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Garlic

Also listed as: Allium sativum

Overview
Plant Description
What's It Made Of?
Available Forms
 
How to Take It
Precautions
Possible Interactions
Supporting Research

Overview

Garlic has been used as both food and medicine in many cultures for thousands of years, dating back to when the Egyptian pyramids were built. In early 18th-century France, gravediggers drank crushed garlic in wine believing it would protect them from the plague that killed many people in Europe. During both World Wars I and II, soldiers were given garlic to prevent gangrene. Today garlic is used to help prevent heart disease, including atherosclerosis or hardening of the arteries (plaque buildup in the arteries that can block the flow of blood and may lead to heart attack or stroke), high cholesterol, high blood pressure, and to boost the immune system. Garlic may also help protect against cancer.

Garlic is rich in antioxidants, which help destroy free radicals -- particles that can damage cell membranes and DNA, and may contribute to the aging process as well as the development of a number of conditions, including heart disease and cancer. Antioxidants neutralize free radicals and may reduce or even help prevent some of the damage they cause over time.

The conditions for which garlic is showing the most promise include:

Heart disease

Some evidence suggests that garlic may help prevent heart disease. It may slow down atherosclerosis (hardening of the arteries) and lower blood pressure slightly, between 7% and 8%. Most of the studies on high blood pressure have used a specific formulation called Kwai. One study that lasted 4 years found that people who took 900 mg daily of standardized garlic powder slowed the development of atherosclerosis. Garlic also seems to be an anticoagulant, meaning it acts as a blood-thinner, which may help prevent heart attacks and strokes.

Earlier studies found that garlic lowered high cholesterol, but more recent studies that are high quality have found no effect.

Common cold

Some early evidence suggests garlic may help prevent colds. In one study, people took either garlic supplements or placebo for 12 weeks during "cold season" between November and February. Those who took garlic had fewer colds than those who took placebo. Plus, when they did get a cold, the people taking garlic saw their symptoms go away faster than those who took placebo.

Cancer

Garlic may strengthen the immune system, helping the body fight diseases such as cancer. In test tubes, garlic seems to have anti-cancer activity. And population studies -- ones that follow groups of people over time -- suggest that people who eat more raw or cooked garlic are less likely to develop certain types of cancer, particularly colon and stomach cancers. In fact, researchers who reviewed 7 studies found a 30% reduction in risk of colorectal cancer among people who ate a lot of raw or cooked garlic. Garlic supplements don’t seem to have the same effect.

  • A large-scale study, called the Iowa Women's Health Study, looked at how much garlic, fruit, and vegetables were in the diets of 41,000 middle-aged women. Results showed that women who regularly ate garlic, fruits, and vegetables had a 35% lower risk of developing colon cancer.
  • Garlic may help the immune system function better during times of need such as in cancer. In a study of 50 people with inoperable colorectal, liver, or pancreatic cancer, immune activity improved after they took aged garlic extract for 6 months.

Other uses

  • In test tubes, garlic kills roundworms, Ascaris lumbricoides, which is the most common type of intestinal parasite. But it hasn’t been tested in humans, so researchers don’t know if it works in people.
  • Several studies report that a garlic gel, applied to the skin, may treat ringworm, jock itch, and athlete’s foot.

Plant Description

Garlic is a perennial that originally came from central Asia, and is now grown throughout the world. It can grow 2 feet high or more. The part of this plant used for medicine is the compound bulb. Each bulb is made up of 4 - 20 cloves, and each clove weighs about 1 gram. Garlic supplements can either be made from fresh, dried, aged, or garlic oil, and each may have different effects on the body.

What's It Made Of?

Researchers once thought that a chemical called allicin was responsible for garlic’s benefits, as well as its distinctive smell. But there are other chemicals in garlic, including some sulfur-containing compounds, that may help lower cholesterol, fight heart disease, and help prevent come cancers.

Available Forms

Garlic supplements are made from whole fresh garlic, dried, or freeze-dried garlic, garlic oil, and aged garlic extracts.

Not all garlic contains the same amount of active ingredients. It is important to read the label on all garlic products carefully. To get the most benefit, use standardized garlic products. Also, follow the directions of a qualified health care provider who is experienced in herbal medicine.

How to Take It

Pediatric

Ask your doctor before giving garlic supplements to a child. Research hasn't yet found what an effective and safe dose might be.

Adult

Whole garlic clove (as a food supplement): 2 - 4 grams per day of fresh, minced garlic clove (each clove is approximately 1 gram)

Aged garlic extract: 600 - 1,200 mg, daily in divided doses

Tablets of freeze-dried garlic: 200 mg, 2 tablets 3 times daily, standardized to 1.3% alliin or 0.6% allicin. Products may also be found standardized to contain 10 - 12 mg/Gm alliin and 4,000 mcg of total allicin potential (TAP).

