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Drinking two cups of hot chocolate a day may help older people keep their brains healthy, a U.S. study said Wednesday.

The study, published online in the American Academy of Neurology journal Neurology, involved 60 people with an average age of 73 who did not have dementia.

The participants drank two cups of hot cocoa per day for 30 days and did not consume any other chocolate during the study. They were also given tests of memory and thinking skills as well as ultrasounds tests to measure the amount of blood flow to the brain.

"We're learning more about blood flow in the brain and its effect on thinking skills," study author Farzaneh Sorond of the Harvard Medical School in Boston said in a statement. "As different areas of the brain need more energy to complete their tasks, they also need greater blood flow. This relationship, called neurovascular coupling, may play an important role in diseases such as Alzheimer's."

The researchers found that 18 of the 60 participants who had impaired blood flow at the start of the study saw an 8.3-percent improvement by the end of the study. There was no improvement for those who started out with regular blood flow.

The people with impaired blood flow also improved their times on a test of working memory, with scores dropping from 167 seconds at the beginning of the study to 116 seconds at the end, the researchers said. There was no change in times for people with regular blood flow.

A total of 24 of the participants also had Magnetic resonance imaging (MRI) scans of the brain to look for tiny areas of brain damage. The scans found that people with impaired blood flow were also more likely to have these areas of brain damage.

"More work is needed to prove a link between cocoa, blood flow problems and cognitive decline," said Paul Rosenberg, of the Johns Hopkins School of Medicine in Baltimore, who wrote an editorial accompanying the study. "But this is an important first step that could guide future studies."