Could garlic be a reliable alternative therapy for the treatment of hypertension?

Following on from Monday’s post on hypertension I’ve been looking at the potential benefits of garlic as an alternative therapy for this condition.  I’ve spent the last few hours perched under the Oak Tree reading all about the ‘stinking rose’.  Known as much for its odour as well as its flavour, garlic’s scent comes primarily from sulphur compounds.  Allicin is one of these compounds and is also thought to be responsible for many of its health benefits.

Garlic is widely used for its blood pressure lowering effects and there is evidence to suggest that it may indeed be useful in the treatment of hypertension.  With so many people being diagnosed with this condition every year and the possibility that conventional treatment may not be beneficial to some, it is right that alternative and complementary therapies are explored.

A Cochrane systematic review has been carried out to determine the effect of garlic consumption on morbidity and mortality in hypertensive patients.  The study investigated whether garlic monotherapy provided a therapeutic advantage over placebo for the treatment of adults with hypertension by looking at all cause mortality, cardiovascular events (fatal or non-fatal heart attacks) and cerebrovascular events (fatal or non-fatal strokes).  Their secondary objectives were to quantify the blood pressure lowering effect of garlic consumption specifically in hypertensive patients.

After a search of relevant databases two randomised controlled trials (RCTs) were identified for inclusion. In the first RCT 47 hypertensive individuals used 200mg of garlic powder three times daily for 12 weeks versus placebo.  After meta-analysis this is what they found:

  • Garlic significantly reduces mean supine (inactive) systolic blood pressure by 12 mmHg (95% CI 0.56 to 23.44 mmHg, p= 0.04) and mean supine diastolic blood pressure by 9 mmHg (95% CI 2.49 to 15.51 mmHg, p=0.007) versus placebo
  • Clinical outcomes were not reported, however, the authors stated that garlic was “free from side effects” and that no adverse effects were reported.  Three cases were reported, “where a slight smell of garlic was noted”

In the second RCT hypertensive patients were given 200mg garlic powder three times daily for 12 weeks but they were also receiving hydrochlorothiazide-triamterene  baseline therapy.  This is what they found:

  • A mean reduction of systolic blood pressure by 10-11 mmHg and of diastolic blood pressure 6-8 mmHg versus placebo
  • No patients experienced any cardiovascular outcomes


  •  Meta-analysis could only be carried out on the first RCT as the second RCT did not report the number of people randomised to each group
  • There is a real lack of clinical trials that randomise hypertensive patients to either garlic or placebo so the magnitude of garlic’s effect on blood pressure cannot be properly quantified
  • The two trials had small sample sizes and did not report important methodology details
  • There is insufficient data on the clinical outcomes or adverse effects of garlic therapy

The authors concluded:

“Garlic appears to have a blood pressure lowering effect but the precise estimate of blood pressure reduction specifically in hypertensive individuals remains unknown.”

“In addition, evidence is lacking on the possible impact of garlic on mortality or cardiovascular morbidity. Future trials should randomise hypertensive patients to several doses of garlic versus placebo.  These trials should be large enough and report the differences in mortality, serious adverse effects and cardiovascular morbidity.”


This could be a really effective alternative treatment for hypertension but it is clear that much more work is needed in this field to clarify the benefits of garlic consumption.  Until that’s done maybe I’d better rethink my supper of garlic omelette with garlic roasted veg followed by garlic ice-cream and a, yes you guessed it, garlic wafer!  I don’t want to scare all the elves from the Woodland with my stinky breath!  A dose of garlic powder might be a little more civilised.


Stabler SN, Tejani AM, Huynh F, Fowkes C. Garlic for the prevention of cardiovascular morbidity and mortality in hypertensive patients. Cochrane Database of Systematic Reviews 2012, Issue 8. Art. No.: CD007653. DOI: 10.1002/14651858.CD007653.pub2.

Cochrane summary of this review

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Sarah Holloway

My name is Sarah Holloway. I am an Associate Lecturer with the Open University, teaching on the Understanding Health course. Before working for the OU I lectured in physiology and nutrition at The London Institute. I have a background in medical research and gained my biochemistry Ph.D whilst working at the Imperial College School of Medicine.

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