Research on pensioners found that drinking cocoa improved blood flow, which has been linked to healthier brains and improved cognition.
The study led by Harvard researchers examined 60 people with an average age of 73, who did not have dementia.
Participants drank two cups of hot cocoa per day for 30 days and did not eat any other chocolate.
They were given memory and thinking skills tests, as well as ultrasound tests to measure the amount of blood flow to the brain.
Of the 60 participants, 18 had impaired blood flow at the start of the study. The results of the study showed that for those participants, there were improvements in blood flow to the brain and in tests of their working memory.