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Cocoa and the brain

by on 2013/09/02

People are rightly interested in lifestyle factors that might determine how their memory is likely to change as they get older, and a recent study published in the journal Neurology examined the association between consuming cocoa and brain function. When reported in the media, some outlets made reasonably bold sounding claims announcing that “Drinking hot chocolate could prevent Alzheimer’s by boosting blood flow to the brain” (the Daily Mail), although some were more measured (the BBC’s headline being “Cocoa ‘might prevent memory decline'”). So, should we up our cocoa consumption to reduce our risk of memory impairment?; let’s look at the study.

Why cocoa?

The researchers from various medical and brain imaging department based in Boston, USA, and led by Dr Farzaneh Sorond examined the effect of cocoa because it is rich in the antioxidant flavanol (although the actual content will vary according to the cocoa product), and its consumption has previously been reported as linked to better cognitive outcomes.

What did the researchers do?

Sixty participants were recruited for the study, all aged over 65 (the average age was 73 years old). At the first assessment, they completed some basic memory tests and blood flow to their brain was assessed. A particular focus for the researchers was to assess neurovascular coupling: when our brains need to work harder, they need more resources (oxygen and sugar delivered via the blood supply), and so blood flow to the brain is increased; the link between increasing activity in the brain and the blood flow increasing to meet this demand is called neurovascular coupling, and there is variation across individuals in how responsive they are to these changing demands.

After the baseline assessments, each participant was assigned to receive either flavanol-rich cocoa or flavanol-poor cocoa, and they were instructed to drink 2 cups of their allocated cocoa per day for 30 days. At the end of the month, the participants returned to the clinic for repeat memory tests and blood flow assessments.

What were the results?

First, the researchers reported that there were no differences across the cocoa-rich or poor groups in terms of blood flow to the brain so they were analysed as one group. In the main analysis, there were no changes in blood flow to the brain over the 30-day follow-up. That is, the consumption of two cups of cocoa per day did not increase blood flow to the brain over the month.

However, when the researchers divided the participants according to whether their neurovascular coupling was good or poor at baseline, those with poorer coupling initially showed improvement over: their neurovascular coupling improved, as did their scores on one of the memory tests.

And what did the researcher conclude?

One of the main conclusions was that poor neurovascular coupling could be improved, in this case with a cocoa-based intervention over a 30-day period. However, that result was based on the subgroup who had poor neurovascular coupling initially, numbering only 17 individuals. With such a small group, an effect might be observed because of something idiosyncratic in just a few participants, unrelated to the cocoa intervention.

What did the media say?

As noted, some media outlets made a connection between the results reported, and using hot chocolate as a potential dementia deterrent. That is not what the study reported, and indeed, the participants were all screened to ensure they were free from dementia.

Points to remember

The study was very small, and the main effect reported was only seen within the subgroup with poor neurovascular coupling at baseline. Importantly for a trial of this type, there was no control group, that is, a group of individuals who underwent all the same assessments but who didn’t get the intervention (cocoa). Furthermore, in terms of the improvement in memory reported, two memory tests were used but an improvement was only reported in one (and again, only in the small subgroup with poor initial neurovascular coupling).

The bottom line.

To return to the initial question, should we start increasing our cocoa consumption to reduce our risk of memory impairment?, based on this single study, the answer would be no.

Farzaneh A. Sorond, Shelley Hurwitz, David H. Salat, Douglas N. Greve, PhD & Naomi D.L. Fisher (in press). Neurovascular coupling, cerebral white matter integrity, and response to cocoa in older people. Neurology. doi: 10.1212/WNL.0b013e3182a351aa

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