Original Article
European Journal of Clinical Nutrition (2009) 63, 209–214; doi:10.1038/sj.ejcn.1602924; published online 10 October 2007
The effect of galactose supplementation on endurance cycling performance
Contributors: SRS was primarily responsible for and coordinated the execution of the study, performed the statistical analyses and drafted the manuscript. EJH performed the laboratory analyses and edited the manuscript. NS and SRS obtained the funding, and NS designed and prepared the intervention (sports drink) supplements.
S R Stannard1, E J Hawke1 and N Schnell2
- 1Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
- 2Fonterra Co-operative Ltd, Palmerston North, New Zealand
Correspondence: Dr SR Stannard, Institute of Food, Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North, New Zealand. E-mail: S.Stannard@massey.ac.nz
Received 29 April 2007; Revised 14 August 2007; Accepted 28 August 2007; Published online 10 October 2007.
Abstract
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.
Keywords:
carbohydrate, glycaemic index, exercise, cycling, insulin, free fatty acids
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