A "superfruit" famed for its health giving properties may protect ageing brains and help prevent Alzheimer's, new research suggests.
Bueberries, given in the form of a powder, were found to improve the thinking performance of 47 adults aged 68 and older who already had mild cognitive impairment, a risk factor for Alzheimer's.
A similar effect was not seen when volunteers were treated with a "dummy" placebo powder that was inactive.
Scientists plan to follow up the small preliminary study with a younger group of participants, including some considered to be at increased risk of the condition.
Lead researcher Dr Robert Krikorian, from the University of Cincinnati in the US, said: "There was improvement in cognitive performance and brain function in those who had the blueberry powder compared with those who took the placebo.
"The blueberry group demonstrated improved memory and improved access to words and concepts."
Magnetic resonance imaging (MRI) brain scans also showed increased brain activity in participants who had the blueberry powder.
The results were presented at the 251st National Meeting and Exposition of the American Chemical Society in San Diego, California.
Blueberries are packed with antioxidants and may lower the risk of heart disease and cell damage linked to cancer, it is claimed.
A second study included 94 people aged 62 to 80 who did not have measurable cognitive decline but reported experiencing memory loss. They were tested with blueberry powder, fish oil, and a placebo.
The results showed some thinking improvement for those given blueberry powder or fish oil, but little effect on memory.
One explanation might be that these participants had less severe issues than those in the first study, said Dr Krikorian.
The future research will involve people aged 50 to 65 including individuals who are obese, or have high blood pressure or cholesterol and considered at higher risk of dementia.