Researchers linked to Harvard University have found that older women who ate too much red meat, butter and other foods that contain high levels of saturated fats had worse memories than others.
But, those who ate more monounsaturated fats -- found in olive oil, sunflower oil, seeds, nuts and avocados -- had better memories, the researchers said.
"When looking at changes in cognitive function, what we found is that the total amount of fat intake did not really matter, but the type of fat did," lead researcher Dr Oliva Okereke was quoted as saying by the Daily Telegraph.
Dr Okereke, who is from the Brigham and Women's Hospital in Boston which is affiliated to Harvard Medical School, and her fellow researchers made their conclusions after looking at results from 6,000 women aged over 65 years.
In the study, the participants subjected to a series of mental tests over four years and answered questionnaires about their diet and lifestyle.
"Substituting in the good fat in place of the bad fat is a fairly simple dietary modification that could help prevent decline in memory," Dr Okereke added.
More From This Section
Having a poor memory can be a harbinger of Alzheimer's in elderly people, although the former by no means always leads to the latter, the researchers said.
The study, published in the journal Annals of Neurology, follows other research showing a link between high cholesterol and a higher risk of developing Alzheimer's, the most common form of dementia.