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Eating a daily dose of cocoa or dark chocolate may lead to a slight drop in blood pressure for a short period of time, a new systematic review suggests.
Pulling data from 20 studies published over the last decade, researchers found that people who ate flavanol-rich cocoa products every day for a few weeks saw their blood pressure drop by about two or three points.
"To me this says a little bit of dark chocolate isn't too bad, but you wouldn't want to go overboard with the kilojoules and eat a pound of chocolate," said Dr Elizabeth Jackson, a cardiologist and assistant professor of medicine at the University of Michigan Health Systems in Ann Arbor.
How the study was done
For the analysis, published in The Cochrane Library, Australian researchers searched several online databases to find randomised controlled trials that compared people eating flavanol-rich cocoa products to people eating low-flavanol cocoa powder or products that contained none of the plant compounds.
The 20 studies included in the review followed people who were generally healthy for two to 18 weeks.
Of 856 participants, 429 ate between 3 g and 100 g of dark chocolate or cocoa that contained anywhere from 30 mg to 1080 mg of flavanols, daily.
The other 427 people were put in comparison groups that ate low-flavanol cocoa powder or products that did not contain any flavanols.
At the end of the studies, those who ate the flavanol-rich dark chocolate or cocoa product saw their systolic blood pressure fall by roughly 2.8 mm Hg while their diastolic fell by 2.2 mm Hg.
Benefit in age
The link between flavanols and nitric oxide production could explain their benefit, researchers said.
However, the researchers cannot say anything about the effect of cocoa or chocolate consumption on blood pressure over months or years, nor can they connect flavanols to heart attacks and stroke risk.
The effects seemed greater in younger people compared to older adults.
Dr Jackson said that's not surprising since blood vessels may become less elastic as people age, and would be less likely to react to the nitric oxide.
The studies were also of varying quality, and overall the researchers said the quality of the evidence was low.
Still, the study's lead author Dr Karin Ried of the National Institute of Integrative Medicine in Melbourne, Australia, said that there may be a place for a bit of daily chocolate in a healthy lifestyle.
"Moderate regular dosages of flavanol-rich cocoa products such as dark chocolate may be part of a comprehensive lifestyle plan to optimising health," Dr Ried said.
(Reuters Health, August 2012)
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