Dietary protein, carbohydrate, and fat enhance memory performance in the healthy elderly

Background: Dietary carbohydrates can improve memory. Whether these effects are related to elevations in blood glucose or to energy ingestion is unkno wn. Objectives: Our objectives were to determine 1) the influence of isoenerget ic protein-, carbohydrate-, and fat-containing drinks on cognitive performa nce and 2) whether the time period after ingestion affects cognition. Design: After fasting overnight, 11 men and 11 women aged 61-79 y consumed either a 300-mL drink containing 774 kJ as pure protein (whey), carbohydrat e (glucose), or fat (safflower oil) or a nonenergy placebo on 4 separate mo rnings. Cognitive tests were administered 15 and 60 min after ingestion of the drinks. Plasma glucose and serum insulin concentrations were measured. Results: Only the carbohydrate drink increased blood glucose (P < 0.0001). Compared with the placebo, all 3 macronutrients improved delayed paragraph recall (PR) (P < 0.001) and improved or tended to improve immediate PR (P < 0.04) 15 min after ingestion. Beneficial effects on other cognitive tests were confined to one or more of the macronutrients: carbohydrate improved T rail Making Test (Trails) performance at 60 min (P = 0.02) and tended to im prove Trails at 15 min (P = 0.04) and PR at 60 min in men, carbohydrate and fat improved or tended to improve performance on Trails at 15 and 60 min i n subjects with poor baseline scores (r > -0.41, P < 0.03), fat tended to i mprove attention at 60 min P < 0.05), and protein reduced the rate of forge tting on the PR at 15 min (P = 0.002). Conclusions: Energy intake from protein, carbohydrate, or fat can enhance m emory independently of elevations in blood glucose. Each macronutrient may also exert unique effects on cognition.