Garlic and Blood Pressure

Garlic, is a perennial herb belonging to liliaceae or lily family, having biological name as allium sativum, is a most famous and important medicinal herb and is cultivated throughout world. Garlic was once native to central Asia but now it is grown in almost all parts of world in concern to its wide therapeutic activity.

The medicinal property of plant is associated with bulb. These bulbs consist of 7-35 cloves that are covered by a papery, transparent white glistening skin. Garlic plant can reach up to height of 2 feet.

Garlic is a legendary folk remedy for treatment of hypertension. Garlic and blood pressure lowering effect are somehow interrelated. Many countries like china, japan, Germany have noticed the beneficial effect of garlic and declared garlic as an official material for treatment of various deaesases.In India garlic is recommended for treatment of heart diseases and rheumatism. In Egypt, labourers who were building pyramids of Cheops in 2800 B.C.E were given a daily clove of garlic in order to provide strength and protection.

Chemical Constituent of Garlic

Garlic is composed of sulphur containing compounds like Allicin, diallyl disulphide, diallyl trisulphide and selenium. The therapeutic and pungent property of garlic is due to presence of allicin.  Allicin is formed from allin when fresh cloves are crushed or cooked, by the action of enzyme allinase. This process is initiated by the effect of heat, oxygen and water. The cooked garlic or “aged garlic” produces neither strong odour nor medicinal effect as compared to fresh ones; this is because allin is predominant in fresh garlic and as more of allin more amount of allicin will be formed. Another component called as ajoene in garlic is an antithrombotic agent and helps in lowering blood vessels.

Mechanism of action of Garlic

Garlic has unique characteristic, it is not limited to treatment of hypertension, instead it is utilised as an ailment to various condition like high cholesterol, cancer, heart problems including atherosclerosis and hardening of arteries, it also boosts up immune system.

Let’s talk about garlic and blood pressure. Researches have shown that by regular intake of garlic results in drop of 7.7 drop in systolic blood pressure and 5 points drop in diastolic blood pressure. Therefore it can be essential component for dietary programmes especially for patient with high blood pressure.

Garlic lowers blood pressure possibly by three mechanisms- by thinning blood, blocking angiotensin II and by effect on adrenal glands. Garlic acts on adrenal system and prevents them from increasing blood pressure.

Garlic is also recognised as natural blood thinner and as anticoagulant. It prevents platelet aggregation by breaking down or preventing the formation of clumps or aggregates which later forms of clots, which may increase risk of heart attack and stroke.  Some researchers suggest that antiplatelet activity is due to the stimulation of nitrogen oxidase synthase (NOS), which produces an important vasodilating agent called nitric oxide.

blood pressure

Angiotensin convertase enzyme is required for the formation of angiotensin II which increases blood pressure. Glutamyl cysteine, a component in garlic, is responsible for natural inhibiting activity towards ACE and thus blocks the formation of angiotensin II. Adenosine in garlic helps in dilation of blood vessels. However, these effects are pronounced by the presence hydrogen sulphide and allicin in garlic which acts by inhibiting angiotensin II and dilation of blood vessels.

Garlic acts as mild diuretic, thus it promotes excretion of excessive salts via kidney and finally lowers blood pressure. garlic also have antibacterial activity, antiviral and antifungal activity, sometimes blood pressure rises due to presence of excess intestinal microbes or by toxic chemicals released by such microbes. The antibacterial activity of garlic might help in destroying such microbes; however antibiotic activity of garlic is not as potent as penicillin.

Garlic doesn’t have any effect on normal blood pressure. It either effects on high or low blood pressure so there’s no harm in consuming garlic in people with normal blood pressure.

Dosage of garlic

Garlic is consumed in variety like as whole fresh cloves of garlic, as dried or freeze dried garlic, garlic oil, tincture or aged garlic extract. Dosage value varies according to the type of preparation.

Whole garlic clove (as a food supplement): It is recommended to have at least 2-4 cloves per day which ranges up to 2-4 grams of garlic.

  • Aged garlic extract: 600-1200 mg, divided into certain doses
  • Freeze dried garlic: 1200 mg split it into 3 doses.
  • Fluid extract (1:1w/v): daily 4 ml
  • Tincture (1.5 w/v): 20ml daily
  • Oil: 0.03-0.12 ml, 3 times daily

Children’s- Always consult doctor before giving garlic supplements to a child as safe and adequate dose for children has not been discovered yet.

Side effects of garlic

We have studied about relation between garlic and blood pressure but garlic produces pungent breathe which is not acceptable by many people and they avoid eating garlic. However, beneficial outcomes of garlic should not be overlooked just because it produces bad breath. Nowadays certain tablets of garlic are available which eradicates the problem of bad breathe.

Other side effects of garlic includes upset stomach, bloating, bad body odour, skin lesions and stinging sensation on the skin from handling too much fresh or dried garlic.


  • Certain medicaments may react with garlic. Thus use of garlic should be avoided before taking following medicaments
  • Blood thinning agents- Garlic should be avoided with agents like warfarin and aspirin because it may make action of such medicaments stronger and increase the risk of bleeding.
  • Birth control pills- Garlic may reduce potency of birth control pills.
  • NSAIDS- Combination of NSAID and garlic may increase risk of bleeding.
  • Medications for HIV/AIDS- Garlic may lower blood levels of protease inhibitors like Amprenavir, Indinavir, and Ritonavir etc.


Garlic is an important medicinal herb but garlic alone itself will not produce expected outcomes. We need to make some lifestyle changes like healthy diet, exercise and quit smoking and alcohol, such actions can prove to be beneficial in lowering blood pressure.