Dark Chocolate May Help Control Elevated Blood Pressure...
July 1, 2010 — Dark chocolate may help control elevated blood pressure (BP), according to the results of a meta-analysis reported in the June 28 issue of BMC Medicine.
"Flavanols have been shown to increase the formation of endothelial nitric oxide, which promotes vasodilation and consequently may lower blood pressure," said lead author Karin Ried, from the University of Adelaide, Adelaide, Australia, in a news release. "There have, however, been conflicting results as to the real-life effects of eating chocolate. We've found that consumption can significantly, albeit modestly, reduce blood pressure for people with high blood pressure but not for people with normal blood pressure."
The goal of this meta-analysis was to review recent evidence on the effect of flavanol-rich cocoa products on BP in individuals with hypertension and in those with BP within the normotensive range. To identify randomized controlled trials of the effect of cocoa vs placebo on systolic and diastolic BP (SBP/DBP), the investigators searched MEDLINE, Cochrane, and international trial registries from 1955 to 2009. Minimal duration of included trials was 2 weeks.
For all studies meeting the inclusion criteria, the investigators performed random-effects meta-analysis. In addition, they performed subgroup analysis according to baseline BP being in the hypertensive or normotensive range. The relationship between type of treatment, dosage, duration, or baseline BP and BP outcome was examined with meta-regression analysis.
Selection criteria were met by 15 trial groups of 13 evaluated studies. Compared with placebo, cocoa-chocolate significantly lowered BP, according to a pooled meta-analysis of all trials, which showed a mean change in SBP of –3.2 ± 1.9 mm Hg (P = .001) and DBP of –2.0 ± 1.3 mm Hg (P = .003).
On the basis of subgroup meta-analysis, however, cocoa-chocolate had a significant effect vs placebo only in the hypertensive or prehypertensive subgroups (SBP: –5.0 ± 3.0 mm Hg; P = .0009; DBP: –2.7 ± 2.2 mm Hg; P = .01). In the normotensive subgroups, BP was not significantly decreased for cocoa-chocolate vs placebo (SBP: –1.6 ± 2.3 mm Hg; P = .17; DBP: –1.3 ± 1.6 mm Hg; P = .12).
"The practicability of chocolate or cocoa drinks as long-term treatment is questionable," Dr. Ried said.
Study design and type of control used were borderline significant, but possibly indirect, predictors for BP outcome, according to results of meta-regression analysis.
Limitations of this meta-analysis include high heterogeneity in the hypertensive subgroups. Effect sizes and levels of significance of the subgroup meta-analyses of trials with subjects with (pre-)hypertension at baseline should therefore be interpreted more cautiously.
"Our meta-analysis suggests that dark chocolate is superior to placebo in reducing systolic hypertension or diastolic prehypertension," the study authors write. "Flavanol-rich chocolate did not significantly reduce mean blood pressure below 140 mmHg systolic or 80 mmHg diastolic."
This study was supported by the Royal Australian College of General Practitioners (RACGP) 2006 Cardiovascular Health Research Grant, and the Australian Government Primary Health Care Research Evaluation Development (PHCRED) Program. The study authors have disclosed no relevant financial relationships.
BMC Medicine. Published online June 28, 2010. Abstract
อ่านเพิ่มเติมได้ที่ : Medscape CME (http://cme.medscape.com/viewarticle/724479?src=cmemp&uac=12159BG)
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