||Last Updated: Apr 26th, 2007 - 09:55:10
Researchers from the University Hospital of Cologne pooled data from five studies of the effects of cocoa on blood pressure involving 173 participants, and found that consumption of cocoa had significant positive effects on blood pressure.
"The magnitude of the hypotensive effects of cocoa is clinically noteworthy; it is in the range that is usually achieved with monotherapy of beta-blockers or antiotensin-converting enzyme inhibitors," wrote the authors in the Archives of Internal Medicine.
Hypertension, defined as having a systolic and diastolic BP greater than 140 and 90 mmHg, affects about 600 million people worldwide and is associated with over seven million deaths.
"At the population level, a reduction of four to five mm Hg in systolic blood pressure [the top number, when the heart contracts] and two to three mm Hg in diastolic blood pressure [the bottom number, when the heart relaxes] would be expected to substantially reduce the risk of stroke (by about 20 per cent), coronary heart disease (by 10 per cent), and all-cause mortality (by 8 per cent)," they said.
The meta-analysis pooled data from 10 previously published trials, five of cocoa's effects on blood pressure and five involving green and black tea. All results were published between 1966 and 2006, involved at least 10 adults and lasted a minimum of seven days.
The studies were either randomized placebo-controlled trials, or used a crossover design, in which participants' blood pressure was assessed before and after consuming cocoa products or tea.
Of the 173 participants from the cocoa trials, 87 were assigned to consume cocoa and 86 were controls. Thirty-four per cent of the participants had hypertension. After an average follow-up of two weeks, a reduction in both systolic and diastolic blood pressure was observed in the cocoa-supplemented groups. Compared with controls, systolic blood pressure decreased by an average of 4.7 mmHg and diastolic blood pressure by 2.8 mmHg.
On the other hand, no such benefits were reported for the 343 individuals in the five tea studies (171 drinking tea and 172 controls).
The difference between tea and cocoa was related to the polyphenol content. While both are rich in polyphenols, black and green tea contain more flavan-3-ols, while cocoa contains more procyanids, said the reviwers.
"This suggests that the different plant phenols must be differentiated with respect to their blood pressure-lowering potential and thus cardiovascular disease prevention, supposing that the tea phenols are less active than cocoa phenols," wrote the authors.
The authors note the limitations of their study, including using a small number of studies with limited sample sizes and short follow-up.
"The findings of favourable hypotensive cocoa actions should however, not encourage common recommendations to consume more cocoa," said the authors. "We believe that any dietary advice must account for the high sugar, fat and calorie intake with most cocoa products."
"Rationally applied, cocoa products might be considered part of dietary approaches to lower hypertension risk," they concluded.
Confectionary giant Mars has been pro-active in research into the potential health benefits of flavanols from cocoa and has been sponsoring researchers in Germany and the US for about 15 years. Mars were not involved in this latest research.
CocoaVia, from Mars, and Acticoa, by Barry Callebaut, both boast high polyphenol content and are marketed as healthy options.
Source: Archives of Internal Medicine
9 April 2007, Volume 167, Pages 626-634
"Effect of cocoa and tea intake on blood pressure"
Authors: D. Taubert, R. Roesen, E. Schömig
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