Abstract/Summary

Foods associated with a more favourable glycaemic response have been linked with cognitive benefits in acute settings in both the clinically healthy and those with type 2 diabetes. However, the current evidence is largely limited to examination of the effects of a single meal, particularly breakfast. Given that the daily human dietary pattern consists of multiple meals, the single meal paradigm fails to provide information about the glycaemic response and cognitive performance throughout the day. In addition, the glycaemic response following a meal has been shown to influence postprandial glycaemia and cognitive performance following a subsequent meal, which further illustrates the need to extend the current single meal investigation to a multiple meal testing paradigm. This thesis, therefore, aimed to investigate the relationship between the glycaemic response, cognitive performance and subjective mood across three consecutive meals in both clinically healthy and T2DM populations. Initially, two novel test meal profiles were designed using the glycaemic index concept with the aim of producing significantly different glycaemic profiles across the day; specifically, a Favourable (FGP) and Unfavourable (UGP) Glycaemic Profile. The two glycaemic conditions were then implemented in two randomised cross-over intervention studies in clinically healthy (n=40) and T2DM populations (n=25) to examine their effects on cognitive performance and subjective mood. Finally, a post-hoc analysis was performed to compare the glycaemic and cognitive outcome responses of the clinically healthy and T2DM populations. The FGP meals consistently produced a lower glycaemic response across the day in all samples. The clinically healthy population did not gain cognitive benefits from either condition, whereas the T2DM population displayed sustained cognitive performance during the FGP condition, particularly during the period after breakfast consumption. In addition, poor glucose regulators (defined via a glucose composite score) displayed worse cognitive performance than good glucose regulators within each population under an increased cognitive load. Finally, the glycaemic conditions had minimal impact on subjective mood. Taken together, these findings indicate that a more favourable glycaemic response profile over the course of several meals is associated with better cognitive performance in those with poorer glucose tolerance (i.e. T2DM) compared to an unfavourable glycaemic response profile. Longitudinal investigation of glycaemic control and cognitive performance in those with T2DM, using the multiple meal profiles developed in this thesis is suggested as future research. This would provide data on the extent, if any, of whether a long-term favourable glycaemic profile is associated with attenuation of cognitive impairment observed in those with T2DM.