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Consciousness of Blood Pressure Is Rising as Details About Possible Remedies Continue to Evolve: Cocoa-Rich Foods, but Not Tea, May Lower Blood Pressure


Cocoa-Rich Foods, but Not Tea, May Lower Blood Pressure

Another study to raise the hopes (but not the blood pressure) of chocolate lovers everywhere has been published in JAMA.[19] The results of a meta-analysis by German researchers suggest that diets rich in cocoa can lead to significant reductions in SBP and DBP in the same range as those usually obtained with beta-blockers or angiotensin-converting enzyme (ACE) inhibitors. Consumption of green or black tea, however, had no apparent effect on blood pressure. Dirk Taubert, MD, PhD, and colleagues at the University Hospital of Cologne, like other researchers who have reported similar results, stress that their findings of the beneficial effects of cocoa do not extend to a recommendation to consume more cocoa products, which usually have high sugar and fat contents. Dr. Taubert and coauthors point out that there is a lack of guidance about cocoa and tea intake. "Cocoa and tea are currently not implemented in cardioprotective or anti-hypertensive dietary advice, although both have been associated with lower incidences of cardiovascular events," they say.

The researchers identified studies for their meta-analysis through searches of online databases, including MEDLINE, EMBASE, SCOPUS, and Science Citation Index, from 1996 to 2006 and other resources such as the Cochrane Controlled Trials Register. All the trials had a randomized or crossover design; examined 10 or more normotensive or hypertensive adults (at least 18 years of age); reported means and standard deviations or 95% confidence intervals of SBP and DBP at baseline and after the intervention; and provided type, duration, and amount of cocoa or tea consumption. All studies involved consumption of cocoa or tea for at least 7 days.

Five of the randomized controlled trials identified for the analysis studied the effect of cocoa on blood pressure and involved 173 participants, including 87 assigned to consume cocoa and 86 controls, 34% of whom had hypertension. They were followed for a median duration of 2 weeks. Four of the 5 trials reported a reduction in both SBP and DBP. Compared with those who were not consuming cocoa, SBP was decreased by an average of 4.7 mm Hg (P = .002) and DBP was decreased by an average of 2.8 mm Hg (P < .006). These effects are comparable to those achieved with blood pressure-lowering medications, the authors note.

"At the population level, a reduction of 4-5 mm Hg in SBP and 2-3 mm Hg in DBP would be expected to substantially reduce the risk of stroke (by about 20%), coronary heart disease (by 10%), and all-cause mortality (by 8%)," they say. The blood pressure-lowering effect of cocoa appeared greatest among the younger subjects with mild hypertension, whereas elderly hypertensives and younger normotensive subjects showed a smaller reduction. The amount of cocoa also appeared to be essential for the magnitude of the blood pressure reduction.

The 5 randomized, controlled trials of green or black tea intake involved 343 subjects with a median duration of 4 weeks. Drinking tea was not associated with a reduction in SBP or DBP in any of the trials. In 1 trial the lack of an effect may have been due to concomitant administration of antihypertensive medication, the authors suggest. This negative outcome was independent of age, presence of hypertension, or study duration. The effects of tea and cocoa were unaffected by ethnicity, sex, or body weight.

The blood pressure-lowering effect of cocoa-containing products can be attributed to the polyphenols they contain, the investigators suggest. Tea and cocoa are both rich in polyphenols, but while the main polyphenols in black and green tea are flavan-3-ols, gallic acid, and catechins, cocoa contains more of another type of polyphenol, procyanidins. "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," the authors conclude.

The investigators say that "rationally applied, cocoa products might be considered part of dietary approaches to lower hypertension risk." Anticipating the question of whether chocolate can ever be good for you, they allow that "it appears reasonable to allow phenol-rich cocoa products such as dark chocolate for calorie-balanced substitution of high-fat dairy produce, sugar confectionary, or cookies of the usual diet."

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