Effects of breakfast glycaemic index and reactive hypoglycaemia on the course of memory and attention among young adults – relevance of chronotype

• Applicants: Professorin Dr. Anette Buyken; Professor Dr. Lars Libuda
• Subject Area: Nutritional Sciences
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 535607258

Breakfasts with a high glycemic index (GI) resulting in sharp rises in blood glucose may adversely affect memory and attention, particularly in the late postprandial phase (i.e., 120-180 minutes after breakfast). A recent meta-analysis suggests specific effects for immediate and delayed episodic memory among persons with a better glucose tolerance. Whilst young adults generally have a better glucose tolerance they are, however, prone to circadian misalignment since their midpoint of sleep (i.e., chronotype) is most delayed. This misalignment may also enhance glucose responses to high GI breakfasts among later chronotypes. Adding complexity, breakfasts inducing a "reactive hypoglycemia" (i.e., declines to levels below baseline) could also adversely affect memory and attention. Reactive hypoglycemia can result from both high GI foods and some low GI foods such as fruit juices. The overall aim of this project is to analyze the effect of (i) a high GI breakfast (study 1) and (ii) of a breakfast causing an (isolated) reactive hypoglycemia (study 2) on memory in the postprandial phase among young healthy university students. As recommended effects on attention will also be addressed. By conducting the studies on two samples of persons with an earlier and later chronotype subsequent analyses will inform on (iii) the postprandial course of glucose levels and the extent of reactive hypoglycemia per se, (iv) memory and attention in the postprandial phase and (v) breakfast food choices in these two groups. Study 1 and 2 are proposed as controlled, cross-over nutrition trials among 88 healthy university students (n=44 persons with earlier and n=44 persons with later chronotype). Study 1 will employ a high GI and a low GI beverage (glucose vs isomaltulose) and study 2 will employ two low GI beverages, one inducing a reactive hypoglycemia (glucose-fructose-sucrose, mimicking juice) and one not inducing a reactive hypoglycemia (isomaltulose). Memory and attention will be tested at -10, 90 (timing of expected reactive hypoglycemia in study 2) and 180 minutes (late postprandial phase). Glucose and insulin responses will be measured in capillary blood at -10, 0, 30, 60, 90, 120 and 180 min. The course of glycemic responses will be corroborated by continuous glucose monitoring devices (CGM). While aims (iii) + (iv) will be addressed in secondary analyses of the two studies, aim (v) will draw on dietary data assessed in the screening of 350 students preceding the studies to select persons with earlier and later chronotype. The project will provide novel mechanistic insights on the relevance of glycemic responses to breakfast for memory and attention in the postprandial phase among young adults. It will also be the first to elucidate the vulnerability of young adults with a later chronotype for the effects of breakfast GI on subsequent cognitive outcomes. Insights from this project will be directly relevant for public education settings for this age group.

• DFG Programme: Research Grants