Lunch dietary GI does not affect cognition of schoolchildren

Dietary glycaemic index (GI) consumed at lunchtime does not appear to have short-term effects on cognitive function in schoolchildren, a recent study has shown.

The investigators carried out a randomized crossover study at a comprehensive school on two test days. A total of 189 fifth and sixth graders were randomly assigned to one of two sequences: medium-high GI (m-hGI) or high-medium GI (h-mGI), following block randomization.

One group received a dish containing hGI rice (GI: 86) ad libitum in the first period, the other mGI rice (GI: 62); in the second period 1 week later, vice versa. The investigators performed a computerized test battery 45 min after beginning of lunch break to test tonic alertness, task switching, and working memory updating.

The t test was used for normally distributed data or the Wilcoxon rank-sum test for non-normally distributed data to estimate treatment effects.

The crossover approach showed that lunch dietary GI had no effects on the tested cognitive parameters in the early afternoon. Carryover effects, however, were determined for two parameters. Therefore, analysis was done only on data of the first period.

Of note, the hGI group demonstrated faster reaction time (p=0.001) of the two-back task (working memory updating) and lower count of commission errors (p=0.04) in the alertness task.

“Potential positive effects on single parameters of working memory updating and tonic alertness favouring hGI rice need to be verified,” the investigators said.