Purpose <p>This study examined the effects of differential postprandial glucose responses on cognition in healthy older adults in a real-life setting. We hypothesised that consumption of a lower GI snack would have favourable effects on cognitive functioning and that this effect would be more pronounced in individuals with better glucoregulatory status.</p> Methods <p>Twenty-eight healthy adults, aged 50–65&#xa0;years, underwent two intervention periods of three consecutive test days, consuming either a low-GI snack or a control snack twice a day in a cross-over design. Cognitive performance and self-reported cognitive ability, mood, and appetite were measured six times on each of the six test days using a mobile application. Continuous glucose monitoring (CGM) occurred throughout the study. Glycated haemoglobin (HbA1c) and fasting glucose levels were taken as markers of glucoregulatory status.</p> Results <p>Consumption of the low-GI snack led to blunted post-prandial glucose responses but did not affect cognitive functioning. Significant interactions between the snack effect and glucoregulatory status were observed for Spatial Memory (p &lt; 0.01), Symbol Search (p &lt; 0.05), Composite Cognition score (p &lt; 0.05), and a trend for subjective cognitive ability (p = 0.07), indicating poorer effects of the low GI snack in subjects with poorer glucoregulation. Fluctuations in blood glucose parameters did not mediate the cognitive effects of the snacks or cognitive function fluctuations throughout the test days.</p> Conclusion <p>We demonstrated that poorer glucoregulatory status negatively affected the cognitive responses to a low-GI snack intervention. This interaction between glucoregulatory status and treatment response was detectable in non-diabetic subjects with normal to mildly compromised glucose regulation.</p> Trial registration <p>NCT05801731, 24-03-2023.</p>