In the cocoa studies, systolic BP (SBP) and diastolic BP (DBP) dropped in the active group as compared with controls; however, in the tea studies, no differences were seen in BP between the 2 groups. The authors point out that while the 2 substances contain similar amounts of polyphenols, the components of these polyphenols differ between cocoa and tea: cocoa is particularly rich in procyanidins, whereas black and green tea are rich in flavan-3-ols and gallic acid. It may be that the polyphenol components in cocoa are more bioavailable, Taubert and colleagues propose.

Table. Change in Blood Pressure

*Compared with control group.
Source: Arch Intern Med. 2007;167:626-634.

According to Taubert and colleagues, the effects of cocoa on SBP and DBP were comparable to those achieved with antihypertensive drugs. "The magnitude of the hypotensive effects of cocoa is clinically noteworthy; it is in the range that is usually achieved with monotherapy of β-blockers or angiotensin-converting enzyme inhibitors," they write. "At the population level, a reduction of 4 to 5 millimeters of mercury in SBP and 2 to 3 millimeters of mercury 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%)."

Dr. Taubert acknowledged to heartwire that studies of tea and cocoa have yielded contradictory results. "The inconsistencies may result from differences in research question and research focus," he said. For example, "the reported effects of polyphenols on blood pressure, endothelial function, or platelet aggregation may be caused by different mechanisms and different phenols. The transient effects observed after administration of single phenol doses may be differentiated from the sustained effects observed after multiple daily doses. Moreover, plant foods like cocoa or tea contain many different — 100 and more — phenol compounds, but so far, mechanistic studies have focused on the flavonol monomers catechin and epicatechin, for which significant bioavailability has been demonstrated. But these may not be the active ingredients as our meta-analysis indicates."