Metabolic response to [13C]glucose and [13C]fructose ingestion during exercise.
Seven healthy male volunteers exercised on a cycle ergometer at 50 +/- 5% VO2max for 180 min, on three occasions during which they ingested either water only (W), [13C]glucose (G), or [13C]fructose (F) (140 +/- 12 g, diluted at 7% in water, and evenly distributed over the exercise period). Blood glucose concentration (in mM) significantly decreased during exercise with W (5.1 +/- 0.4 to 4.2 +/- 0.1) but remained stable with G (5.0 +/- 0.4 to 5.3 +/- 0.6) or F ingestion (5.4 +/- 0.5 to 5.1 +/- 0.4). Decreases in plasma insulin concentration (microU/ml) were greater (P less than 0.05) with W (11 +/- 3 to 3 +/- 1) and F (12 +/- 4 to 5 +/- 1) than with G ingestion (11 +/- 2 to 9 +/- 5), and fat utilization was greater with F (103 +/- 11 g) than with G ingestion (82 +/- 9 g) and lower than with W ingestion (132 +/- 14 g). However F was less readily available for combustion than G; over the 3-h period 75% (106 +/- 11 g) of ingested G was oxidized, compared with 56% (79 +/- 8 g) of ingested fructose. As a consequence, carbohydrate store utilizations were similar in the two conditions (G, 174 +/- 20 g; F, 173 +/- 17 g; vs. W, 193 +/- 22 g). These observations suggest that, during prolonged moderate exercise, F ingestion maintains blood glucose as well as G ingestion, and increases fat utilization when compared to G ingestion. However, due to a slower rate of utilization of F, carbohydrate store sparing is similar with G and F ingestions.
D000328:Adult; D001682:Biological Availability; D001786:Blood Glucose / Q000378:metabolism; D002395:Catecholamines / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005632:Fructose / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism; D005082:Physical Exertion
D001786:Blood Glucose; D002395:Catecholamines; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007773:Lactates; D005632:Fructose; D019344:Lactic Acid; D006003:Glycogen; D005947:Glucose