Elevating blood glucose level increases the retention of information from a public safety video

Seventy-two undergraduates, 41 female and 31 male, aged 19-38, who had eaten breakfast had their blood glucose levels measured at 10.00 a.m. Following this they watched a presentation on safety when living away from home and had their recall of this material tested. Then half the participants imbibed a drink containing 50 g of glucose while the other participants imbibed a drink containing saccharine. A 20 min lecture followed to allow absorption and then blood glucose level was again measured and a second safety presentation was followed by another memory test. The two groups did not differ in initial blood glucose levels but only the group drinking the glucose drink had significantly elevated blood glucose at second test. The two groups did not differ in memory recall at the first test but the glucose drink group recalled approximately 20% more material after the drink. Analysis of covariance on the memory data with post-drink blood glucose level as a covariate attenuated the glucose effect suggesting that there is a relationship between glucose level and memory performance on this task. It is concluded that, although the precise mechanism by which enhanced memory performance occurs cannot be elucidated by these data, the results have practical significance for education. It is suggested that breakfast consisting of low glycaemic index foods may aid in challenging learning situations.