Effect of garlic on blood pressure: A systematic review and meta-analysis

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Non-pharmacological treatment options for hypertension have the potential toreduce the risk of cardiovascular disease at a population level. Animal tudies have suggested thatgarlic reduces blood pressure, but primary studies in humans and non-systematic reviews havereported mixed results. With interest in complementary edicine for hypertension increasing, itis timely to update a systematic review and meta-analysis from 1994 of studies investigating theeffect of garlic preparations on blood ressure.

We searched the Medline and Embase databases for studies published between 1955and October 2007. Randomised controlled rials with true placebo groups, using garlic-onlypreparations, and reporting mean systolic and/or diastolic blood pressure (SBP/DBP) and standarddeviations were included in the eta-analysis. We also conducted subgroup meta-analysis bybaseline blood pressure (hypertensive/normotensive), for the first time. Meta-regression analysiswas performed to est he associations between blood pressure outcomes and duration oftreatment, dosage, and blood pressure at start of treatment.

Eleven of 5 tudies included in the systematic review were suitable for meta-analysis.Meta-analysis of all studies showed a mean decrease of 4.6 ± 2.8 mm Hg for SBP in the garlic groupcompared to placebo (n = 10; p = 0.001), while the mean decrease in the hypertensive subgroupwas 8.4 ± 2.8 mm Hg for SBP (n = 4; p 0.001), and 7.3 ± 1.5 mm Hg or DBP (n = 3; p 0.001).Regression analysis revealed a significant association between blood pressure at the start of theintervention and the level of blood pressure reduction SBP: R = 0.057; p = 0.03; DBP: R = -0.315;p = 0.02).

Our meta-analysis suggests that garlic preparations are superior to placebo inreducing blood pressure in individuals with hypertension.



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