We aimed to investigate the isolated effect of glycaemia on cognitive test performance by using beverages sweetened with two different glucose-fructose disaccharides, sucrose and isomaltulose. In a randomised crossover design, 70 healthy adults received a low-glycaemic-index (GI) isomaltulose and sucralose beverage (GI 32) and a high-GI sucrose beverage (GI 65) on two occasions that were separated by two weeks. Following beverage ingestion, declarative memory and immediate word recall were examined at 30, 80 and 130 min. At 140 min, executive function was tested. To confirm that the glycaemic response of the test beverages matched published GI estimates, a subsample (n = 12) of the cognitive testing population (n = 70) underwent glycaemic response testing on different test days. A significantly lower value of mean (95% CI) blood glucose concentration incremental area under the curve (iAUC) was found for isomaltulose, in comparison to the blood glucose concentration iAUC value for sucrose, the difference corresponding to -44 mmol/L∙min (-70, -18), p = 0.003. The mean (95% CI) difference in numbers of correct answers or words recalled between beverages at 30, 80 and 130 min were 0.1 (-0.2, 0.5), -0.3 (-0.8, 0.2) and 0.0 (-0.5, 0.5) for declarative memory, and -0.5 (-1.4, 0.3), 0.4 (-0.4, 1.3) and -0.4 (-1.1, 0.4) for immediate free word recall. At 140 min, the mean difference in the trail-making test between beverages was -0.3 sec (-6.9, 6.3). None of these differences were statistically or clinically significant. In summary, cognitive performance was unaffected by different glycaemic responses to beverages during the postprandial period of 140 min.
Keywords: cognition; fructose; glucose; glycaemia; insulinaemia; isomaltulose; sucrose.