The effect of postprandial glycaemia on cognitive function: a randomised crossover trial

Abstract

The effect on cognitive test scores of generating differences in postprandial glycaemia using test foods or beverages has been inconsistent. Methodological issues may account for some of the variable results requiring further investigation using strong study designs into the relationship between glycaemia and cognitive functioning. The objective of this study was to determine the effects of postprandial glycaemia on cognitive function by examining cognition after consumption of foods that differ only by the rate of digestion of available carbohydrate in a population of young adults. In a double-blind, randomised, crossover trial, sixty-five participants received trifle sweetened either with a higher-glycaemic index (GI) sugar (sucrose; GI 65) or a lower-GI sugar (isomaltulose; GI 34). Cognitive tests were completed prior to trifle consumption, and 60 and 120 min after. There was no between-trifle difference at 60 min in performance on free word recall (0·0 (95 % CI –0·6, 0·5)), short delay word recall (0·0 (95 % CI –0·5, 0·5)), long delay word recall (0·0 (95 % CI –0·6, 0·6)), letter–number sequence recall (0·3 (95 % CI − 0·2, 0·7)) and visuo-spatial recall (–0·2 (95 % CI –0·6, 0·2)) tests. At 120 min, no difference was detected in any of these tests. The participants performed 7·7 (95 % CI 0·5,14·9) s faster in Reitan’s trail-making test B 60 min after the higher-GI trifle than the lower-GI trifle (P = 0·037). Our findings of a null effect on memory are generally consistent with other works in which blinding and robust control for confounding have been used.

The effect of postprandial glycaemia on cognitive function – response to Young and Benton

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Letter to the EditorThe effect of postprandial glycaemia on cognitive functionresponse to Young and BentonWe would like to thank Young and Benton for their interest in our work. With reference to our study (1) , of the 98•8 g total available carbohydrate in the trifle, 60•4 g came from the added sugars (sucrose or isomaltulose). For glycaemic index (GI) testing, in which 50 g of available carbohydrate was used, this equated to 30•6 g of the test sugars.

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Glycaemic load and cognition: comments concerning Marchand et al.

“…An obvious suggestion is that the small difference in GL played a part in the present negative findings. Additionally, there is large interpersonal variability in postprandial glucose response to the same food (8) , although this was not considered by Marchand et al (1) . Studies that have considered individual glycaemic responses have often found this factor to be important (3) .…”

“…We read with interest the study by Marchand et al (1) who compared high and low glycaemic load (GL) trifles and found no significant effects on cognitive performance in young adults. As they suggest, this is a topic where there are inconsistencies due to differences in methodology.…”