Further evidence for a second meal cognitive effect. Evening meal glycaemic index manipulations are associated with cognitive performance in the evening and the next day

Abstract

Consumption of low glycaemic index (GI) foods at breakfast has been associated with cognitive benefits over the morning. However, the effects of evening meal GI manipulations on cognitive performance remain unexplored. The aims of the research were to investigate cognitive performance in the evening, and to replicate a previous finding that the GI of an evening meal is associated with cognitive performance the next morning following a standard breakfast, even after an overnight fast. Twenty-three healthy adults (16 females, 7 males) mean age 21.5 years (s.d. 2.4) consumed high GI (GI 83) and low GI (GI 28) evening meals matched for energy and macronutrients in a counterbalanced order following a cross-over, single-blind design. Memory, psychomotor skill and executive function were assessed 45 min post evening meal consumption and the next morning 15 min post consumption of a high GI breakfast (GI 88). Improved memory performance in the evening was associated with the low GI evening meal, whereas, improved memory performance the next day was associated with the high GI evening meal. This indicates that the cognitive effects of GI manipulations may differ in the acute postprandial phase relative to longer postprandial periods such as following a subsequent meal. Moreover, these findings provide further evidence for a second meal cognitive effect, indicating that an overnight fast may not be sufficient to control for any confounding effects of previous nutritional intake.