Cognitive performance and its relationship with postprandial metabolic changes after ingestion of different macronutrients in the morning

The effect of carbohydrate, protein and fat ingestion on simple as well as complex cognitive functions and the relationship between the respective pos tprandial metabolic changes and changes in cognitive performance were studi ed in fifteen healthy male students. Subjects were tested in three sessions , separated by 1 week, for short-term changes in blood variables, indirect calorimetry, subjective performance and different objective performance tas ks using a repeated-measures counterbalanced cross-over design. Measurement s were made after an overnight fast before and hourly during 3 h after test meal ingestion. Test meals consisted of either pure carbohydrates, protein or fat and were served as isoenergetic (1670 kJ) spoonable creams with sim ilar sensory properties. Most aspects of subjective performance did not dif fer between test meals. For all objective tasks, however, postprandial cogn itive performance was best after fat ingestion concomitant with an almost c onstant glucose metabolism and constant metabolic activation state measured by glucagon:insulin (G:I). In contrast, carbohydrate as well as protein in gestion resulted in lower overall cognitive performance, both together with partly marked changes (P < 0.001) in glucose metabolism and metabolic acti vation. They also differently affected specific cognitive functions (P < 0. 05) in relation to their specific effect on metabolism. Carbohydrate ingest ion resulted in relatively better short-term memory and accuracy of tasks c oncomitant with low metabolic activation, whereas protein ingestion resulte d in better attention and efficiency of tasks concomitant with higher metab olic activation. Our findings support the concept that good and stable cogn itive performance is related to a balanced glucose metabolism and metabolic activation state.