Latin Name -Allium sativum
Garlic is the edible bulb from a plant in the lily family. It has been used as a spice and an herbal remedy for thousands of years. Garlic cloves are an important ingredient in cooking around the world, from Italy and France to China and Korea. Garlic cloves may also be dried or powdered and are used in tablets and capsules. Raw garlic cloves are used to make oils and liquid extracts.
Garlic is used as an herbal remedy in the hope of improving problems such as high cholesterol and high blood pressure.
According to research, some evidence indicates that taking garlic can slightly lower blood cholesterol levels; studies have shown positive effects for short-term (1 to 3 months) use. However, an NCCAM-funded study on the safety and effectiveness of three garlic preparations (fresh garlic, dried powdered garlic tablets, and aged garlic extract tablets) for lowering blood cholesterol levels found no effect.
Preliminary research suggests that taking garlic may slow the development of atherosclerosis (hardening of the arteries), a condition that can lead to heart disease or stroke.
Evidence is mixed on whether taking garlic can slightly lower blood pressure.
Some research studies suggest consuming garlic as a regular part of the diet may help lower the risk of certain cancers. However, no clinical trials have examined this. A clinical trial on the long-term use of garlic supplements to prevent stomach cancer found no effect.
Side Effects and Cautions Summary
- Garlic side effects include breath and body odor, heartburn, upset stomach, and allergic reactions. These side effects are more common with raw garlic.
- Garlic can thin the blood (reduce the ability of blood to clot) in a manner similar to aspirin. This effect may be a problem during or after surgery. Use garlic with caution if you are planning to have surgery or dental work, or if you have a bleeding disorder. A cautious approach is to avoid garlic in your diet or as a supplement for at least 1 week before surgery.
- Garlic has been found to interfere with the effectiveness of saquinavir, a drug used to treat HIV infection. Its effect on other drugs has not been well studied.
- Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health to help ensure coordinated and safe care. Complementary or alternative therapy should not be used in place of conventional medical care or to delay seeking that care.
- Gardner CD, Lawson LD, Block E, et al. Effect of raw garlic vs. commercial garlic supplements on plasma lipid concentrations in adults with moderate hypercholesterolemia: a randomized clinical trial. Archives of Internal Medicine. 2007;167(4):346–353.
- National Cancer Institute. Garlic and Cancer Prevention: Questions and Answers. National Cancer Institute Web site. Accessed at cancer.gov/newscenter/pressreleases/garlic on July 9, 2007.
- Agency for Healthcare Research and Quality. Garlic: Effects on Cardiovascular Risks and Disease, Protective Effects Against Cancer, and Clinical Adverse Effects. Accessed at ahrq.gov/clinic/epcsums/garlicsum.htm on July 9, 2007.
- Garlic. Natural Medicines Comprehensive Database Web site. Accessed July 3, 2007.
- Garlic (Allium sativum L.). Natural Standard Database Web site. Accessed June 28, 2007.
- Garlic. In: Blumenthal M, Goldberg A, Brinckman J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Lippincott Williams & Wilkins; 2000:139–148.
- Milner JA. Garlic (Allium sativum). In: Coates P, Blackman M, Cragg G, et al., eds. Encyclopedia of Dietary Supplements. New York: NY: Marcel Dekker; 2005:229–240.
For More Information
The National Center for Complementary and Alternative Medicine (NCCAM) Clearinghouse
The NCCAM Clearinghouse provides information on CAM and NCCAM, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.
NIH Office of Dietary Supplements
Web site: ods.od.nih.gov
NIH National Library of Medicine’s MedlinePlus
Garlic Listing: www.nlm.nih.gov/medlineplus/druginfo/natural/patient-garlic.html
Source: National Center for Complementary and Alternative Medicine, Garlic fact sheet, Created May 2006, Updated March 2008