effect of galactose supplementation on endurance cycling performance

• Published in: European journal of clinical nutrition Vol. 63; no. 2; pp. 209 - 214
• Main Authors: Stannard, S.R, Hawke, E.J, Schnell, N
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing Group 01.02.2009
• Subjects: Adult; athletic performance; Athletic Performance - physiology; Beverages; bicycling; Bicycling - physiology; Biological and medical sciences; Blood; Blood Glucose - metabolism; Carbohydrates; Cycling; dietary carbohydrate; Dietary Carbohydrates - pharmacology; Dietary supplements; Double-Blind Method; Exercise; Exercise - physiology; exercise endurance; Exercise Test; Fatty acids; Fatty Acids, Nonesterified - blood; Feeding. Feeding behavior; free fatty acids; Fructose; Fructose - pharmacology; Fundamental and applied biological sciences. Psychology; Galactose; Galactose - pharmacology; Gas sampling; Glucose; Glucose - pharmacology; glycaemic index; Glycemic index; Health aspects; Hexoses - pharmacology; Humans; Ingestion; Insulin; Insulin - blood; Lactic Acid - blood; Male; Medical sciences; men; Metabolic diseases; nutrition physiology; Nutrition research; Oxygen Consumption; Performance enhancement; Physical Endurance - physiology; Sports drinks; Sugar; Supplements; Vertebrates: anatomy and physiology, studies on body, several organs or systems; New Zealand; Performance evaluation; Physical exercise; Pancreatic hormone; Variations; Lipids; Metabolic diseases; exercise; cycling; free fatty acids; Free fatty acid; Insulin; Endurance; Carbohydrate; Supplementation; Galactose; Glycemia; glycaemic index
• ISSN: 0954-3007; 1476-5640; 1476-5640
• DOI: 10.1038/sj.ejcn.1602924

Objectives: This study tested the hypothesis that supplementation with galactose before and during endurance exercise would spare carbohydrate (CHO), optimize fat utilization and improve performance compared with a typical sports drink formulation. Subjects: Nine well-trained cyclists undertook three trials, each consisting of 120 min at 65 VO2max followed immediately by a set work, self-paced time trial (TT). Three treatments, allocated as a randomized balanced design, consisted of the following: (a) 8% (w/w) solution of galactose (Gal); (b) 8% solution of 50% galactose/50% glucose (Gluc/Gal); and (c) 8% solution of 80% glucose/20% fructose (Gluc/Fru). These were consumed as 0.67 g CHO per kg body wt 45-min pre-exercise; 1.0 g CHO per kg body wt per h for the first 120 min of exercise; 0.33 g CHO per kg body wt during the TT. Blood samples were collected before and during exercise; respiratory gas samples were collected only during fixed workload exercise. Results: Mean TT power output was significantly less in Gal compared with Gluc/Gal (P=0.030). Blood glucose and insulin concentrations were lower, and free fatty acids higher in Gal compared with Gluc/Gal and Gluc/Fru. Respiratory exchange ratio was not significantly different between trials. Conclusions: Ingestion of an 8% galactose-only solution (12.5 ml per kg body wt per h) is detrimental to endurance performance compared with equivalent volumes of iso-osmotic solutions containing 50% galactose/50% glucose or 80% glucose/20% fructose. This may reflect the inability of the liver to convert galactose into glucose at a rate required to support strenuous exercise intensity.