Expert sceptical about claims drinking hot chocolate reduces the risk of developing dementia

The head of research at Alzheimer’s Research UK has said it is “too soon to draw any conclusions” about a study claiming that cocoa – the key ingredient in chocolate – improves blood flow to the brain, and therefore reduces the risk of developing dementia.

Dr Simon Ridley notes the lack of a control group for comparison as a “drawback” of the research, which was carried out by doctors at Harvard Medical School and published yesterday.

They studied a group of 60 people over the age of 65, who were at high risk of vascular problems – 90 per cent were being treated for high blood pressures, 50 per cent had type 2 diabetes and 75 per cent were overweight or obese - but had no memory issues. Each participant drank two cups of cocoa a day for 30 days, with half drinking a variety with high levels of naturally occurring antioxidants called flavanols while the rest drank a cocoa with low levels.

The doctors measured the blood flow to the participants’ brains at the start of the study, one day after drinking the cocoa and then again on the last day of the 30-day study. They also carried out cognitive tests on the first and last days of the project, before giving each subject an MRI scan to look for changes in the brain’s white matter.

They found that 89 per cent of participants who had impaired blood flow at the start of the study saw improvements, compared to 36 per cent whose blood flow was classed as normal at the beginning of the research. The doctors also found there was no difference in results between those who drank flavanol-rich cocoa and those who had flavanol-poor cocoa.

Commenting on the research, Dr Ridley said: “This small study adds to a wealth of existing evidence linking vascular problems and poorer cognition. A cocoa-based treatment would likely be very popular, but it’s too soon to draw any conclusions about its effects. One drawback of the study 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. This research took place over a very short space of time, and it would be useful to see longer studies to investigate cocoa’s long-term effects.

“Dementia is one of the greatest medical challenges we face today, and it’s vital that we invest in research to find ways to prevent the condition. Poor vascular health is a known risk factor for dementia, and understanding more about the links between vascular problems and declining brain health could help the search for new treatments and preventions. In the meantime, evidence suggests we can lower the risk of dementia by eating a healthy, balanced diet with plenty of fruit and vegetables, exercising regularly, not smoking , and keeping cholesterol and blood pressure in check.”