What Is It?
Health Benefits
Dosage Information
Guidelines for Use
General Interaction
Possible Side Effects
Evidence Based Rating Scale


What Is It?

Along with its well-earned reputation for discouraging friends and repelling potential lovers, this powerful Herb has a storied culinary and medical history. Egyptian pyramid builders took it for strength and endurance. Medieval healers recommended it as protection against supernatural forces--vampires in particular. The French scientist Louis Pasteur investigated its antibacterial properties, and doctors in the two World Wars treated battle wounds with garlic juice when other drugs were unavailable. Most recently, garlic has been touted for heart health as well.

A member of the family that also includes onions and scallions, garlic (Allium sativum) imparts a distinctive flavor and aroma when used in cooking. Its healing powers are concentrated in the most odiferous part of the plant and the one that is also used in the kitchen--the bulb.(1,2)

Health Benefits

When the raw garlic bulb is crushed or chewed, one of its more than 100 therapeutic sulfur compounds--alliin--is converted into allicin, the chemical largely held responsible for garlic's odor and healing powers. (2,3) The same conversion from alliin to allicin can occur with supplements specifically designed to dissolve in the small intestine.

Garlic's healing powers are broad and varied. Researchers are excited about the prospect that garlic may help to protect against certain cancers, for example. That's because it contains cancer-fighting chemicals called allyl sulfides.(4) In addition, animal studies indicate antioxidant properties in allicin may inactivate cell-damaging free radicals and assist the immune system in destroying early cancer cells.(5,6) Specifically, studies in humans have found that garlic is potentially beneficial in preventing digestive cancers such as colon cancer. Animal studies indicate garlic may be beneficial in preventing liver cancer. (7,8) However, there is limited evidence for the prevention of prostate cancer and no credible evidence to suggest garlic prevents breast cancer: more studies are needed. (9)

Specifically, garlic may help to:

  • Keep the heart healthy. Garlic benefits the heart in numerous ways. By making blood platelets less likely to clump and stick to artery walls, it lessens the risk of atherosclerosis (hardening of the arteries) and a subsequent heart attack. The latest findings indicate that the clot-busting compound ajoene, a derivative of allicin, discourages the development of artery-hardening plaque. (10-12) However, evidence that garlic improves serum cholesterol levels has been inconsistent. A recent meta-analysis concluded garlic  does not significantly lower LDL ("bad") cholesterol and triglyceride levels nor raise HDL ("good") cholesterol levels.(13)

    In addition, garlic may promote heart health by maintaining the flexibility of the aorta, the major artery that carries blood from the heart to the rest of the body and one that tends to stiffen with age. In a small, placebo
    -controlled study involving 50-80 year olds, those who took garlic for at least two years ended up with much more flexible aortas than those who were given a placebo. In addition, a 2008 meta-analysis concluded garlic may lower systolic blood pressure (SBP) in patients with elevated SBP though not in patients with normal SBP. (14-16)

  • Fight colds, flu, bronchitis, sore throat, earache, and other types of infections. Garlic's antiseptic and antibacterial abilities were actually recognized centuries ago. Modern research confirms that, at least in the laboratory, the herb fights the germs responsible for causing the common cold, flu, sore throat, sinusitis, and bronchitis. Findings indicate that one of garlic's therapeutic constituents, allicin, blocks key enzymes that aid bacteria and viruses in their effort to invade and damage tissues.(17,18)

  • Treat vaginal yeast infections. Garlic Extract reportedly counters Candida albicans: when given the chance to proliferate, this naturally present organism is responsible for causing most yeast infections. Research suggests that the genital itching, inflammation, and thick discharge associated with vaginal yeast infections may abate with garlic treatment. (19-22)

  • Control athlete's foot, swimmer's ear (otomycosis), and other fungal skin infections. Laboratory studies indicate that compounds in garlic--probably allicin or closely related chemicals--can inhibit unwanted fungi. In a study of 34 Venezuelan soldiers with tinea pedis (athlete’s foot), 100% were cured after applying a topical ajoene cream twice a day for two weeks. (27) It's unclear whether taking garlic orally will fight these types of infections, but garlic oil applied directly to the area is worth a try.(23,24)

Note: Garlic has also been found to be useful for a number of other disorders. For information on these additional ailments, see our Dosage Recommendations Chart for Garlic.


  • tablet
  • softgel
  • powder
  • oil
  • liquid
  • fresh herb
  • capsule
  • dried powdered bulb

Dosage Information

Special tip: When purchasing pills, look for those that supply 10 mg of alliin, with a total allicin potential of 4,000 mcg; this is approximately the same amount found in one clove of fresh garlic.

