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Health Benefits of Garlic

What Should I Know About It?

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Updated March 24, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Health Benefits of Garlic
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Garlic (Allium sativum) is a plant closely related to onions, leeks, and chives. Extracts of the bulb and clove are sometimes used medicinally.

Health Benefits of Garlic

Research suggests that garlic may help fight the following health problems:

1) High Cholesterol

A number of studies have shown that regular intake of garlic may lead to moderate changes in cholesterol levels. In a 2009 review that analyzed the results of 29 clinical trials, for instance, researchers found that garlic appears to reduce total cholesterol to a modest extent. A study published in 2000, however, indicates that although garlic is superior to a placebo in lowering total cholesterol levels, the use of garlic as a principal treatment of high cholesterol is of "questionable value."

See Natural Remedies for High Cholesterol.

2) High Blood Pressure

Garlic preparations are more effective than a placebo when it comes to reducing blood pressure in people with hypertension, according to a 2008 review and analysis of 25 studies. However, another review (published in 2009) concluded that garlic should not be recommended as a blood pressure-lowering remedy for hypertensive patients.

Find out about remedies for high blood pressure.

3) Colds

Garlic may help fend off colds, suggests a 2001 study. For 12 weeks during cold season, 146 volunteers took either a daily garlic supplement or a placebo. By the end of the study period, 24 colds were reported in the garlic group, compared to 65 in the placebo group.

Learn about cold remedies.

4) Colorectal and Stomach Cancer

In a 2001 review of 19 studies on garlic consumption and cancer incidence, researchers found that regular intake of garlic (in raw, cooked, or supplement form) may help prevent stomach and colorectal cancers.

Common Healing Uses for Garlic

In herbal medicine, garlic is typically used to treat or prevent these conditions:

Is Garlic Safe?

While garlic is generally considered safe, possible adverse effects include:

  • Upset stomach
  • Headache
  • Fatigue
  • Diarrhea

Garlic supplements inhibit platelet aggregation and enhance fibrinolytic activity, so they can increase the risk of bleeding. Multiple cases of bleeding have been associated with the use of garlic.

Caution is advised in people with bleeding disorders and those taking drugs or supplements that may increase the risk of bleeding such as Coumadin (warfarin), Trental (pentoxiflline), aspirin, ginkgo biloba, or vitamin E.  Garlic may also interact with a number of medications, including insulin, immunosuppressive agents, and protease inhibitors.

It is usually recommended that people taking garlic stop in the weeks before and after any type of surgery.

While garlic is likely safe in normal amounts in food, pregnant women should avoid garlic supplements due to a possible increased risk of bleeding or uterine stimulation.

Using Garlic for Health:

Garlic supplements (as well as topically applied garlic oils, often used in treatment of ear infections) are sold in many health food stores and drugstores. Eating chopped or crushed raw garlic may also offer medicinal benefits.

Sources:

Fleischauer AT, Arab L. "Garlic and cancer: a critical review of the epidemiologic literature." J Nutr. 2001 131(3s):1032S-40S.

Josling P. "Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey." Adv Ther. 2001 18(4):189-93.

Reinhart KM, Talati R, White CM, Coleman CI. "The impact of garlic on lipid parameters: a systematic review and meta-analysis." Nutr Res Rev. 2009 22(1):39-48.

Ried K, Frank OR, Stocks NP, Fakler P, Sullivan T. "Effect of garlic on blood pressure: a systematic review and meta-analysis." BMC Cardiovasc Disord. 2008 16;8:13.

Stevinson C, Pittler MH, Ernst E. "Garlic for treating hypercholesterolemia. A meta-analysis of randomized clinical trials." Ann Intern Med. 2000 19;133(6):420-9.

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