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« on: May 10, 2007, 09:03:09 am » |
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April 11, 2007 — More happy justification for chocolate lovers: blood pressure (BP) responds favorably to cocoa, but not tea, a new meta-analysis suggests. Authors of the study say that while both products are rich in polyphenols, the study findings suggest that phenols in cocoa may be more active than those in tea. The study appears in the April 9 issue of the Archives of Internal Medicine.
"Products rich in cocoa may be considered part of a blood pressure lowering diet, provided that the total energy intake does not increase," lead investigator for the study, Dirk Taubert, MD, PhD, from the University Hospital of Cologne in Cologne, Germany, told heartwire. "I believe that cocoa is healthier than other sugar confectionary or high-fat dairy products."
Cocoa Beats Tea for BP
For their study, Taubert and colleagues conducted a literature search for randomized parallel group or crossover studies evaluating the effects of cocoa products or black or green tea for at least 7 days. They identified 10 studies that met their inclusion criteria: 5 randomized trials evaluated cocoa consumption (median, 2 weeks of cocoa consumption) in a total of 173 subjects and 5 trials evaluated tea consumption in a total of 343 subjects (in whom tea consumption was measured for a median of 4 weeks). In both analyses, study participants were evenly split between active and control groups. In the cocoa studies, cocoa consumption was typically flavonol-rich chocolate in the range of 100 g per day; in the tea studies, consumption was in the range of 4 to 6 cups daily.
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
Blood Pressure Pooled Change* (mm Hg) P
Cocoa
Systolic -4.7 .002
Diastolic -2.8 .006
Tea
Systolic 0.4 .63
Diastolic -0.6 .38
*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 ?-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."
Dr. Taubert believes his study "will not put the debate to rest, but foster a new debate and, more important, new research in this field."
Arch Intern Med. 2007;167:626-634.
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