It makes food taste great and brings any dish to life with flavour.  I love garlic!  Garlic is a type of vegetable, there are two species: Allium sativum  (cultivated garlic) and Allium ursinum  (wild bear's garlic), both of which belong to the Amaryllis (Amaryllidaceae) family.

A plethora of health benefits are attributed to garlic with studies showing that it seems to have positive effects for the heart and circulatory system, immune system and digestive system.  It also seems to be anti-parasitic, anti-viral, anti-fungal and anti-bacterial.  The lists go on and on!

Today I wanted to look at garlic supplementation in relation to lowering blood pressure.  Until very recently research on garlic supplementation and blood pressure had been inconclusive.  However, the latest, most comprehensive review(1) of scientific evidence “suggests that garlic preparations are superior to placebo in reducing blood pressure in individuals with hypertension [high blood pressure]”.  The review of scientific literature was undertaken by researchers at The University of Adelaide, South Australia.  The scientists looked at studies that were published between 1955 and 2007, and only included ‘high quality’ research (randomised controlled trials with true placebo groups).  A significant association was found between blood pressure at the start of intervention with garlic supplements and the levels of blood pressure reduction.

The garlic was effective at lowering both the systolic and diastolic blood pressure.  Systolic blood pressure, represented by the top number in a blood pressure reading, is the measure of the phase of the heartbeat when the heart contracts and pumps blood into the arteries.  Diastolic blood pressure, represented by the bottom number in a blood pressure reading, is the measure of the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood. 

The review found that, on average, garlic reduced systolic blood pressure by 4.6 mmHg.  The scientists also looked at studies that were conducted with people with a high blood pressure (hypertension), in these studies the garlic had a more pronounced effect with a reduction of systolic blood pressure by an average of 8.4 mmHg and diastolic blood pressure by 7.3 mmHg. The higher a person's blood pressure was at the beginning of the study, the more it was reduced by taking garlic supplements.

These results are very similar to those of widely used hypertension drugs such as beta blockers, which reduce systolic blood pressure by around 5 mmHg, and ACE (angiotensin converting enzyme) inhibitors, which produce around an 8 mmHg drop in systolic blood pressure.

In the population as a whole, the authors of the study note that a reduction of systolic blood pressure by around 4-5 points and diastolic blood pressure by 2-3 points could cut the risk of heart disease and heart disease-related death by up to 20 percent.  The scientists also note that more research is needed to determine whether garlic supplementation might have long-term effects on heart disease risk. 

In most of the studies reviewed in this paper the participants given garlic took it in powdered form as a standardized supplement at a dose of 600 mg - 900 mg daily for 12-23 weeks. The garlic supplements provided around 3.6 mg - 5.4 mg of allicilin which is the active ingredient in garlic.  A fresh clove of garlic contains around 5 mg - 9 mg of allicin (and tastes wonderful!), so whether you eat garlic regularly or choose to take a supplement it may well be helpful for your blood pressure or for your health in general!

As high blood pressure is a (silent but) major risk factor for heart attack I wanted to mention the British Heart Foundation campaign which aims to alert us to the more visible symptoms of a heart attack.  As part of the campaign there will be a two minute TV  promotion at 9.17pm on ITV1 this Sunday (10th August) during a break in the  ‘Midsomer Murders’ programme.  The charity is calling the event ‘Watch Your Own Heart Attack’.  More information can be found on their website or by clicking on this link.

(1)Ried K et al.  2008.  Effect of garlic on blood pressure: A systematic review and meta-analysis.  BMC Cardiovascular Disorder.  8:13(16 June), [E-pub doi:10.1186/1471-2261-8-13]

Written by Ani Kowal