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

Abstract

The effect of carbohydrate, protein and fat ingestion on simple as well as complex cognitive functions and the relationship between the respective postprandial metabolic changes and changes in cognitive performance were studied 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 tasks using a repeatedmeasures counterbalanced cross-over design. Measurements 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 similar sensory properties. Most aspects of subjective performance did not differ between test meals. For all objective tasks, however, postprandial cognitive performance was best after fat ingestion concomitant with an almost constant glucose metabolism and constant metabolic activation state measured by glucagon:insulin (G:I). In contrast, carbohydrate as well as protein ingestion resulted in lower overall cognitive performance, both together with partly marked changes P , 0´001 in glucose metabolism and metabolic activation. They also differently affected specific cognitive functions P , 0´05 in relation to their specific effect on metabolism. Carbohydrate ingestion resulted in relatively better short-term memory and accuracy of tasks concomitant with low metabolic activation, whereas protein ingestion resulted in better attention and efficiency of tasks concomitant with higher metabolic activation. Our findings support the concept that good and stable cognitive performance is related to a balanced glucose metabolism and metabolic activation state. Cognitive performance: Macronutrient ingestion: Postprandial metabolismThe relationship between postprandial metabolism and cognitive behaviour after macronutrient ingestion is only marginally characterised, and outcomes are not conclusive. Furthermore, there is little understanding of how the multitude of postprandial metabolic changes affect simple and complex cognitive functions as well as different mood states (for review, see Bellisle et al. 1998).The inconsistent results regarding macronutrient ingestion and cognitive behaviour can mainly be explained by methodological differences, such as consideration of baseline values or differences in time intervals of postprandial measurements, as well as by the difficulty in defining and differentiating indices to study. In most studies mixed meals high in one macronutrient were tested instead of pure macronutrient preparations, and interactions between macronutrients were not considered. Observed effects can not therefore be related unambiguously to a single macronutrient. Furthermore, the complex meals usually differed in energy content, volume and sensory properties (e.g. taste, pleasantness, texture), which may all influence behaviour and mental performance (Craig, 1986; Rogers, 199...

Ingesting breakfast meals of different glycaemic load does not alter cognition and satiety in children

“…Fischer et al 18 argued that stable cognitive performance is related to a balanced glucose metabolism and metabolic activation state. They reported that carbohydrate ingestion resulted in relatively better short-term memory and accuracy of cognitive tasks concomitant with low metabolic activation, whereas protein ingestion resulted in better attention and efficiency of tasks concomitant with higher metabolic activation.…”

Nutritional influences on cognitive function: mechanisms of susceptibility

“…However, other studies have found impaired performance with increasing arousal (Conners & Blouin, 1983), reduced arousal but no effect on performance (Lieberman et al 1983), better mood but no effect on performance for fed v. fasted subjects (Smith et al 1994c), or changes in performance but not mood (Smith et al 1988;Fischer et al 2001). This is perhaps not too surprising; causal relationships between mood and performance may well be neither contemporaneous (Owens et al 2000) nor linear: for instance, optimal attention or memory may require some, but not too much, arousal, alertness and anxiety (McGaugh, 1989;Smith, 1992;Reid & Hammersley, 1999).…”

“…However, that is unlikely to account for the impaired cognitive performance, since it has been found that a carbohydrate-rich diet actually improves some task performance, albeit only in neurotic subjects (Markus et al 1999). Nevertheless, a diet particularly low in some fats might impair cognition (see p. 180; Fischer et al 2001).…”

Diet, behaviour and cognitive functions: a psychobiological view

“…Cognitive impairment is associated with impaired glucose tolerance and hyperinsulinaemia in nondiabetic samples of elderly persons (29). Some studies suggest that stable performance is related to balanced glucose metabolism and state of metabolic activation (26). This may be mediated via an action of glucose on the cholinergic system (30).…”

“…Performance and the glycaemic index of foods Fischer et al (26) used test meals (400 kcal) of either pure CHO (glucose, maltodextrin and rice starch), protein or fat (a combination of saturated and unsaturated fatty acids). Protein ingestion resulted in better attention and efficiency on tasks, which was concomitant with higher metabolic activation.…”