NEW YORK (Reuters Health) - Garlic supplements may lower blood pressure just as effectively as some drugs used to treat hypertension can, according to a new research review.
"Supplementation with garlic preparations may provide an acceptable alternative or complementary treatment option for hypertension," Dr. Karin Ried and colleagues from The University of Adelaide in South Australia write.
Research to date on garlic and blood pressure has had "inconclusive" results, they note, while the last meta-analysis - in which the results of several studies are analyzed collectively -- only included studies done up until 1994.
To provide an updated perspective, Ried and her team included more recently published studies in their analysis, identifying 11 studies in which the patients were randomly assigned to garlic or placebo. In most studies, participants given garlic took it in powdered form, as a standardized supplement. Doses ranged from 600 mg to 900 mg daily, which study participants took for 12 to 23 weeks.
When the researchers pooled the data from the trials, they found that garlic reduced systolic blood pressure (the top number in a blood pressure reading) by 4.6 mm Hg, on average. An analysis limited to people with high blood pressure showed garlic reduced systolic blood pressure by 8.4 mm Hg, on average, and diastolic blood pressure (the bottom number) by 7.3 mm Hg. The higher a person's blood pressure -was at the beginning of the study, the more it was reduced by taking garlic.
The effects were similar to those of widely used drugs for treating hypertension, for example beta blockers, which reduce systolic blood pressure by 5 mm Hg, and ACE inhibitors, which produce an 8 mm Hg average drop in systolic blood pressure, the researchers note.
The 600 mg to 900 mg dosage used in the studies is equivalent to 3.6 mg to 5.4 mg of garlic's active ingredient, allicin, Ried and her team point out. A fresh clove of garlic contains 5 mg to 9 mg of allicin.
In the population as a whole, they note, reducing systolic blood pressure by an average of 4 to 5 points and diastolic blood pressure by 2 to 3 points could cut the risk of heart disease and heart disease-related death by up to 20 percent.
More research is needed to determine whether garlic supplementation might have a long-term effect on heart disease risk, the researchers conclude.
SOURCE: BMC Cardiovascular Disorders, published online June 16, 2008.