A Meta-analysis
Background Epidemiological evidence suggests blood pressure–lowering effects of cocoa and tea. We undertook a meta-analysis of randomized controlled trials to determine changes in systolic and diastolic blood pressure due to the intake of cocoa products or black and green tea.
Methods MEDLINE, EMBASE, SCOPUS, Science Citation Index, and the Cochrane Controlled Trials Register were searched from 1966 until October 2006 for studies in parallel group or crossover design involving 10 or more adults in whom blood pressure was assessed before and after receiving cocoa products or black or green tea for at least 7 days.
Results Five randomized controlled studies of cocoa administration involving a total of 173 subjects with a median duration of 2 weeks were included. After the cocoa diets, the pooled mean systolic and diastolic blood pressure were –4.7 mm Hg (95% confidence interval [CI], –7.6 to –1.8 mm Hg; P = .002) and –2.8 mm Hg (95% CI, –4.8 to –0.8 mm Hg; P = .006) lower, respectively, compared with the cocoa-free controls. Five studies of tea consumption involving a total of 343 subjects with a median duration of 4 weeks were selected. The tea intake had no significant effects on blood pressure. The estimated pooled changes were 0.4 mm Hg (95% CI, –1.3 to 2.2 mm Hg; P = .63) in systolic and –0.6 mm Hg (95% CI, –1.5 to 0.4 mm Hg; P = .38) in diastolic blood pressure compared with controls.
Conclusion Current randomized dietary studies indicate that consumption of foods rich in cocoa may reduce blood pressure, while tea intake appears to have no effect.
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