Meal Composition and Cognitive Function

There is huge commercial and public interest in the capacity for foods to influence our psychological state, wellbeing, and cognitive function. Some dietary interventions have been leapt upon by the popular press and promoted to the consumer. The evidence for some of these recommendations is at best suggestive and demands critical scientific scrutiny. Consumption of certain macronutrients is thought to lead to metabolic and biochemical changes that may influence subsequent brain function, including cognitive function and appetitive response. This review draws on studies of the acute effects of meals and their macronutrient composition and on studies which examine the effect of varying the glycemic index of foods consumed on cognitive performance. Methodological and substantive issues related to the impact of nutrition on cognitive function in a number of different populations and with regard to time of day of ingestion are discussed. Cognitive function is strongly protected in healthy normal samples and enhancement of performance is widely reported following glucose manipulations, which provide readily available neural fuel. Some nutritional manipulations which exert different metabolic effects may result in no significant effects on mood, appetite, or cognitive performance. The magnitude of metabolic and/or biochemical changes that are required to induce or detect a change in cognitive function and the potential to suppress or compensate for changes in energy and macronutrient supply as result of nutritional manipulations with different glycemic indices are discussed. Some groups, e.g., children, diabetics or those with impaired glucose tolerance, and the elderly may be more vulnerable to nutritional manipulations than young healthy adults on whom much research is based. Time of day of ingestion of foods can impact on the metabolic and cognitive effects of meals. The methodological issues and differences between studies which do and do not demonstrate effects of nutritional manipulations on mental performance are critical to understanding potential effects of meals on mental performance and the claims which can be made for particular “functional foods.” Proposed edit to text - approved in the long-term or when consumed as a part of the habitual diet which merits further research, and some of these potentially valuable nutrient interventions are considered.