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 unknown.


OBJECTIVE
Our objectives were to determine 1) the influence of isoenergetic protein-, carbohydrate-, and fat-containing drinks on cognitive performance and 2) whether the time period after ingestion affects cognition.


METHODS
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), carbohydrate (glucose), or fat (safflower oil) or a nonenergy placebo on 4 separate mornings. 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 Trail Making Test (Trails) performance at 60 min (P = 0.02) and tended to improve 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 in subjects with poor baseline scores (r > -0.41, P < 0.03), fat tended to improve attention at 60 min (P < 0.05), and protein reduced the rate of forgetting on the PR at 15 min (P = 0.002).


CONCLUSIONS
Energy intake from protein, carbohydrate, or fat can enhance memory independently of elevations in blood glucose. Each macronutrient may also exert unique effects on cognition.
Kaplan
R J
RJ
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada. randall.kaplan@utoronto.ca
Greenwood
C E
CE
Winocur
G
G
Wolever
T M
TM
D000368:Aged; D001288:Attention / Q000187:drug effects / Q000502:physiology; D001786:Blood Glucose / Q000032:analysis; D003071:Cognition / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000494:pharmacology; D004041:Dietary Fats / Q000008:administration & dosage* / Q000494:pharmacology; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000494:pharmacology; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology; D008875:Middle Aged; D016037:Single-Blind Method; D013997:Time Factors
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D007328:Insulin