Short-term effects of carbohydrates differing in glycemic index (GI) consumed at lunch on children’s cognitive function in a randomized crossover study

Abstract

Background 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. Methods 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. Results 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. Conclusion 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.

Water Consumption during a School Day and Children’s Short-Term Cognitive Performance: The CogniDROP Randomized Intervention Trial

“…Participants were excluded from analysis if they did not complete the study procedures for reasons such as not consuming any water or absence ( Figure 1). Gelsenkirchen, Germany, where nutrition intervention studies had been carried out successfully earlier [24][25][26]. Physical education-free days were chosen for the intervention.…”

“…Corresponding to our previous studies [24,26], a test battery was used, which was developed by the Institute for Work, Learning and Ageing (ALA) in Bochum, Germany, and adapted to the study conditions. Overall, four cognition tasks were performed in the sequence task switching, corsi block-tapping task, 2-back task, and flanker task ( Figure 2).…”

“…Reaction time (RT) for non-switch and switch trial in seconds (s) was measured. Switching costs were defined as difference in response time between the switch trial and the non-switch trial [26] and was calculated as follows:…”

“…Negative switch costs were excluded from the analysis (switch costs represent a positive respond time) [26,27]. .…”

“…In addition, a balanced drinking behavior of children is important, particularly because children's subjective feeling of thirst shows no correlation with fluid intake or hydration [6,7]. Measurements in of the 5 th and 6 th grade (fourteen classes) was undertaken at a comprehensive school in Gelsenkirchen, Germany, where nutrition intervention studies had been carried out successfully earlier [24][25][26]. Physical education-free days were chosen for the intervention.…”