Eating blueberries may protect ageing brains and help stave off symptoms of Alzheimer's disease, new research suggests.
Scientists from the University of Cincinnati in the US gave a group of volunteers either blueberries in a powder form or a placebo powder.
Blueberry powder was 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 ate a placebo powder, the Press Association reports.
MRI brain scans also showed increased brain activity in participants who had the blueberry powder, compared to ones who had the placebo.
Commenting on the findings, lead researcher Dr Robert Krikorian 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."
In a second study the researchers monitored the affect of blueberries, which are packed with antioxidants, on 94 people aged 62 to 80 who did not have measurable cognitive decline but reported experiencing memory loss.
The participants were tested with blueberry powder, fish oil and a placebo powder.
The results showed some thinking improvement for those given blueberry powder or fish oil, but little effect on memory.
According to Dr Krikorian, the difference in results may be due to the fact that the second wave of participants had less severe brain health issues than those in the first study.
Future research is set to 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.