Intervention studies suggest an influence of breakfast dietary glycemic index (GI) on children’s cognition. The Cognition Intervention Study Dortmund-GI-I study examined whether lunch dietary GI might have short-term effects on selected cognitive parameters.
A randomized crossover study was performed at a comprehensive school on 2 test days. One hundred and eighty-nine participants (5th and 6th grade) were randomly assigned to one of the two sequences, medium-high GI (m-hGI) or high-medium GI (h-mGI), following block randomization. In the first period, one group received a dish containing hGI rice (GI: 86) ad libitum, the other mGI rice (GI: 62)—1 week later, in the second period, vice versa. Tonic alertness, task switching, and working memory updating were tested with a computerized test battery 45 min after beginning of lunch break. Treatment effects were estimated using the t test for normally distributed data or the Wilcoxon rank-sum test for non-normally distributed data.
The crossover approach revealed no effects of lunch dietary GI on the tested cognitive parameters in the early afternoon. However, we determined carryover effects for two parameters, and therefore analyzed only data of the first period. The reaction time of the two-back task (working memory updating) was faster (p = 0.001) and the count of commission errors in the alertness task was lower (p = 0.04) in the hGI group.
No evidence of short-term effects of lunch dietary GI on cognition of schoolchildren was found. Potential positive effects on single parameters of working memory updating and tonic alertness favoring hGI rice need to be verified.
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The authors thank the participants and their teachers, the management of the school and the kitchen staff for supporting this study. The authors acknowledge the committed field work staff. Particular thanks to Jennie Brand-Miller and Fiona Atkinson from SUGiRS for GI measurements and to Ludger Blanke (ALA Institute) for advice on application and evaluation of the cognition test battery and the excellent technical support.
This study was supported by a grant from the Uniscientia Foundation, Vaduz, Liechtenstein. Uniscientia was not involved in the design, analysis or writing of this paper.
Conflict of interest
AEB is a member of the ILSI Europe Carbohydrate Task Force and a member of the International Carbohydrate Quality Consortium (ICQC). None of the authors have any personal or financial conflicts of interest.
The study was approved by the Ethics Committee of the University of Bonn and registered at clinicaltrials.gov (NCT02763371). All assessments were made in adherence to the Declaration of Helsinki.
Written informed consent was obtained from all participants and their parents or legal guardians.
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Jansen, K., Tempes, J., Drozdowska, A. et al. Short-term effects of carbohydrates differing in glycemic index (GI) consumed at lunch on children’s cognitive function in a randomized crossover study. Eur J Clin Nutr 74, 757–764 (2020). https://doi.org/10.1038/s41430-020-0600-0