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Thursday, 8 August 2013

Sharpening memory and cocoa - how interested should you be?

Farzaneh Sorond and colleagues from Harvard and the Mass. General Hospital have attracted worldwide interest in their study published in the US journal Neurology "Neurovascular coupling, cerebral white matter integrity, and response to cocoa in older people". 

Listen to interview on the story on BBC local radio
The theme of the interest - from the LA Times to the Belfast Telegraph - is that cocoa "not only soothes the soul, but might also sharpen the mind'.
Fruit of the theobroma cocoa tree: Corti et al. Circulation 2009 
Why even think that it might? The authors drew on two background concepts:
- Earlier research using sophisticated brain imaging had reported that cocoa intake is associated with an increase in blood flow to the brain; and brain blood flow is linked to intellectual capacity.
- And cocoa contains flavonols, bioactive chemicals present in many foods associated with measures of healthy cardiovascular health, including increasing blood flow to the gray matter of the brain.
The question asked by the researchers was whether previous interest in chocolate containing products and better brain function might be explained by flavonol effects. 
To address this they carried out a study in which the design was high quality with regard to a possible effect of flavonols on 2 measures - brain blood flow and a test they used to assess memory.
What did they find? No difference in the effects of flavonol-rich vs low in flavonol cocoas as 2 cups per night for 30 days.
However, they reported a significant improvement in blood flow and in the intellectual function test by 30 days.
Should we all now start drinking large amounts of cocoa? Not yet based in this interesting but small study. To consider my question in a different way, key points arising from this work are:
- does cocoa sharpen the mind?
- does it protect from dementia?
- does it help people with dementia?
With these points in mind:
- the study was small - only 60 participants included and only 18 of these were noted to have improvements with regular cocoa
- the study was only for 30 days - more work would be needed to show whether these apparent benefits would be sustained
- the study was performed in older people - average age 73, who already had risk factors for cardiovascular disease - not safe to generalise study findings to other age groups and to people without cardiovascular risk factors.
- the 70% of volunteers who had normal blood flow and managed the test well at baseline should no improvement with cocoa
- the study was designed to test an effect of flavonols. However there was no time control for the effect of cocoa - e.g. vs other hot drinks. The authors cannot therefore rule out a time effect on their results e.g. people not managing the test well at the start doing better simply through  the initial practice
- the tests of brain function were 'Trailing Making Tests' ie involved a timed 'joining the dots' test. It would be important to confirm that more real world aspects of brain function were also improved
- no patients with dementia were included - further studies would be needed to show whether patients with dementia would also benefit and that any benefits were helpful for activities of daily living 
Thus results of the study could be explained as an artefact of the study design - ie not be due to the cocoa. At best they only applied to people with identified cardiovascular factors who also already had impaired brain blood flow and difficulty in performing the type of mental activity tests used by the researchers. 
And the concern about large amounts of cocoa is the associated increase in dietary sugar and fat intake of typical Western milky cocoa drinks. Neither are good for cardiovascular health, as they increase risk of overweight, high cholesterol, diabetes and high blood pressure. To compensate for those risks, the researchers under the strict conditions of the study made sure their volunteers made appropriate adjustments in other parts of the diet to balance sugar and fat intake over the month. In real world use, even if cocoa were confirmed to be helpful for the brain, it would be very important that people increasing their cocoa intake were very careful to avoid these unintended consequences of increased cocoa intake. Of note the researchers were not studying cocoa with added cream and marshmallows - not good for the circulation.
What about different sources of chocolate in cocoa? Not addressed by the researchers - except that they appeared to show at least that any benefits were not related to the types of flavonol they studied.
And how about eating chocolate instead? Again - not studied by the researchers. And in previous observational research on chocolate, there was an apparent benefit on heart disease protection from very small amounts (chocolate 1-3 times per month) with larger amounts reported to be harmful for the heart.
As a final thought, one of the reported uses by ancient Aztecs and Incas of chocolate drinks was as sedatives in religious rituals. Another explanation for the study findings is that calming effects of cocoa ('soothing the soul') reduced anxiety during the tests as a contribution to the observed improvements in brain blood flow and test performance with the drinks.

Link to interview 8.8.13 with Shane O'Connor on BBC local radio

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