Scan any list of so-called superfoods and you'll find berries at the top. They're low in calories, fat free and a good source of fibre and vitamins.
But their superfood status is credited to their outstanding polyphenol content, natural compounds linked with anti-aging, anti-cancer and heart health benefits.
When it comes to anti-aging, previous studies have demonstrated the ability of strawberries, blueberries and blackberries to slow cognitive decline and improve memory in aged animals. It's thought that polyphenols protect the brain through their antioxidant and anti-inflammatory actions.
Now a new study presented this week at the 240th meeting of the American Chemical Society suggests that berries do more to keep your brain healthy as you age than fight harmful free radicals and dampen inflammation.
What to eat
It seems that a berry-rich diet can activate the brain's natural house-cleaning process, helping remove toxins and other compounds that can interfere with brain function.
Brain cells called microglia are responsible for the clean-up and recycling of toxic proteins, a process called autophagy.
In aging, however, microglia fail to do their work properly and toxic debris builds up. In addition, microglia become overactivated and actually begin to damage healthy brain cells.
In the study, researchers from the Human Nutrition Research Center on Aging at Tufts University in Boston exposed cultures of mouse brain cells to extracts of blueberries, strawberries and acai berries as well as walnuts, which are also rich in polyphenols. The extracts were the human equivalent to eating one cup of fresh berries or 14 walnut halves.
The berry and walnut extracts inhibited the action of a protein than normally shuts down autophagy and increased the levels of proteins that turn on the brain's house-keeping process.
The main source of polyphenols is your diet. While all berries and walnuts are excellent sources so are cherries, cranberries, plums, pomegranate seeds, prunes and red and purple grapes.
Other foods have also been shown to slow aging of the brain. Earlier this year, a large U.S. study revealed that individuals who had higher intakes of salad dressing, nuts, fish, chicken, tomatoes, fruit, cruciferous vegetables, leafy greens and lower intakes of high-fat dairy, red meat, organ meats and butter were 38 per cent less likely to develop Alzheimer's disease compared to those who adhered the least to this dietary pattern.
Another report concluded that a diet rich in fruit, vegetables, nuts, beans and olive oil guarded against Alzheimer's.