  • For general health: take 400 to 600 mg of garlic once a day.

  • For colds, sore throat, and flu: take 400 to 600 mg of garlic four times a day until symptoms clear up.

  • For high cholesterol, high blood pressure, and heart disease prevention: take 400 to 600 mg of garlic once or twice a day.

    Be sure to check out our Dosage Recommendations Chart for Garlic, which lists therapeutic dosages for specific ailments at a glance.

  • Guidelines for Use

  • It's a good idea to take garlic with food to buffer its strong odor and aftertaste.

  • Because heating garlic can destroy many of its therapeutic compounds, it's best to rely on supplements when treating a specific disorder. Studies indicate, however, that letting crushed raw garlic rest for 10 minutes before heating does increase levels of allicin and other beneficial compounds.

  • Many experts contend that supplements made from pure garlic powder are the most effective.

  • So-called "deodorized capsules" may effectively remove odor, but manufacturing processes may deplete the garlic's therapeutic effects.

  • In fact, if strong "garlic" breath normally discourages you from taking this herb, try enteric-coated supplements. By passing undigested through the stomach and into the intestines, these pills dramatically reduce the risk for bad breath. They also promote full absorption of the allicin.

  • Garlic supplements can be taken indefinitely.

  • General Interaction

  • Because medicinal amounts of garlic may intensify the effects of medications designed to prevent blood clots (anticoagulants or aspirin) or to reduce high blood pressure (antihypertensives), consult your doctor before combining garlic and these drugs.

  • Garlic may interfere with the action of drugs that lower blood sugar; consult your doctor before taking both at the same time.

    Note: For information on interactions with specific generic drugs, see our WholeHealthMD Drug/Nutrient Interactions Chart.

  • Possible Side Effects

    • Some people have trouble digesting garlic, which can irritate the stomach lining and cause nausea or intestinal gas. Large doses in particular can cause heartburn and diarrhea.

    • Large quantities of garlic can cause body odor and bad breath. This is particularly problematic for people who lack the liver processing system for detoxifying allicin. (2)

    • Contact dermatitis can occur with prolonged handling (28), and chemical burns may result from garlic poultices.(29)


  • Stop garlic supplements at least one week before surgery because the herb's anti-clotting actions may prolong bleeding from a surgical wound.

  • If you plan to take garlic for cholesterol problems, have your doctor check your cholesterol levels after three months to see if they have changed; if they haven't, talk with your doctor about other options.

  • Avoid taking garlic supplements or consuming medicinal amounts of garlic during pregnancy; although no problems have been reported, lab tests suggest that irregular uterine contractions may develop.
  • References

