Blueberries and strawberries are good for the brain, according to a study that suggests that foods that contain high levels of flavonoids can slow the cognitive decline of aging.

The study, published in the journal Annals of Neurology, found that women who ate one or more servings of blueberries or two or more servings of strawberries a week over two decades delayed cognitive aging by up to 2.5 years, compared to those who ate little or no berries.

The study consisted of 16,010 women who were part of the Nurses' Health Study. Researchers had recorded the diets of all the women since 1980, and measured the mental function of participants aged 70 or over and who had not had a stroke between 1995 and 2001.

Researchers measured participant’s cognitive functioning during telephone interviews that were administered in 2-year intervals. Participants were asked to take memory tests like repeat details from a paragraph they had just listened to or to remember the order or words or numbers on a list, and researchers found that those who ate more berries had minds that were 2.5 years younger than those who didn’t. 

Researchers concluded that higher intake of flavonoids, compounds found in plants that have powerful antioxidant and anti-inflammatory properties, particularly from berries, appears to reduce rates to cognitive decline in older adults. 

Researchers explain that stress and inflammation both contribute to cognitive decline and increasing consumption of flavonoids could lessen the harmful effects. 

"We provide the first epidemiologic evidence that berries may slow progression of cognitive decline in elderly women," Dr. lead study author Elizabeth Devore at Brigham and Women’s Hospital and Harvard Medical School in Boston. "Our findings have significant public health implications as increasing berry intake is a fairly simple dietary modification to test cognition protection in older adults."

Although berries seemed to help memory the most, researchers said that other food that contain high amounts of flavonoids like tea, onions and red wine may also be helpful to memory. 

They cautioned that the findings linking improved memory to eating berries may also be the result of lifestyle choices, like exercising more or having a higher annual household income.