If you’ve been following the reports about garlic’s effect on blood pressure, you easily could be confused. First, garlic was reported to lower blood pressure, but recent studies failed to support the earlier claims. When conflicting results are reported from various sources, it’s best to wait for a comprehensive meta-analysis—an objective review of the results of many studies, using a similar set of criteria, to achieve a clear conclusion.
Now we have such a review of garlic for high blood pressure. News for the garlic lover is good. Researchers at the University of Adelaide in Australia conducted a meta-analysis of garlic studies published between 1955 and October 2007. Of the 25 studies the researchers found, 11 were reviewed. The 11 were the only studies with a placebo-control group; included supplements containing only garlic; reported mean systolic blood pressure and/or mean diastolic blood pressure; and included a standard deviation. The dose in the studies reviewed ranged from 600 to 900 mg per day, and the studies lasted 12 to 23 weeks.
After reviewing the data, the authors concluded that garlic supplements significantly lowered blood pressure (both systolic and diastolic) compared with a placebo for patients with high blood pressure. There was no significant difference in reducing either systolic or diastolic blood pressure in subjects within a normal blood pressure range at the outset of the studies. Larger-scale, longer-term clinical studies are needed to understand the potential of garlic for treating hypertension in a clinical setting.
For more information, see BMC Cardiovascular Disorders 8:13. Also see www.biomedcentral.com/1471-2261/8/13.