According to a team of scientists headed by Dr Scott Small of Columbia University, flavanols – naturally occurring bioactives found in the cacao plant, tea leaves and certain fruits and vegetables – can reverse age-related memory decline in healthy older adults.

As people age, they typically show some decline in cognitive abilities, including learning and remembering such things as the names of new acquaintances or where one parked the car or placed one’s keys.

This normal age-related memory decline starts in early adulthood but usually does not have any noticeable impact on quality of life until people reach their fifties or sixties.

Previous studies had shown that changes in a specific part of the brain called dentate gyrus are associated with age-related memory loss.

Until now, however, the evidence in humans showed only a correlational link, not a causal one.

To see if the dentate gyrus is the source of age-related memory decline in humans, Dr Small and his colleagues tested whether compounds called cocoa flavanols can improve the function of this brain region and improve memory.

In the study, 37 healthy volunteers (50-69 years old) were randomized to receive either a high-flavanol diet (900 mg of flavanols a day) or a low-flavanol diet (10 mg of flavanols a day) for three months.

Brain imaging and memory tests were administered to each participant before and after the study.

The brain imaging measured blood volume in the dentate gyrus, a measure of metabolism, and the memory test involved a 20-minute pattern-recognition exercise designed to evaluate a type of memory controlled by the dentate gyrus.

“When we imaged our research subjects’ brains, we found noticeable improvements in the function of the dentate gyrus in those who consumed the high-cocoa-flavanol drink,” said Dr Adam Brickman of the Columbia University’s Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, who is the first author of a paper published in the journalNature Neuroscience .

The high-flavanol group also performed significantly better on the memory test.

“If a participant had the memory of a typical 60-year-old at the beginning of the study, after three months that person on average had the memory of a typical 30- or 40-year-old,” Dr Small said.

“The findings need to be replicated in a larger study,” he added.

The scientists point out that the product used in the study – a cocoa flavanol-containing test drink prepared specifically for research purposes by the food company Mars Inc. – is not the same as chocolate, and they caution against an increase in chocolate consumption in an attempt to gain this effect.

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Adam M Brickman et al. Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults. Nature Neuroscience, published online October 26, 2014; doi: 10.1038/nn.3850