title: Exogenous carbohydrate oxidation from maltose and glucose ingested during prolonged exercise.
abstract: Intestinal perfusion studies have shown that glucose absorption from maltose occurs faster than from isocaloric glucose. To determine whether ingested maltose might be a superior source of carbohydrate (CHO) for endurance athletes, we compared the rates of gastric emptying, absorption and oxidation of 15 g.100 ml-1 solutions of maltose and glucose. Six endurance-trained cyclists drank 1200 ml of either U-14C maltose or U-14C glucose as a 400-ml loading bolus immediately before exercise, and as 8 x 100-ml drinks at 10-min intervals during a 90-min ride at 70% of maximal oxygen consumption. The rates of gastric emptying [maltose 690 (SD 119) ml.90 min-1; glucose 655 (SD 93) ml.90 min-1], the appearance of U-14C label in the plasma, and the peak rates of exogenous CHO oxidation [maltose 1.0 (SD 0.09) g.min-1; glucose 0.9 (SD 0.09) g.min-1] were not significantly different. Further, the 51 (SD 8) g of maltose and the 49 (SD 9) g of glucose oxidised during exercise were similar. Each accounted for approximately 20% of the total CHO oxidised during the 90 min of exercise. Since only half of the CHO delivered to the intestine was oxidised in the 90-min ride (maltose 49%; glucose 50%), we conclude that neither the rate of gastric emptying, nor digestion limited the rate of ingested CHO utilisation during the early stages of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, University of Cape Town Medical School, South Africa.
authors.forename: J A
authors.initials: JA
authors.lastname: Hawley
authors.forename: S C
authors.initials: SC
authors.lastname: Dennis
authors.forename: A
authors.initials: A
authors.lastname: Nowitz
authors.forename: F
authors.initials: F
authors.lastname: Brouns
authors.forename: T D
authors.initials: TD
authors.lastname: Noakes
mesh_terms: D000328:Adult; D050260:Carbohydrate Metabolism; D015444:Exercise / Q000502:physiology*; D005746:Gastric Emptying / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology; D007700:Kinetics; D008297:Male; D008320:Maltose / Q000378:metabolism*; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology
chemical_list: D008320:Maltose; D005947:Glucose