Garlic 

This fact sheet provides basic information about garlic—uses, potential side 

effects, and resources for more information. Garlic is the edible bulb from a 

plant in the lily family. It has been used as both a medicine and a spice for 

thousands of years. 

Common Name—garlic 

Latin Name—Allium sativum 

What It Is Used For 

•	 Garlic’s most common uses as a dietary supplement are for high cholesterol, 

heart disease, and high blood pressure. 

•	 Garlic is also used to prevent certain types of cancer, including stomach and 

colon cancers. 

How It Is Used 

Garlic cloves can be eaten raw or cooked. They may also be dried or powdered 

and used in tablets and capsules. Raw garlic cloves can be used to make oils and 

liquid extracts. 

What the Science Says 

•	 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 studies suggest consuming garlic as a regular part of the diet may 

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. 

•	 Recent NCCAM-funded research includes studies on how garlic interacts 

with certain drugs and how it can thin the blood. 

Side Effects and Cautions 

•	 Garlic appears to be safe for most adults. 

•	 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. This will help ensure 

coordinated and safe care. 

Sources 

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 http://www.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. Agency for Healthcare Research and Quality Web site. Accessed at 

http://www.ahrq.gov/clinic/epcsums/garlicsum.htm on July 9, 2007. 

Garlic. Natural Medicines Comprehensive Database Web site. Accessed at http://www.naturaldatabase.com on July 3, 2007. 

Garlic (Allium sativum L.). Natural Standard Database Web site. Accessed at http://www.naturalstandard.com on 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 

Visit the NCCAM Web site at nccam.nih.gov and view: 

•	 What’s in the Bottle? An Introduction to Dietary Supplements at nccam.nih.gov/health/bottle/ 

•	 Herbal Supplements: Consider Safety, Too at nccam.nih.gov/health/supplement-safety/

NCCAM Clearinghouse 

Toll-free in the U.S.: 1-888-644-6226 

TTY (for deaf and hard-of-hearing callers): 1-866-464-3615 

E-mail: info@nccam.nih.gov

CAM on PubMed 

Web site: nccam.nih.gov/camonpubmed/

NIH Office of Dietary Supplements 

Web site: www.ods.od.nih.gov 

NIH National Library of Medicine’s MedlinePlus 

Garlic Listing: www.nlm.nih.gov/medlineplus/druginfo/natural/patient-garlic.html

This publication is not copyrighted and is in the public domain. Duplication is encouraged. 

NCCAM has provided this material for your information. It is not intended to substitute for the medical 

expertise and advice of your primary health care provider. We encourage you to discuss any decisions 

about treatment or care with your health care provider. The mention of any product, service, or therapy 

is not an endorsement by NCCAM. 

National Institutes of Health 

♦♦♦

U.S. Department of Health and Human Services 

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Created May 2006 

Updated March 2008 

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