET. During the trials they received carbohydrates at an average rate of 120 or 90 g h−1 in 0.8:1 or 1:2 fructose-maltodextrin ratio, respectively. Carbohydrates were naturally high or low in 13C stable isotopes enabling subsequent calculations of exogenous and endog...
A dose of fructose induces oxidative stress during endurance and strength exercise
Journal of sports sciences, 2009
This study sought to compare the time course changes in oxidative state and glycemic behavior when glucose or glucose plus fructose are consumed before endurance and strength exercise. After two weeks on a controlled diet, 20 physically trained males ingested an oral dose of glucose or glucose plus fructose, 15 min before starting a moderate-intensity 30min session of endurance or strength exercise. The combination resulted in four randomized interventions: glucose or glucose plus fructose þ endurance exercise and glucose or glucose plus fructose þ strength exercise, which were implemented consecutively in random order at 1-week intervals. Plasma concentration of lipoperoxides, oxidized LDL, reduced glutathione, catalase and glycemia were determined at baseline, during exercise and acute recovery. Following the ingestion of glucose plus fructose, lipoperoxides, catalase and reduced glutathione depletion were significantly higher than following consumption of glucose, for both endurance and strength exercise (P 5 0.05). Oxidized LDL-c was higher after glucose plus fructose than after glucose alone in endurance exercise (P 5 0.05). There was no difference in the glycemic peak between glucose plus fructose and glucose ingestion in endurance exercise trials. In strength exercise, the post-absorptive glycemic peak was less when the participants ingested glucose plus fructose than glucose (P 5 0.05), and a second peak was found in the recovery phase of this group (P 5 0.05). In conclusion, the addition of fructose to a pre-exercise glucose supplement triggers oxidative stress.
Metabolic availability of oral glucose during exercise: A reassessment
Metabolism, 1992
The purpose of this study was to reassess the metabolic availability of oral glucose during prolonged exercise in man, using 13C-labeling and a computation procedure (J Appl Physiol 69:1047-1052, 1990) that correctly takes into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates (Rendo). These changes are due to glucose ingestion associated with exercise. Each of the seven subjects completed three 2-hour periods of exercise at 67% maximum oxygen consumption (VO2max) on an ergocycle, with ingestion of water (1,000 mL) or 60 g (in 1,000 mL water) of 13C-labeled glucose at two levels of enrichment (13C/12C = 1.11482% and 1.13303%). As expected, Rendo significantly increased from rest to exercise with water ingestion (1.09888% +/- .00196% to 1.09970% +/- .00175%) and with glucose ingestion (1.10002% +/- .00159%) due to changes in the respective contributions of endogenous carbohydrates and fat to energy requirements as assessed by the respiratory exchange ratio (RER). When changes in Rendo were taken into account, the estimated amount of exogenous glucose oxidized was 38.8 +/- 10.3 g. Much higher values were found when Rendo at rest or during exercise with water ingestion were used in the computation (42.3 +/- 10.3 to 65.1 +/- 20.5 g) according to the commonly used method. Examination of data in the literature indicates that the reported oxidation rate of exogenous glucose (g/min) is significantly related to oxygen consumption (VO2) (L/min; r = .592) and that exogenous glucose contributes approximately 14% to 17% to the energy requirement.(ABSTRACT TRUNCATED AT 250 WORDS)
Clinical Science, 2009
The metabolic response when aerobic exercise is performed after the ingestion of glucose plus fructose is unclear. In the present study, we administered two beverages containing GluF (glucose + fructose) or Glu (glucose alone) in a randomized cross-over design to 20 healthy aerobically trained volunteers to compare the hormonal and lipid responses provoked during aerobic exercise and the recovery phase. After ingesting the beverages and a 15-min resting period, volunteers performed 30 min of moderate aerobic exercise. Urinary and blood samples were taken at baseline (t −15 ), during the exercise (t 0 , t 15 and t 30 ) and during the recovery phase (t 45 , t 75 and t 105 ). Plasma insulin concentrations were higher halfway through the exercise period and during acute recuperation (t 15 and t 75 ; P < 0.05) following ingestion of GluF than after Glu alone, without any differences between the effects of either intervention on plasma glucose concentrations. Towards the end of the exercise period, urinary catecholamine concentrations were lower following GluF (t 45 ; P < 0.05). Plasma triacylglycerol (triglyceride) concentrations were higher after the ingestion of GluF compared with Glu (t 15 , t 30 , t 45 and t 105 ; P < 0.05). Furthermore, with GluF, we observed higher levels of lipoperoxides (t 15 , t 30 , t 45 and t 105 ; P < 0.05) and oxidized LDL (low-density lipoprotein; t 30 ; P < 0.05) compared with after the ingestion of Glu alone. In conclusion, hormonal and lipid alterations are provoked during aerobic exercise and recovery by the addition of a dose of fructose to the pre-exercise ingestion of glucose.
Effects of Carbohydrate (CHO) and fat supplementation on CHO metabolism during prolonged exercice
Metabolism Clinical and Experimental, 1996
The aim of the study was to examine carbohydrate (CHO) utilization in subjects receiving CHO or CHO + medium-chain triglycerides (MCT) supplements during 180 minutes of exercise at 50% maximal aerobic work rate ([Wmax] 57% maximal oxygen consumption [Vo2max]). In a double.blind crossover design, nine trained athletes cycled four times. Subjects received a bolus of 4 mL • kg-1 at the start and 2 mL • kg -1 every 20 minutes during exercise of either a 150-g • L -1 CHO solution {CHO trial), an equicaloric 70 energy% (en%] CHO-30 en% MCT suspension containing 29 g MCT (CHO + MCT trial), or a 150-g • L -I CHO (high-CHO [HCHO]) solution plus 29 g MCT (HCHO + MCT trial]. A fourth trial consisted of a 13C-background control trial (CON}. The four trials were randomized. Before and after the exercise bout, muscle biopsies were taken from the quadriceps muscle and muscle glycogen levels were determined. During exercise, breath sam pies were collected for estimation of exogenous and endogenous CHO oxidation. No significant differences were detected in glycogen breakdown among the trials (277 -+ 14 14 mmol -kg dry weight -1 CHO, 249 -+ 20 CHO + MCT, and 240 -+ 18 HCHO + MCT) or in the respiratory exchange ratio during exercise. Mean exogenous CHO oxidation rates during the final hour of exercise were 0.79, 0.63, and 0.73 g • min -1, respectively. No differences were observed between the trials regarding exogenous or endogenous CHO oxidation. Plasma free fatty acid (FFA) concentrations were elevated during exercise to a level of approximately 500 pmol • L -1 and were comparable in all trials, whereas plasma ketone concentrations significantly increased after MCT ingestion as compared with the CHO trial. It is concluded that 29 g MCT co-ingested with CHO during 180 minutes of exercise does not influence CHO utilization or glycogen breakdown.
2008
Background: Consumption of a mixed meal increases postprandial carbohydrate utilization and decreases fat oxidation. On the other hand, acute endurance exercise increases fat oxidation and decreases carbohydrate utilization during the post-exercise recovery period. It is possible that the resulting post-exercise increase in circulating nonesterified fatty acids could attenuate the ability of ingested carbohydrate to inhibit lipid oxidation. The purpose of this study was to determine whether prior exercise attenuates the usual meal-induced decline in lipid oxidation.