Late night cocoa has never looked so appealing. A component of chocolate has been found to reverse age-related memory loss in healthy adults aged 50-69. The rejuvenating effect can be traced to increased blood flow in a specific region of the brain, say the researchers.

This is the first direct link that age-related forgetfulness is caused by changes in a specific part of the brain. It is also the first piece of evidence that memory decline can be reversed by a change in diet.

A specially prepared cocoa drink was fed to a sample of 37 older adults daily for three months. For some, the drink contained a large quantity of flavanols, which are found naturally in cocoa, tea and a wide variety of fruits and vegetables. For the others, the drink was largely free of the compound.

Pattern recognition tests found that those in the high-flavanol group had significantly improved memories at the end of the test than at the beginning. Brain scans showed that blood volume in a part of the brain called the dentate gyrus had also improved.

“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,” said Scott A Small, a professor of neurology and director of the Alzheimer’s Disease Research Center at the Taub Institute at Columbia University Medical Center.

Small is the lead author on the work, which was published online in Nature Neuroscience.

The results have been greeted with cautious optimism. “It would be very exciting if such a cognitive benefit of flavanols were shown in a larger study,” said Liz Coulthard, consultant senior lecturer in dementia neurology, University of Bristol.

Unfortunately guarding your memory is not as easy as remembering to eat more chocolate. Most methods of processing cocoa remove the flavanols. A typical chocolate bar contains about 40mg. The special drink used in the trial contained 900mg.

The drinks were prepared by chocolate manufacturer Mars Incorporated, who also partly funded the study. The Mars flavanol research programme began in the late 1980s to investigate the possible benefits to cardiovascular and cognitive health offered by the compounds.