Fluid extract (1:1 w/v): 4 mL, daily

Tincture (1:5 w/v): 20 mL, daily

Oil: 0.03 - 0.12 mL, 3 times daily

Precautions

The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and that can interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.

Garlic is listed as Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration.

Side effects from garlic include upset stomach, bloating, bad breath, body odor, and a stinging sensation on the skin from handling too much fresh or dried garlic. Handling garlic may also cause skin lesions. Other, more rare side effects that have been reported by those taking garlic supplements include headache, fatigue, loss of appetite, muscle aches, dizziness described as vertigo, and allergies such as an asthmatic reaction or skin rash.

Garlic has blood-thinning properties. Too much garlic can increase your risk for bleeding during or after surgery. It may also interact with blood-thinning medications (see "Interactions").

People with ulcers or thyroid problems should ask their doctor before taking garlic.

Possible Interactions

Garlic may alter the function of certain prescription medications. If you are being treated with any of the following medications, you should not use garlic supplements without first talking to your health care provider.

Isoniazid(Nydrazid) -- This medication is used to treat tuberculosis. Garlic may lower the amount of this medication that the body absorbs, making it less effective.

Birth controlpills -- Garlic may make birth control pills less effective.

Blood-thinning medications -- Garlic may make the actions of these medications stronger, increasing the risk of bleeding. Blood-thinners include warfarin (Coumadin), clopidogrel (Plavix), and aspirin.

Medications for HIV/AIDS -- Garlic may lower blood levels of protease inhibitors, medications used to treat people with HIV. Protease inhibitors include:

  • Amprenavir (Agenerase)
  • Fosamprenavir (Lexiva)
  • Indinavir (Crixivan)
  • Nelfinavir (Viracept)
  • Ritonavir (Norvir)
  • Saquinavir (Fortovase)

Nonsteroidal anti-inflammatory drugs (NSAIDs) -- Both NSAIDs and garlic may increase the risk of bleeding. NSAIDs include ibuprofen (Advil, Motrin) and naproxen (Aleve) as well as prescription medications.

Supporting Research

Ackermann RT, Mulrow CD, Ramirez G, Gardner CD, Morbidoni L, Lawrence VA. Garlic shows promise for improving some cardiovascular risk factors. Arch Intern Med. 2001;161:813-824.

Alder R, Lookinland S, Berry JA, et al. A systematic review of the effectiveness of garlic as an anti-hyperlipidemic agent. J Am Acad Nurse Pract. 2003;15(3):120-129.

Ang-Lee MK, Moss J, Yuan C-S. Herbal medicines and perioperative care [review]. JAMA. 2001;286(2):208-216.

Ashraf R, Aamir K, Shaikh AR, Ahmed T. Effects of garlic on dyslipidemia in patients with type 2 diabetes mellitus. J Ayub Med Coll Abbottabad. 2005;17(3):60-4.

Bailey C, Day C. Traditional plants medicine as treatments for diabetes. Diabetes Care. 1989;12:553-564.

Berthold HK, Sudhop T. Galic preparation for prevention of atherosclerosis. Curr Opin Lipidol. 1998;9(6):565-569.

Berthold HK, Sudhop T, von Bergmann K. Effect of a garlic oil preparation on serum lipoproteins and cholesterol metabolism. JAMA. 1998;279.

Borrelli F, Capasso R, Izzo AA. Garlic (Allium sativum L.): adverse effects and drug interactions in humans. Mol Nutr Food Res. 2007;51(11):1386-97.

Caron MF, White CM. Evaluation of the antihyperlipidemic properties of dietary supplements. Pharmacotherapy. 2001;21(4):481-487.

Delaha EC, Garagusi VF. Inhibition of mycobacteria by garlic extract (Alliumsativum). Antimicrob Agents Chemother. 1985;27(4):485-486.

Dillon SA, Burmi RS, Lowe GM, et al. Antioxidant properties of aged garlic extract: an in vitro study incorporating human low density lipoprotein. Life Sci. 2003;72(14):1583-1594.

Dorant E, van den Brandt PA, Goldbohm RA. A prospective cohort study on the relationship between onion and leek consumption, garlic supplement use and the risk of colorectal carcinoma in The Netherlands. Carcinogenesis. 1996;17(3):477-484.

Dorant E, van den Brandt PA, Goldbohm RA. Allium vegetable consumption, garlic supplement intake, and female breast carcinoma incidence. Breast Cancer Res Treat. 1995;33(2):163-170.

