The 11 male and 11 female volunteers, ages 61-79 years, were administered a series of cognitive function tests after consuming drinks containing isolated protein, carbohydrate, or fat, or a placebo. The wide-ranging battery of tests was intended to assess general brain function, including verbal memory and other cognitive measures. The examinations were administered 15 and 60 minutes after the subjects finished the test drinks, and consisted of a word list recall test, a paragraph recall test, an attention test, and a "Trails" test in which subjects were asked to connect circled numbers in correct order. The ingestion of energy, regardless of its source, improved the participants' cognition, and the overall improvements were stronger for each drink 60 minutes following ingestion than for 15 minutes following ingestion. Test results showed a significant trend for the glucose only (carbohydrate) drink in improving the subjects' composite score in all testing at all time intervals.
Previous research has shown the beneficial effects of carbohydrate on memory performance. Nonetheless, the finding that protein and fat also enhance memory was novel, and a number of macronutrient-specific effects on brain function were noted. For instance, fat was the only macronutrient that tended to enhance attention, and the participants recalled more details 60 minutes after ingesting protein than they had remembered after only 15 minutes. The authors suggest that each macronutrient may improve performance via additional distinct mechanisms that are mediated by different brain regions.
An accompanying editorial by Morley points out that older people are much more vulnerable to cognition deficits due to poor diet, medications or disease, and a lifetime dietary pattern may influence cognitive changes during old age.
Kaplan, Randall J et al. dietary protein, carbohydrate, and fat enhance memory performance in the healthy elderly. Am J Clin Nut 2001;74: 687-93.
Morley, John E. Food for thought. Am J Clin Nutr 2001;74:567-8.
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