Abstract
BackgroundNon-pharmacological treatment options for hypertension have the potential to reduce the risk of cardiovascular disease at a population level. Animal studies have suggested that garlic reduces blood pressure, but primary studies in humans and non-systematic reviews have reported mixed results. With interest in complementary medicine for hypertension increasing, it is timely to update a systematic review and meta-analysis from 1994 of studies investigating the effect of garlic preparations on blood pressure.MethodsWe searched the Medline and Embase databases for studies published between 1955 and October 2007. Randomised controlled trials with true placebo groups, using garlic-only preparations, and reporting mean systolic and/or diastolic blood pressure (SBP/DBP) and standard deviations were included in the meta-analysis. We also conducted subgroup meta-analysis by baseline blood pressure (hypertensive/normotensive), for the first time. Meta-regression analysis was performed to test the associations between blood pressure outcomes and duration of treatment, dosage, and blood pressure at start of treatment.ResultsEleven of 25 studies 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 group compared to placebo (n = 10; p = 0.001), while the mean decrease in the hypertensive subgroup was 8.4 ± 2.8 mm Hg for SBP (n = 4; p < 0.001), and 7.3 ± 1.5 mm Hg for DBP (n = 3; p < 0.001). Regression analysis revealed a significant association between blood pressure at the start of the intervention and the level of blood pressure reduction (SBP: R = 0.057; p = 0.03; DBP: R = -0.315; p = 0.02).ConclusionOur meta-analysis suggests that garlic preparations are superior to placebo in reducing blood pressure in individuals with hypertension.
Highlights
Non-pharmacological treatment options for hypertension have the potential to reduce the risk of cardiovascular disease at a population level
Eleven of 25 studies included in our systematic review and investigating the effect of garlic on blood pressure met the inclusion criteria for meta-analysis (Table 1) [11,12,13,14,15,16,17,18,19,20,21]
A total of 252 individuals allocated to a garlic intervention group and 251 individuals allocated to a control group were included in the metaanalysis on SBP, and 283 versus 282 on diastolic blood pressure (DBP)
Summary
Non-pharmacological treatment options for hypertension have the potential to reduce the risk of cardiovascular disease at a population level. Animal studies have suggested that garlic reduces blood pressure, but primary studies in humans and non-systematic reviews have reported mixed results. With interest in complementary medicine for hypertension increasing, it is timely to update a systematic review and meta-analysis from 1994 of studies investigating the effect of garlic preparations on blood pressure. Updated guidelines for the treatment of high blood pressure stress the importance of preventive strategies, and recommend extending the management of blood pressure to include pre-hypertensive individuals (SBP 120–139/DBP 80–89 mm Hg) [1]. The increasing use of alternative and complementary therapies for hypertension [42,43] makes it timely to provide an updated systematic review and metaanalysis of trials investigating the effect of garlic preparations on blood pressure. Inclusion of additional data from studies published since 1994 has enabled subgroup metaanalyses of hypertensive and normotensive subjects
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