Metabolic effects of ingesting modified amylomaize starch during exercise

Abstract

The purpose of this study was to 1) determine if absorption takes place after ingesting HCL-ethanol modified amylomaize-7 by measuring the appearance of 13C plasma glucose; 2) determine if the starch was metabolically available by the appearance of 13C in expired C02; 3) determine if the ingestion of the starch during exercise, improves endurance performance as measured by time to fatigue. Ten male subjects cycled to fatigue at 60% V02 max preceded by the ingestion of high amylose modified starch (Amy 7), placebo (CON) or glucose (GLU). Protocol for ingestion started with a bolus feeding of 4 ml/kg at the start of exercise followed by ingestion of 2 ml/kg every 15 min for the duration of the exercise. Trials were separated by 1 week and treatments were administered in a random, double blind manner. The plasma glucose derived from erogenous carbohydrates (CHO) at the time of fatigue for the Amy 7, GLU and CON trials were 25% ± 2.6, 56.1% ± 2.9 and 14.7% ± 2.9 respectively. There was a significant difference between GLU and CON trials. The 13C exogenous oxidation rates for the Amy 7 trials were greater than CON trials but less than GLU. Maximum exogenous 13C oxidation rate for the GLU was 0.7 ± 0.04 g/min and for the Amy 7, 0.2 ± 0.04 g/min. Both GLU and Amy 7 trials were greater than CON trial and there was significant difference between the 3 trials. The mean times to fatigue for the 10 cyclists during the Amy 7, CON and GLU trials were 120.5, 114.7 and 134.1 min respectively with no significant difference between trials. The intermediate effect Amy 7 had on the 13C plasma glucose as well as the 13C exogenous oxidation rate (when compared to GLU & CON) indicates that Amy 7 was absorbed and metabolically available during 60% VO2 max exercise.