Dorant E, van den Brandt PA, Goldbohm RA, Hermus RJ, Sturmans F. Garlic and its significance for the prevention of caner in humans: a critical view. Br J Cancer. 1993;67(3):424-429.

Fleischauer AT, Arab L. Garlic and cancer: a critical review of the epidemiologic literature. J Nutr. 2001;131:1032S-1040S.

Fleischauer AT, Poole C, Arab L. Garlic consumption and cancer prevention: meta-analyses of colorectal and stomach cancers. Am J Clin Nutr. 2000;72:1047-1052.

Fugh-Berman A. Herb-drug interactions [review]. Lancet. 2000;355:134-138.

Fugh-Berman A. Herbs and dietary supplements in the prevention and treatment of cardiovascular disease. Prev Cardiol. 2000;3:24-32.

Garlic supplements can impede HIV medication. J Am Coll Surg. 2002;194(2):251.

Gallicano K, Foster B, Choudhri S. Effect of short-term administration of garlic supplements on single-dose ritonavir pharmacokinetics in healthy volunteers. Br J Clin Pharmacol. 2003;55(2):199-202.

Gullett NP, Ruhul Amin AR, Bayraktar S, Pezzuto JM, Shin DM, Khuri FR, Aggarwal BB, Surh YJ, Kucuk O. Cancer prevention with natural compounds. Semin Oncol. 2010 Jun;37(3):258-81. Review.

Hassan ZM, Yaraee R, Zare N, et al. Immunomodulatory affect of R10 fraction of garlic extract on natural killer activity. Int Immunopharmacol. 2003;3(10-11):1483-1489.

Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin. Am J Health Syst Pharm. 2000;57(13):1221-1227.

Heron S, Yarnell E. Treating parasitic infections with botanical medicines. Altern Complement Ther. 1999;8:214-224.

Isaacsohn JL, Moser M, Stein EA, et al. Garlic powder and plasma lipids and lipoproteins: a multicenter, randomized, placebo-controlled trial. Arch Intern Med. 1998;158(11):1189-1194.

Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: a systematic review. Drugs. 2001;61(15):2163-2175.

James JS. Garlic reduces squinavir blood levels 50%; may affect other drugs. AIDS Treat News. 2001;375:2-3.

Josling P. Preventing the common cold with a garlic supplement: a double blind, placebo-controlled survey. Adv Ther. 2001;18(4):189-193.

Kannar D, Wattanapenpaiboon N, Savige GS, Wahlqvist ML. Hypocholesterolemic effect of an enteric coated garlic supplement. J Am Coll Nutr. 2001;20(3):225-231.

Kendler BS. Recent nutritional approaches to the prevention and therapy of cardiovascular disease. Prog Cardiovasc Nurs. 1997;12(3):3-23.

Koscielny J, Klubendorf D, Latza R, Schmitt R, Radtke H, Siegel G, Kiesewetter H. The antiatherosclerotic effect of Allium sativum. Atherosclerosis. 1999;144:237-249.

Levi F, Pasche C, La Vecchia C, Lucchini F, Franceschi S. Food groups and colorectal cancer risk. Br J Cancer. 1999;79(7-8):1283-1287.

Loy MH, Rivlin RS. Garlic and cardiovascular disease. Nutr Clin Care. 2000;3(3):146-151.

Mantle D, Lennard TW, Pickering AT. Therapeutic applications of medicinal plants in the treatment of breast cancer: a review of their pharmacology, efficacy and tolerability. Adverse Drug React Toxicol Rev. 2000;19(3):223-240.

Markowitz JS, Devane CL, Chavin KD, et al. Effects of garlic (Allium sativum L.) supplementation on cytochrome P450 2D6 and 3A4 activity in healthy volunteers. Clin Pharmacol Ther. 2003;74(2):170-177.

Mashour NH, Lin GI, Frishman WH. Herbal medicine for the treatment of cardiovascular disease. Arch Intern Med. 1998;158:2225–2234.

Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions [review]. Arch Intern Med. 1998;158:2200-2211.

Milner JA. A historical perspective on garlic and cancer. J Nutr. 2001;131(3s):1027S-1031S.

Morelli V, Zoorob RJ. Alternative therapies: part I. Depression, diabetes, obesity. Am Fam Physician. 2000;62(5):1051-1060.

Morihara N, Nishihama T, Ushijima M, Ide N, Takeda H, Hayama M. Garlic as an anti-fatigue agent. Mol Nutr Food Res. 2007;51(11):1329-34.

