Blood pressure and garlic

Garlic is often said to lower high blood pressure - that's something you read again and again. Should people with high blood pressure really reach for the strongly scented bulb more often, or the powders and granules made from it?

Contrary to popular belief, the studies on the blood-pressure-lowering effects of Allium sativum the botanical name for garlic are not so clear-cut.

In 2008, eleven different studies on garlic's effect on blood pressure were analyzed. Some studies did show better blood pressure reduction with garlic compared with placebo (the higher the starting blood pressure, the larger the possible reduction), but no consistent results could be found. This was partly due to insufficient methodological quality in some studies. For example, details on how blood pressure was measured during the study periods were often missing.

In 2010, Australian researchers studied the effect of socalled black garlic in patients with hard-to-control high blood pressure. Black garlic is regular garlic that has been aged by fermentation. The 50 participants took four capsules daily for twelve weeks containing black garlic extract (960 mg with 2.4 mg Sallylcysteine) or a matching placebo. The results showed a reduction in blood pressure, but it was not statistically significant.

A 2016 metaanalysis also showed a reduction in blood pressure values, although about one third of study participants did not respond to the garlic.

In 2019 another metaanalysis was published, looking at 12 studies in which participants took garlic as a powder or capsule or as aged garlic.
It found that garlic reduced participants' systolic blood pressure by an average of 810 mmHg and the diastolic pressure by about 56 mmHg. However, this effect was not seen in everyone; some participants fell short of these average reductions. This appears to be related to how well each person is supplied with B vitamins.
The analysis also showed that aged garlic had a beneficial effect on the arteries, specifically reducing arterial stiffness. It was also found that aged garlic, like other garlic preparations, has a bloodthinning effect, but it does not increase the risk of bleeding.

It is important to mention that garlic can interact with various medications. It can increase the antiplatelet (bloodthinning) effect of antiplatelet drugs, such as aspirin. Because an increased effect in this case a higher tendency to bleed is also possible when taken together with oral anticoagulants like Marcumar, as well as newer agents such as Xarelto, Eliquis, etc., garlic supplements are not recommended in these situations. On the other hand, garlic can reduce the effectiveness of protease inhibitors in people with HIV.

The 2019 metaanalysis confirmed a bloodpressurelowering effect of garlic. However, this effect was not observed in all participants. Some people respond to garlic with lower blood pressure, others do not. As that metaanalysis suggested, this may partly depend on B vitamin status. Taking the possible interactions into account, you can certainly enjoy fresh garlic as a food. Whether you should use a garlic supplement to lower blood pressure should be discussed with your treating physician first especially if you are already taking medication for high blood pressure.

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This article comes from BloodPressureDB – the leading app since 2011 that helps hundreds of thousands monitor their blood pressure every day. Our content is based on carefully researched, evidence-based data and is continuously updated (as of 03/2024).

Author Sabine Croci is a qualified medical assistant with many years of experience in internal medicine and cardiology practices as well as in outpatient care, and has led BloodPressureDB's specialist editorial team since 2015. Thanks to her extensive additional qualifications as a paramedic, first responder and in various therapy and emergency areas, she provides solid, practical and reliably reviewed information.

Blood pressure and garlic

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