New neurological research suggests drinking cocoa every day might help older people keep their brains healthy.
A study of 60 elderly people with no dementia found two cups of cocoa a day improved blood flow to the brain in those who had problems to start with.
Those participants whose blood flow improved also did better on memory tests at the end of the study, according to a report in the journal Neurology.
Experts say, however, that more research is needed before firm conclusions can be drawn.
It is not the first time cocoa has been linked with vascular health - researchers believe that this is in part due to its being rich in flavanols, which are thought to have an important role.
In the latest study, the BBC reports, researchers asked 60 people with an average age of 73 to drink two cups of cocoa a day - one group given high-flavanol cocoa, another given low-flavanol cocoa - and consume no other chocolate. Ultrasound tests at the start of the study showed 17 of them had impaired blood flow to the brain.
There was no difference between those who drank flavanol-rich cocoa and those who had flavanol-poor cocoa. But whichever drink they were given, 88% of those with impaired blood flow at the start saw improvements in blood flow and some cognitive tests, compared with 37% of those whose blood flow was normal at the beginning of the study.
Neurovascular coupling the key
"We're learning more about blood flow in the brain and its effect on thinking skills," says study author Farzaneh Sorond a neurologist at Harvard Medical School.
"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 say the lack of difference between the flavanol-rich and flavanol-poor cocoa could be because another component of the drink was having an effect or because only small amounts were needed.
The head of research at Alzheimer's Research UK, Simon Ridley, says the study adds to a wealth of evidence but it's too soon to draw any conclusions about its effects.
"One drawback of this study," he says, "is the lack of a control group for comparison, and we can't tell whether the results would have been different if the participants drank no cocoa at all."