Effect of a ketogenic meal on cognitive function in elderly adults: potential for cognitive enhancement

Rationale Glucose is the principal energy substrate for the brain, although ketone bodies are an effective alternative. Evidence suggests that elevation of plasma ketone body levels through oral intake of medium chain triglycerides (MCTs) may improve cognitive function. Objectives We tried to examine the possible effects of a ketogenic meal serving on cognition in elderly non-demented subjects. Methods Subjects were 19 non-demented elderly adults over 60 years old (13 females; mean age: 66.1 +/- 2.9 years) who underwent neurocognitive tests 90 and 180 min after oral intake of a ketogenic meal (Ketonformula (R)) containing 20 g of MCTs and an isocaloric placebo meal without MCTs on separate days. Results Elevation of plasma ketone concentration after intake of a single ketogenic meal containing 20 g of MCTs was confirmed (all p < 0.001). As for cognition, improvements were observed in the digit span test, Trail-Making Test B, and the global score (Z = -2.4, p = 0.017) following the ketogenic meal and the change in the executive functioning score was positively correlated with that of the plasma beta-hydroxybutyrate level. The cognition-enhancing effect was observed predominantly for individuals who had a relatively low global score at baseline (Z = -2.8, p = 0.005), compared to individuals with a high global score (Z = -0.7, p = 0.51). Conclusions Plasma levels of ketone bodies were successfully increased after intake of the ketogenic meal. The ketogenic meal was suggested to have positive effects on working memory, visual attention, and task switching in non-demented elderly.