Breakfast, Glycemic Index, and Cognitive Function in School Children: Evidence, Methods, and MechanismsSandra I. Sünram-Lea
Breakfast has been claimed to improve cognitive function and academic performance, leading to the provision of breakfast initiatives by public health bodies. Children may be particularly sensitive to the nutritional effects of breakfast due to greater energetic needs compared to adults. However, there is a lack of acute intervention studies assessing what type of breakfast is optimal for cognitive performance. Dietary carbohydrates are of interest as they provide the main source of energy for the brain’s metabolic functioning, and there is mechanistic evidence linking postprandial glycemia to cognitive performance in both children and adult populations . Therefore, when considering what type of breakfast may be beneficial, the rate at which breakfast increases and maintains blood glucose, i.e., “the glycemic index” (GI) might be an important factor. Related to this is the concept of glycemic load (GL), which takes the amount of carbohydrates consumed into account. A review of studies investigating the optimal rate of glucose supply following breakfast consumption suggests that a lower postprandial glycemic response may be protective against a decline in cognitive performance over the morning. More specifically, findings to date suggest that beneficial effects of a low-GI or -GL breakfast are usually observed later in the morning. In terms of aspects of cognition, a low-GI or -GL breakfast was most consistently associated with beneficial effects on attention, but beneficial effects in memory and executive function have been observed . Although the evidence to date is promising, it is currently insufficient to allow firm and evidence-based recommendations. What limits our ability to draw conclusions from previous findings is that the studies have differed widely with respect to subject characteristics (age, sex, and habitual breakfast consumption), cognitive tests used, and timing of cognitive assessment. In addition, few studies have profiled glycemic response in children [3, 4]. There is, therefore, an urgent need for hypothesis-driven, randomized, controlled trials that evaluate the role of different glycemic manipulations on cognition. These should incorporate cognitive tasks that are sensitive to nutritional manipulations but also relevant to the specific learning situation encountered. Moreover, for future studies, multiple assessments at various time points, including baseline assessment and testing in the later period of the morning, are necessary to reveal the effects and time course of glycemic effects on cognition. Furthermore, there is a clear lack of intervention studies that employ ecologically valid research conditions, such as school-based testing. In addition, more data are needed in terms of the glycemic response to breakfast manipulation in children. These will also help to clarify the nature of the relationship between postprandial blood glucose concentrations and cognition (see Fig. 1 for important conceptual and methodological considerations when carrying out research into the effects of breakfast on cognition). Understanding the potential influence of breakfast interventions on children’s cognitive function remains a high priority given its application to learning and achievement at school. To date, the evidence is insufficient to allow firm conclusions as to what type of breakfast is most beneficial, but low-GI or -GL breakfasts which result in a lower postprandial glycemic response might be a promising strategy to optimize performance across the morning. However, further work is needed to substantiate this notion.
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