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Dr JoAnn Elisabeth Manson comments on recent headlines claiming chocolate may prevent dementia

Tuesday 28 March 2017

There have been a number of recent media headlines, about chocolate pills and other forms of chocolate being able to prevent dementia. We asked Dr JoAnn Elisabeth Manson, Professor of Medicine at Harvard, to provide her comments.

Dr JoAnn Elisabeth Manson is Professor of Medicine, Harvard Medical School and Chief, Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital.

The focus of Dr Manson’s research has been women's health, randomised clinical trials in cardiovascular disease prevention, and population health/translational research.

Find out more about Dr Mason here:

Were the headlines right or were they misleading in some way?

The headlines suggest that chocolate has the ability to prevent Alzheimer’s. Like many other news headlines these days, the “headline” allegation is not directly linked to the findings of the study. The results of the investigation published in the journal Neurology, did not assess the effect of the consumption of hot chocolate on the conversion rate to Alzheimer’s, which would be needed in order to be able to make statements about “prevention”.

More specifically the scientists examined the participants’ performance in cognitive tasks and evaluated the relationship between local neural activity and subsequent changes in cerebral blood flow before and after the consumption of cocoa for 30 days and compared the results between participants that had consumed flavanol-rich cocoa (609 mg), and flavanol-poor cocoa (13 mg flavanols). Blood flow and blood pressure changes were not significantly different between the two cocoa groups. Therefore, the researchers evaluated whether or not the response to cocoa (without taking the amount of cocoa flavanols into account) differed depending on neurovascular coupling (NVC) status, indicating that there was a significant improvement for 17 people with a poor NVC status at baseline. Considering the small sample seize, the findings should be regarded as indicative rather than definitive.

This is another small study that suggests that the naturally occurring flavanols in cocoa beans may improve blood flow. But the first large long-term study to assess whether cocoa flavanols can lower the risk of heart attacks, strokes, memory loss, and other illnesses is on its way.

How important is this story/study for furthering dementia research? Should we be excited?

“Cocoa flavanols look promising,” said Dr Manson. “The next logical step is to move from the small randomised trials looking at mechanisms like changes in blood flow and blood pressure to testing whether cocoa flavanols can reduce the risk of clinical events—heart attacks, strokes, cardiovascular deaths.”

“People have had so many misconceptions about the study,” says Manson. “They think we’re testing chocolate or that the trial is a signal that they should eat more chocolate. It isn’t. “People can still eat chocolate for their enjoyment, but we don’t recommend that they eat more of it to get more flavanols.”

To get 750 mg of flavanols a day, you’d have to eat nearly 1,000 calories’ worth of dark chocolate or thousands of calories of milk chocolate every day. A more reasonable source: an unsweetened cocoa powder you can mix into your coffee, milk, yogurt, hot cereal, or other food - that is, if the cocoa hasn’t been processed in a way that destroys flavanols.

What are the next steps?

Dr Manson is co-directing the new trial - the COcoa Supplement and Multivitamins Outcomes Study (COSMOS) - which will give cocoa flavanols (750 mg a day) or a placebo to 18,000 women (aged 65 or older) and men (aged 60 or older) for four years. The trial is co-led by Howard Sesso, Associate Professor of Medicine at Harvard Medical School. “We’ll also look at cognitive function, diabetes, physical performance, and other outcomes,” explained Dr Manson.

But it’s not worth signing up so you can eat chocolate in the name of science. “It’s not a randomised trial of chocolate or even dark chocolate,” noted Dr Manson. “It’s a randomised trial of cocoa flavanols—bioactive plant-based nutrients with virtually no calories, sugar, or fat.” Why can’t you get the same 750 mg of flavanols from chocolate? “It would require an enormous amount,” she said. “And for many forms of chocolate, it would be virtually impossible because the cocoa flavanols are destroyed in processing.”

“In COSMOS, we’ll be giving people cocoa flavanols that were protected from the time that they were harvested from cocoa beans,” says Manson. “They come in a capsule, which makes it possible to do a long-term placebo-controlled trial and not add a load of sugar, saturated fat, and calories to the diet.”

(The study is funded by Mars Symbioscience, a division of Mars, Inc., with partial support from the National Institutes of Health.)

What might be the impact of this story/study in the scientific community?

The study will lead to a better understanding of the potential effects but also limits of cocoa consumption and add new knowledge to the scientific evidence that is gathered in the combat of diseases.