Eating mushrooms more than twice a week could prevent memory and language problems occurring in the over-60s, research from Singapore suggests.
A unique antioxidant present in mushrooms could have a protective effect on the brain, the study found.
The more mushrooms people ate, the better they performed in tests of thinking and processing.
But researchers said it was not possible to prove a direct link between the fungi and brain function.
The National University of Singapore study's findings were based on 663 Chinese adults, aged over 60, whose diet and lifestyle were tracked from 2011 to 2017.
Over the six-year study, the researchers found that eating mushrooms lowered the chances of mild cognitive impairment, so that roughly nine out of 100 people who ate more than two portions a week were diagnosed, compared with 19 out of 100 among those who ate fewer than one portion.
Mild cognitive impairment (MCI) can make people forgetful, affect their memory and cause problems with language, attention and locating objects in spaces - but the changes can be subtle.
It is not serious enough to be defined as dementia.
The participants in the study were asked how often they ate six different types of mushrooms: oyster, shiitake, white button, dried, golden and tinned.
Mushroom eaters performed better in brain tests and were found to have faster processing speed - and this was particularly noticeable in those who ate more than two portions a week, or more than 300g (10.5oz).
"This correlation is surprising and encouraging," said assistant professor Lei Feng, the lead study author, from the university's department of psychological medicine, reports BBC.
