Botanical name: Allium sativum
© Steven Foster
Parts used and where grown
Garlic has been used since time immemorial as a culinary spice and medicinal herb. Garlic has been cultivated in the Middle East for more than 5,000 years and has been an important part of Traditional Chinese Medicine. The region with the largest commercial garlic production is central California. China is also a supplier of commercial garlic. The bulb is used medicinally.
Garlic has been used in connection with the following conditions (refer to the individual health concern for complete information):
|Science Ratings||Health Concerns|
Warts (topical application)
BPH (Kastamonu Garlic)
Colon cancer (reduces risk of stomach, esophageal, and colon cancers)
| Reliable and relatively consistent scientific data showing a substantial health benefit. |
Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.
Historical or traditional use (may or may not be supported by scientific studies)
Garlic is mentioned in the Bible and the Talmud. Hippocrates, Galen, Pliny the Elder, and Dioscorides all mention the use of garlic for many conditions, including parasites, respiratory problems, poor digestion, and low energy. Its use in China was first mentioned in A.D. 510. Louis Pasteur studied the antibacterial action of garlic in 1858.
The sulfur compound allicin, produced by crushing or chewing fresh garlic or by taking powdered garlic products with allicin potential, in turn produces other sulfur compounds: ajoene, allyl sulfides, and vinyldithiins.1 Aged garlic products lack allicin, but may have activity due to the presence of S-allylcysteine.
Many publications have shown that garlic supports the cardiovascular system. While earlier trials suggest it may mildly lower cholesterol and triglyceride levels in the blood,2 3 4 more recent trials found garlic to have minimal success in lowering cholesterol and triglycerides.5 6 7 Garlic also inhibits platelet stickiness (aggregation) and increases fibrinolysis,8 which results in a slowing of blood coagulation. It is mildly antihypertensive9 and has antioxidant activity.10
Garlic’s cardiovascular protective effects were illustrated in a four-year clinical trial on people 50–80 years old with atherosclerosis.11 It was found that consumption of 900 mg of a standardized garlic supplement reduced arterial plaque formation by 5–18%. The benefits were most notable in women.
In test tube studies garlic has been found to have antibacterial, antiviral, and antifungal activity.12 However, these actions are less clear in humans and do not suggest that garlic is a substitute for antibiotics or antifungal medications.
Human population studies suggest that eating garlic regularly reduces the risk of esophageal, stomach, and colon cancer.13 14 This may be partly due to garlic’s ability to reduce the formation of carcinogenic compounds.
How much is usually taken?
People who wish to consume garlic and have no aversion to its odor can chew from one to two whole cloves of raw garlic daily. For those who prefer it with less odor, enteric-coated tablets or capsules with approximately 1.3% allin are available. Clinical trials have used 600–900 mg (delivering approximately 5,000–6,000 mcg of allicin potential) per day in two or three divided amounts.15 16 Aged-garlic extracts have been studied in amounts ranging from 2.4–7.2 grams per day.
Are there any side effects or interactions?
Many people enjoy eating garlic. However, some people who are sensitive to it may experience heartburn and flatulence. Because of garlic’s anti-clotting properties, people taking anticoagulant drugs should check with their doctor before taking garlic.17 Those scheduled for surgery should inform their surgeon if they are taking garlic supplements. Garlic appears to be safe during pregnancy and breast-feeding. In fact, two studies have shown that babies like breast milk better from mothers who eat garlic.18 19
Are there any drug interactions?
Certain medicines may interact with garlic. Refer to drug interactions for a list of those medicines.