Garlic Can Reduce Blood Pressure By Dr. John Briffa

Garlic is an oft-touted natural remedy, particularly regarding affairs of the heart. Regular garlic consumption has been said to improve cardiovascular health. In the past, one way it was believed to improve health was its ability to reduce blood pressure.

A previous review found seven trials in which the effects of garlic (powder) were compared with placebo: Three showed a significant reduction in systolic blood pressure (the higher blood pressure value), while four showed a significant reduction in diastolic blood pressure (the lower blood pressure value). Overall, the results indicated that garlic had genuine blood-pressure-lowering potential [1].

Since this review was published, other evidence has come to light. Recently, scientists brought the state of the science on this topic up to date with a meta-analysis, which combined the results of eleven relevant studies [2].

The results demonstrated the following: overall, a statistically significant reduction in systolic blood pressure (an average reduction of 4.6) and overall, no statistically significant reduction in diastolic blood pressure. [Blood pressure is measured in mmHg.]

The authors of this study also went on to separate out the data from individuals in studies who were deemed to have high blood pressure (blood pressure of 140/90 or higher).

In this group, the results showed a statistically significant reduction in systolic blood pressure (an average reduction of 8.4) and a statistically significant reduction in diastolic blood pressure (an average reduction of 7.3).

The authors point out that if the overall effect of garlic on blood pressure seen in the review was applied to the population as a whole, risk of cardiovascular disease and death from cardiovascular disease would be expected to fall by 8 percent to 20 percent. Perhaps it should be borne in mind that garlic might possibly reduce the risk of cardiovascular disease by other mechanisms as well, notably an anti-coagulant effect (garlic is a blood-thinner, like aspirin).

The dosages of garlic used in the studies on blood pressure were 600 mg to 900 mg. One of garlic’s main active ingredients is believed to be allicin. The dosages used in the studies would translate to a daily allicin dose of 3.6 mg to 5.4 mg. One single fresh clove of garlic contains 5 mg to 9 mg of allicin. For maximum effect, the garlic should be raw (uncooked).

References:

[1.] Silagy CA, et al. A meta-analysis of the effect of garlic on blood pressure.
Journal of Hypertension. 1994 Apr; 12(4): 463–8.

[2.] Ried K, et al. Effect of garlic on blood pressure: A systematic review and meta-analysis. BMC Cardiovascular Disorders 2008, 8:13 [Epub 16th June]

Dr. John Briffa is a London-based doctor and author with an interest in nutrition and natural medicine. Dr. Briffa's Web site

Last Updated
Oct 23, 2008