Published in the Annals of Neurology, the study utilized dietary surveys from approximately 6,200 women over age 65. As a follow up to the survey, the same women were interviewed five years later and asked to take cognitive functionality tests. The results indicated that those with diets highest in saturated fat had the worst scores related to reasoning and memory, while those with the highest monounsaturated fat intake had the best cognition test scores overall. Those who consumed mainly polyunsaturated fats, which are typically found in corn and vegetable oil, fell somewhere in between.
Those with diets high in saturated fat even appeared to show cognitive functioning ability of a theoretical brain age 5 to 6 years older than their biological age. Researchers suggest that one reason for the apparent difference could be that saturated fats may promote inflammation and damage to the arteries.