Blood flow to the brain was boosted, and memory improved, among volunteers who drank just two cups of chocolate per day.
Experts hope the findings could lead to a cocoa-based treatment to protect against the killer brain disease.
Their research involved 60 people with an average age of 73 who were not suffering from dementia. The participants drank two daily cups of hot cocoa for 30 days and did not have any other chocolate.
They were tested for memory and thinking skills as ultrasounds measured their blood flow to the brain.
Eighteen members of the group were found to have impaired blood flow, but showed an average 8.3 per cent improvement after drinking hot chocolate for a month. Memory test scores also improved, with recall times falling from 167 seconds to 116 seconds on average.
The experts concluded that drinking hot chocolate regularly could help older people keep their brains healthy.
Dr Farzaneh Sorond, of Harvard Medical School in Boston, who led the study published online in the journal Neurology, said: “We’re learning more about blood flow in the brain and its effect on thinking skills.
“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.” Half the participants drank hot chocolate rich in antioxidants known as flavanols, while the other half received low-flavanol cocoa. The flavanol content made no difference to the results, it was found.
Dr Paul Rosenberg, from Johns Hopkins School of Medicine in Baltimore, said: “More work is needed to prove a link between cocoa, blood flow problems and cognitive decline. But this is an important first step that could guide future studies.”
From this small but interesting study, it seems that cocoa helps improve blood supply to the brain, therefore having a knock-on effect of improving people’s cognition
Dr Doug Brown, for the Alzheimer’s Society, said: “We know that poor blood flow can affect people’s brain power because they don’t have enough fuel in their brain cells to complete tasks efficiently.
“From this small but interesting study, it seems that cocoa helps improve blood supply to the brain, therefore having a knock-on effect of improving people’s cognition.
“This could be good news for those who enjoy a relaxing hot chocolate before bed, but we do need further research to better our understanding of the link between cocoa and cognition, and also whether it has any impact on dementia.”
Dr Simon Ridley, head of research at Alzheimer’s Research UK, said: “A cocoa-based treatment would likely be very popular, but it’s too soon to draw any conclusions about its effects.”