Jentjens, R. L., Achten, J., Moseley, L., & Jeukendrup, A. E. (2002). The effects of pre-exercise trehalose, galactose, and glucose ingestion on metabolism and cycling performance. Medicine and Science in Sports and Exercise, 34(5), Supplement abstract 1147.

"Glucose feedings in the hour prior to exercise can cause rebound hypoglycemia 15-30 minutes after the onset of exercise. . . Pre-exercise carbohydrates that produce minimal glycemic and insulinemic responsse have been suggested to be the preferred type of carbohydrate for consumption prior to exercise." This study examined the effects of pre-exercise ingestion of glucose, galactose, and trehalose on metabolic responses at rest and during cycling exercise, and on time trial performance. Trained male cyclists (N = 8) completed three exercise trials in random order. On each occasion, one of the experimental substances (75 g), along with 500 ml of water, was consumed 45 minutes before exercising for 20 minutes at submaximal steady state (65% of maximal power output) immediately followed by a time trial.

Plasma concentration and plasma insulin were significantly higher for glucose than the other two substances 15 minutes after ingestion. During submaximal work, rebound hypoglycemia was developed in the galactose and trehalose conditions. There were no differences in time trial performances between the groups.

Implication. Galactose and trehalose produce less rebound hypoglycemia than glucose and should be considered as a pre-exercise carbohydrate supplement.

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