Postprandial Glycaemia and Cognitive Function

Abstract

Background: Previous research on the glycaemic index has suggested that low glycaemic index foods may have a positive effect on cognitive function. However, the body of literature on this topic has presented varying and contradicting results. This justifies further investigation of the relationship between glycaemic index and cognitive function. Objective: To determine the effects of glycaemic index on cognitive function by examining cognition after consumption of foods that differ only by the rate of digestion of glucose in a New Zealand population of young adults. Design: Double blinded, randomised, crossover, controlled trial. Methods: Sixty-five participants received a higher GI trifle sweetened with sucrose and lower GI trifle sweetened with isomaltulose on separate occasions. A battery of cognitive tests was completed prior to trifle consumption, and 60, and 120 minutes after. Fingerprick blood samples were taken coincident with the cognitive tests for the determination of blood glucose concentration. Results: There was no between-trifle difference at 60 minutes in performance on free word recall 0.0 (-0.6, 0.5), short delay work recall 0.0 (-0.5, 0.5), long delay word recall 0.0 (-0.6, 0.6), letter number sequence recall 0.3 (-0.2, 0.7) and visuo-spatial recall -0.2 (-0.6, 0.2) tests. At 120 minutes, no difference was detected in any of these tests. The participants performed 7.7 (14.9, 0.5) seconds faster in Reitan’s trail test B 60 minutes after the higher GI trifle than the lower GI trifle (P=0.037). Conclusion: The postprandial response to the glycaemic index of the test foods had no influence on memory. Performance on a task that combined multiple cognitive processes may be positively influenced by higher glycaemic foods 60 minutes after intake.