Aims/hypothesis  

Transient hyperglycaemia, consistent with that observed with normal meal ingestion, may be detrimental to cognitive performance in adults with type 2 diabetes. This study determined whether minimising the postprandial increase in blood glucose through the ingestion of low- rather than high-glycaemic-index (GI) carbohydrate meals differentially affected cognitive performance in the postprandial period.

Subjects and methods  

Using a within-individual design, 21 free-living subjects (65±7.29 years) with type 2 diabetes consumed 50 g carbohydrate as a meal with either a low GI (pasta) or a high GI (white bread), or water on three separate mornings following an overnight fast. Neuropsychological tests were administered and plasma glucose concentrations measured.

Results  

Higher postprandial blood glucose AUC (gAUC) was associated with poorer verbal memory (paragraph recall, p=0.01; word list recall, p=0.012). Both the GI of the carbohydrate meal and individual differences in response to meal ingestion contributed to the variation in gAUC and consequent memory recall. Bread consumption, relative to pasta, resulted in both a higher gAUC (p<0.05) and worse delayed verbal memory performance (paragraph recall, p=0.042; wordlist recall, p=0.035). Additionally, performance following bread consumption was poorer than that following pasta on measures of working memory, executive function and auditory selective attention, while sustained attention showed no sensitivity to type of carbohydrate food consumed.

Conclusions/interpretation  

Consuming 50 g of a low-GI carbohydrate meal, relative to a high-GI carbohydrate meal, generally results in better cognitive performance in the postprandial period in adults with type 2 diabetes, particularly in those individuals who experience the greatest food-induced elevations in blood glucose levels.