Written by Edzard Ernst and the CAM-Cancer Consortium.
Updated August 14, 2013

Garlic (Allium sativum)

What is it?


Garlic is a bulbous plant of the Allium (onion) family commonly used for culinary purposes. For medicinal purposes fresh or dried parts of the bulb or the oil from the bulb are usually used.

Scientific / common name

Allium sativum L (Alliaceae/Liliaceae) is commonly referred to as garlic. Ajo is also sometimes used.


Alliin, diallyldisulfate, ajoen and others 1. Allicin, considered to be one of the main active ingredients, and other sulfur-containing compounds are formed from alliin enzymatically when garlic is crushed or chopped 1,2. It is considered that 1 mg alliin is equivalent to 0.45 mg allicin 2,3. Commercial garlic preparations are often standardised on the content of sulfur-containing constituents, particularly to alliin, or on the allicin yield 2.

Application and dosage

It is usually taken orally in the following dosages.
Dried bulb: 2- 4g three times daily for upper respiratory tract infections 4-6; 0.5-1.0g daily for the prophylaxis of atherosclerosis 7,8.
Fresh garlic: 4g daily 1-3.
Oil: 0.03-0.12 ml three times daily 2,9.
Juice of garlic (BPC 1949) 2-4 ml 2,10.
Extract: 600-900mg of standardised extract (1.3% alliin content) daily in divided doses 1.


Garlic has been used medicinally in several ancient cultures. Prescribers today are mainly herbalists, naturopaths and doctors. Many consumers self-prescribe garlic supplements. Garlic is a common food and spice. It is offered as “over the counter “ (OTC) preparations (food supplements) in form of single-ingredient or multi-ingredients preparations by many providers (see list in 11).

Claims of efficacy

The Monograph of ESCOP (2003) recommends Allii sativi bulbus for the prophylaxis of atherosclerosis, for the treatment of elevated blood lipid levels insufficiently influenced by diet, for the improvement of the circulation in peripheral arterial vascular disease and for upper respiratory tract infections and catarrhal conditions 7,8.

The WHO-Monograph states uses supported by clinical data as adjuvant to the dietetic management in the treatment of hyperlipidaemia, and in the prevention of atherosclerosis, age dependent vascular changes and mild hypertension 4,8.

Claims of efficacy in the prevention of cancer are mainly based on in vitro and animal studies 2.

Mechanism of action

Garlic's mechanisms of action have been studied extensively. It has antibacterial, antiviral, antifungal, antihypertensive, blood glucose lowering, antithrombotic, antimutagentic and antiplatelet activities 1.

Several pathways have been identified for each of which the evidence is substantial:

  • Modulation of carcinogen metabolism 12
  • Inhibition of cell cycle progression 13
  • Induction of apoptosis 14-19
  • Histone modification 12
  • Inhibition of angiogenesis 12
  • Protection against DNA-damage 20
  • Inhibition of cell proliferation 21-24
  • Modulation of gene expression 21,25
  • Inhibition of tumor cell motility 26
  • Antioxidation 27
  • Modification of drug metabolising enzymes especially the family of the hepatic cytochrome P450 (CYP) enzymes2
  • Immunomodulatory activity 2,28.

Many of the findings from animal studies support these postulated mechanisms 17,22-24,27-30.

Alleged indications

It is claimed that garlic might reduce the cancer risk.

Prevalence of use

Garlic is widely used as a food and spice. Garlic supplements have become very popular in developed countries. Exact prevalence figures are not available.

Legal issues

Garlic preparations are sold in most countries as food supplements.

Cost and expenditure

A one week supply of garlic supplements would cost between €5 and €10.

Citation Edzard Ernst, CAM-Cancer Consortium. Garlic (Allium sativum) [online document]. http://ws.cam-cancer.org/The-Summaries/Herbal-products/Garlic-Allium-sativum. August 14, 2013.


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