Blueberries could protect middle-aged people from developing dementia, according to a new study.
The fruit contains high levels of micronutrients and antioxidants dubbed anthocyanins.
These give blueberries their namesake colour, but also protect them from radiation exposure and infections and could also stave off dementia.
Around 900,000 people are living with dementia in the UK and numbers are predicted to keep rising over the next 50 years.
One in three people born in the UK this year is expected to develop the condition within their lifetime unless better treatments become available.
Now scientists in the United States have come with a simple solution which could help keep Alzheimer's disease and other types of dementia at bay.
Professor Robert Krikorian at the University of Cincinnati said: "We had observed cognitive benefits with blueberries in prior studies with older adults and thought they might be effective in younger individuals with insulin resistance.
"Alzheimer's disease, like all chronic diseases of ageing, develops over a period of many years beginning in midlife."
Professor Krikorian, who has been studying the benefits of berries for several years, said: "These same properties that help blueberries survive also provide benefits to humans, such as reducing inflammation, improving metabolic function and enhancing energy production within cells."
The researchers recruited 33 patients from around Cincinnati who were overweight and whose blood sugar levels were higher than normal.
Participants were all aged between 50 and 65, and were starting to experience memory problems with ageing.
They were asked to abstain from consuming berries for a period of 12 weeks and given a packet of "supplement powder" to be drunk with a glass of water at breakfast or dinner time.
Half of the participants received powder packs containing the equivalent of one-half cup of whole blueberries, while the others were given a placebo.
They were also asked to complete a test designed to measure mental abilities known as executive functions, which play an important role in memory and self-control, and are known to deteriorate with age.
Professor Krikorian said: "Those in the blueberry-treated group showed improvement on cognitive tasks that depend on executive control.
"This was evident as reduced interference of extraneous information during learning and memory."
Those who were given blueberries also had lower levels of insulin, suggesting their metabolism was doing a better job of converting food into energy.
Taking blueberry supplements could therefore lower the chances of developing dementia later in life for thousands of people.
Next, the researchers are looking to better understand what mechanisms are behind the benefits of blueberries.
Professor Krikorian added: "The sample size is an obvious limitation of the study, so it will be important to reproduce these findings, especially by other investigators.
"In the meantime, it might be a good idea to consume blueberries on a regular basis."
The findings were published in the journal Nutrients.
