Plain language summary
The aim of this study was to determine whether ingestion of low- rather than high-glycaemic index (GI) carbohydrate meals differentially affected cognitive performance immediately after eating (i.e. the 'postprandial period'). 21 individuals (65±7.3 years) with type 2 diabetes consumed 50g of either a low GI (pasta) or high GI (white bread) meal, or water on three separate mornings following an overnight fast. Cognitive function tests were administered and blood glucose levels were taken. Higher postprandial blood glucose (gAUC) was associated with poorer verbal memory recall. High GI consumption resulted in both higher gAUC and worse delayed verbal memory recall performance, compared to low GI consumption. Consuming 50g of a low-GI carbohydrate meal, relative to a high-GI carbohydrate meal, generally resulted in better cognitive performance in the postprandial period in adults with type 2-diabetes. The authors concluded that adults with type 2 diabetes are susceptible to poorer cognitive performance following ingestion of meals that result in large postprandial increases in blood glucose. Those with the highest postprandial increase in blood glucose showed the poorest memory performance. The authors recommended adopting diet strategies to minimise peaks in blood sugar.
Abstract
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.
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