Munday JS, James KA, Fray LM, Kirkwood SW, Thompson KG. Daily supplementation with aged garlic extract, but not raw garlic, protects low density lipoprotein against in vitro oxidation. Atherosclerosis. 1999;143(2):399-404.

Ngo SN, Williams DB, Cobiac L, Head RJ. Does garlic reduce the risk of colorectal cancer? A systematic review. J Nutr. 2007;137(10):2264-9.

Nies LK, Cymbala AA, Kasten SL, et al. Complementary and alternative therapies for the management of dyslipidemia. Ann Pharmacother. 2006;40(11):1984-92.

O'Gara EA, Maslin DJ, Nevill AM, Hill DJ. The effect of simulated gastric environments on the anti-Helibacter activity of garlic oil. J Appl Microbiol. 2008; 104(5):1324-31.

Pinto JT, Rivlin RS. Antiproliferative effects of allium derivatives from garlic. J Nutr. 2001;131(3S):1058S-1060S.

Rahman K. Effects of garlic on platelet biochemistry and physiology. Mol Nutr Food Res. 2007;51(11):1335-44.

Rahman K. Historical perspective on garlic and cardiovascular disease. J Nutr. 2001;131(3s):977S-979S.

Ried K, Frank OR, Stocks NP. Aged garlic extract lowers blood pressure in patients with treated but uncontrolled hypertension: a randomised controlled trial. Maturitas. 2010 Oct;67(2):144-50.

Sarrell EM, Mandelberg A, Cohen HA. Efficacy of naturopathic extracts in the management of ear pain associated with acute otitis media. Arch Pediatr Adolesc Med. 2001;155:796-799.

Salih BA, Abasiyanik FM. Does regular garlic intake affect the prevalence of Helicobacter pylori in asymptomatic subjects? Saudi Med J. 2003;24(8):842-845.

Scharbert G, Kalb ML, Duris M, Marschalek C, Kozek-Langenecker SA. Garlic at dietary doses does not impair platelet function. Anesth Analg. 2007;105(5):1214-8.

Siegers CP, Steffen B, Robke A, Pentz R. The effects of garlic preparations against human tumor cell proliferation. Phytomedicine. 1999;6(1):7-11.

Silagy CA, Neil AW. A meta-analysis of the effect of garlic on blood pressure. J Hypertens. 1994;12:463-468.

Sobenin IA, Pryanishnikov VV, Kunnova LM, Rabinovich YA, Martirosyan DM, Orekhov AN. The effects of time-released garlic powder tablets on multifunctional cardiovascular risk in patients with coronary artery disease. Lipids Health Dis. 2010 Oct 19;9:119.

Spigelski D, Jones PJ. Efficacy of garlic supplementation in lowering serum cholesterol levels. Nutr Rev. 2001;59(7):236-241.

Steiner M, Khan AH, Holbert D, Lin RI. A double-blind crossover study in moderately hypercholesterolemic men that compared the effect of aged garlic extract and placebo administration on blood lipids. Am J Clin Nutr. 1996;64:866–870.

Steinmetz KA, Kushi LH, Bostick RM, Folsom AR, Potter JD. Vegetables, fruit, and colon cancer in the Iowa Women's Health Study. Am J Epidemiol. 1994;139(1):1-15.

Stevinson C, Pittler MH, Ernst E. Garlic for treating hypercholesterolemia. Ann Intern Med. 2000;133(6):420-429.

Superko HR, Krauss RM. Garlic powder, effect on plasma lipids, postprandial lipemia, low-density lipoprotein particle size, high-density lipoprotein subclass distribution and lipoprotein(a). J Am Coll Cardiol. 2000;35(2):321-326.

Wang HX, NG TB. Natural products with hypoglycemic, hypotensive, hypocholesterolemic, antiatherosclerotic and antithrombotic activities. Life Sci. 1999;65(25):2663-2677.

Witte JS, Longnecker MP, Bird CL, Lee ER, Frankl HD, Haile RW. Relation of vegetable, fruit, and grain consumption to colorectal adenomatous polyps. Am J Epidemiol. 1996;144(11):1015-1025.

Yeh YY, Liu L. Cholesterol-lowering effect of garlic extracts and organosulfur compounds: human and animal studies. J Nutr. 2001;131(3s):989S-993S.


Review Date: 1/26/2011
Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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Uses of this Herb
Atherosclerosis
Breast cancer
Bronchitis
Colorectal cancer
Common cold
Cough
Diabetes
Hypercholesterolemia
Hypertension
Intestinal parasites
Myocardial infarction
Otitis media
Prostate cancer
Roundworms
Stroke
Tuberculosis
Drugs that Interact
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