A Systematic Review and Metaanalysis on the Effects of

Hypertension affects 1 in 3 adults worldwide1 and contrib-utes to 51 % of deaths due to stroke and 45 % of deaths due to coronary heart disease.2 Low adherence to antihypertensive medication is com-mon and contributes to poor blood pressure (BP) control and adverse outcomes.3 In the United States, more than 36% of adults treated for hypertension have uncontrolled BP.4 Low patient adherence to antihypertensive medication is the most significant, modifiable, patient-related barrier to achieving controlled BP.5 Since dissatisfaction with conventional antihypertensive treatment is common, use of complementary and alternative treatment for hypertension is increasing.6 Garlic preparations, as a possible form of complementary alternative medicine, are among the most popular forms of herbal supplements in the United States.7 The 2002 US National Health Interview Survey showed that 421 of 10,525 (4%) persons with cardiovascular disease in the United States used garlic preparations.8 Garlic is claimed to have a moderate BP–reducing effect.9 A recently published metaanalysis of 11 randomized controlled trials on the effect of garlic on BP concluded that garlic preparations are better than placebo in reducing BP.10 However, only 4 of the 11 studies exclusively included indi-viduals with hypertension and the metaanalysis did not sys-tematically assess influence of trial quality on effect size. In this metaanalysis, we included recently published tri-als to evaluate the effect of garlic on BP in individuals with hypertension and systematically assessed risk of bias. METHODS Information sources and search We searched the electronic databases PubMed, Embase, Cochrane Library, and Web of Science using the search terms “garlic ” and “blood pressure ” or “hypertension ” from their inception through March 2014. Our search was then restricted to articles indexed as randomized clinical trials (for details of the search strategy in PubMed, see Supplementary material). There was no language restriction. We also searched tria