    1. Rivlin Richard S. Historical Perspective on the Use of Garlic. Journal of Nutrition. 2001;131:951S-954S.
    2. Amagase H, Petesch BL, Matsuura H, Kasuga S, Itakura Y. Intake of garlic and its bioactive components. J Nutr. 2001 Mar;131(3s):955S-62S.
    3. Macpherson LJ, Geierstanger BH, Viswanath V, Bandell M, Eid SR, Hwang S, Patapoutian A.The pungency of garlic: activation of TRPA1 and TRPV1 in response to allicin.Curr Biol. 2005 May 24;15(10):929-34.
    4.Thomson M, Ali M. Garlic [Allium sativum]: a review of its potential use as an anti-cancer agent. Curr Cancer Drug Targets. 2003 Feb;3(1):67-81.
    5. Okada Y, Tanaka K, Fujita I, Sato E, Okajima H. Antioxidant activity of thiosulfinates derived from garlic. Redox Rep. 2005;10(2):96-102.
    6. Patya M, Zahalka MA, Vanichkin A, Rabinkov A, Miron T, Mirelman D, Wilchek M, Lander HM, Novogrodsky A. Allicin stimulates lymphocytes and elicits an antitumor effect: a possible role of p21ras. Int Immunol. 2004 Feb;16(2):275-81.
    7. Ngo SN, Williams DB, Cobiac L, Head RJ. Does garlic reduce risk of colorectal cancer? A systematic review. J Nutr. 2007 Oct;137(10):2264-9.
    8. Sundaresan S, Subramanian P. Prevention of N-nitrosodiethylamine-induced hepatocarcinogenesis by S-allylcysteine. Mol Cell Biochem. 2008 Mar;310(1-2):209-14.
    9. Kim JY, Kwon O. Garlic intake and cancer risk: an analysis using the Food and Drug Administration's evidence-based review system for the scientific evaluation of health claims. Am J Clin Nutr. 2009 Jan; 89 (1):257-64.
    10. Hiyasat B, Sabha D, Grötzinger K, Kempfert J, Rauwald JW, Mohr FW, Dhein S. Antiplatelet Activity of Allium ursinum and Allium sativum. Pharmacology. 2009 Jan 28;83(4):197-204.
    11. Dirsch VM, Kiemer AK, Wagner H, Vollmar AM. Effect of allicin and ajoene, two compounds of garlic, on inducible nitric oxide synthase. Atherosclerosis. 1998 Aug;139(2):333-9.
    12. Ledezma E, Apitz-Castro R. Ajoene the main active compound of garlic (Allium sativum): a new antifungal agent. Rev Iberoam Micol. 2006 Jun;23(2):75-80.
    13. Khoo YS, Aziz Z. Garlic supplementation and serum cholesterol: a meta-analysis. J Clin Pharm Ther. 2009 Apr;34(2):133-45.
    14. Breithaupt-Grögler K, Ling M, Boudoulas H, Belz GG. Protective effect of chronic garlic intake on elastic properties of aorta in the elderly. Circulation. 1997 Oct 21;96(8):2649-55.
    15. Reinhart KM, Coleman CI, Teevan C, Vachhani P, White CM. Effects of garlic on blood pressure in patients with and without systolic hypertension: a meta-analysis. Ann Pharmacother. 2008 Dec;42(12):1766-71.
    16. Silagy C, Neil A. A meta-analysis of the effect of garlic on blood pressure. J Hypertension. 1994; 12:463-468.
    17. Abdullah T. A strategic call to utilize Echinacea-garlic in flu-cold seasons. J Natl Med Assoc. 2000 Jan;92(1):48-51.
    18. Josling P. Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey.Adv Ther. 2001;18:189-93.
    19. Moore GS, Atkins RD. The fungicidal and fungistatic effects of an aqueous garlic extract on medically important yeast-like fungi. Mycologia. 1977;69:341-348.
    20. Sandhu DK, Warraich MK, Singh S. Sensitivity of yeasts isolated from cases of vaginitis to aqueous extracts of garlic. Mykosen. 1980;23:691-698.
    21. Prasad G, Sharma VD. Efficacy of garlic (Allium sativum) treatment against experimental candidiasis in chicks. Br Vet J. 1980;136:448-451.
    22. Chung I, Kwon SH, Shim ST, Kyung KH. Synergistic antiyeast activity of garlic oil and allyl alcohol derived from alliin in garlic. J Food Sci. 2007 Nov;72(9):M437-40.
    23. Ledezma E, Marcano K, Jorquera A, De Sousa L, Padilla M, Pulgar M, Apitz-Castro R. Efficacy of ajoene in the treatment of tinea pedis: a double-blind and comparative study with terbinafine. J Am Acad Dermatol. 2000 Nov;43(5 Pt 1):829-32.
    24. Pai ST
    , Platt MW. Antifungal effects of Allium sativum (garlic) extract against the Aspergillus species involved in otomycosis. Lett Appl Microbiol. 1995 Jan;20(1):14-8.
    25. Josling P. Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey. Adv Ther. 2001 Jul-Aug;18(4):189-93.
    26. 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 Jul;155(7):796-9.
    27. Ledezma E, DeSousa L, Jorquera A, et al.
    Efficacy of ajoene, an organosulphur derived from garlic, in the short-term therapy of tinea pedis. Micoses 1996;39:393-395.
    28. Burden AD, Wilkinson SM, Beck MH et al.
    Garlic-induced systemic contact dermatitis. Contact Dermatitis 1994;30:299-315.
    29. Garty BZ. Garlic burns. Pediatrics 1993;91:658-659.

    Evidence Based Rating Scale  

    The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.







    Athlete's Foot







    Numerous studies indicate anti-fungal properties of garlic. (23)  





    Candida Overgrowth Syndrome




    Date Published: 04/18/2005
    Previous  |  Next
    > Printer-friendly Version Return to Top

    © 2000- 2019 ., LLC. 21251 Ridgetop Circle, Suite 150, Sterling, VA 20166. All rights reserved. Reproduction in whole or in part without permission is prohibited. Privacy Policy

    Disclaimer: All material provided in the WholeHealthMD website is provided for educational purposes only. Consult your physician regarding the applicability of any information provided in the WholeHealthMD website to your symptoms or medical condition.