Berries are good for the brain, according to a study that suggests the fruits can help fend off the mental decline of aging.

Women who ate one or more servings of blueberries or two or more servings of strawberries a week over two decades had minds that, based on memory tests, were 2.5 years younger than those who ate little to no berries, research today in the Annals of Neurology showed.

Blueberries and strawberries are rich in a type of flavonoid called anthocyanidins, which are known to cross from the blood into the brain and locate in the parts involved in learning and memory, said lead study author Elizabeth Devore. Flavonoids also may help mitigate the effects of stress and inflammation that could contribute to cognitive decline, she said. More studies are needed to confirm the findings, she said.

“There is very little known about flavonoids and memory, and virtually nothing known about long-term consumption of berries and flavonoids in relation to memory,” said Devore, an instructor in medicine at Brigham and Women’s Hospital and Harvard Medical School in Boston, in an April 24 e-mail. “This is really the first, large epidemiologic study of its kind. This is an exciting finding given that increasing berry intake is such a simple dietary modification.”

Researchers in the study included women from the Nurses’ Health Study who answered food questionnaires every four years beginning in 1980. Between 1995 and 2001, cognitive function was measured every two years in 16,010 participants who were 70 years and older.

In the study, one serving was equal to half a cup (118 milliliters).

They found that while berries appeared to help memory the most, other foods rich in flavonoids such as tea, onions and red wine, may also be helpful for memory, Devore said.

The authors said that the improved memory may also be the result of lifestyle choices like exercising more. Women in the study who consumed the most berries also had higher physical activity levels and annual household incomes, the study said.