The active component of garlic is a sulfur compound called allicin, which is produced when the garlic clove is broken. Allicin, in turn, becomes ajoene, allyl sulfide, and vinyldithiin.¹

Among garlic’s known benefits are its ability to support the cardiovascular system’s health,² its action as an antioxidant,³ and its antibacterial powers.⁴ Warm garlic oil applied in the ear has been shown effective in treating mild ear infections. Garlic taken regularly is also effective in reducing the risk of stomach and colon cancers.⁵

Contrary to commonly held opinion, garlic’s strong flavor is actually enjoyed by breastfeeding children;⁶ it is not certain, however, how much of garlic’s medicinal power is transmitted via breastmilk.

Natural Sources: Increasing the amount of garlic used in cooking will offer many of the effects of a garlic supplement.

Useful in treatment of:
Atherosclerosis some animalstudies indicate that garlic may slow the progression of atherosclerosis. ^7,8

Garlic may lower High Cholesterol by approximately 10%^9,10

Garlic may lower High blood pressure by 5 to 10% more than placebo in some studies.^11,12

One study showed that women who ingested garlic were 30% less likely to develop Colon Cancer.¹³

Garlic is sometimes used for Athlete’s Foot, ear infections, HIV Support, vaginitis and yeast infection, with less supportive data. It is considered a topical antibiotic, but it is unclear if it posesses any activity when taken internally.

Recommended Dosage: One whole clove daily, or 900 mg garlic (standardized to 1.3% alliin) daily.

Contraindications: Patients with bleeding disorders or who are taking anti-coagulants (warfarin, coumadin, pentoxifylline)should consult with a doctor before using a garlic supplement. Garlic and Ginkgo biloba together may predispose to bleeding in susceptible individuals.Garlic intolerance may result in heartburn or flatulence.

References:
¹Koch HP, Lawson LD, eds., Garlic: The Science and Therapeutic Application of Allium sativaum L and Related Species, 2d ed. Baltimore: Williams and Wilkins, 1996.
^2
3Kleijnen J, Knipschild P, Ter Riet G. Garlic, onion and cardiovascular risk factors: A review of the evidence from human experiments with emphasis on commercially available preparations. Br J Clin Pharmacol 1989;28:535–44.
⁴Hughes BG, Lawson LD. Antimicrobial effects of Allium sativum L. (garlic), Allium ampeloprasum L. (elephant garlic) and Allium cepa L. (onion), garlic compounds and commercial garlic supplement products. Phytother Res 1991;5:154–58.
⁵Dorant E, van der Brandt PA, et al. Garlic and its significance for the prevention of cancer in humans: A critical review. Br J Cancer 1993;67:424–29.
⁶Mennella JA, Beauchamp GK. The effects of repeated exposure to garlic-flavored milk on the nursling’s behavior. Pediatr Res 1993;34:805–8.
⁷Efendi JL, et al. The effect of the aged garlic extract, "kyolic," on the development of experimental atherosclerosis. Atherosclerosis 132(1): 37–42, 1997.
⁸Schulz V, et al. Rational phytotherapy. New York: Springer-Verlag, 1998: 112.
⁹Silagy CA, et al. A meta-analysis of the effect of garlic on blood pressure. J Hypertens 12(4): 463–468, 1994.
¹⁰Warshafsky S, et al. Effect of garlic on total serum cholesterol. A meta-analysis. Ann Intern Med 119(7) Part 1: 599–605, 1993.
¹¹Auer W, et al. Hypertension and hyperlipidemia: Garlic helps in mild cases. Br J Clin Pract Symp 69 (Suppl.): 3–6, 1990.
¹²Santos OS de A, et al. Effects of garlic powder and garlic oil preparations on blood lipids, blood pressure and well being. Br J Clin Res 6: 91–100, 1995.
¹³Steinmetz KA, et al. Vegetables, fruit, and colon cancer in the Iowa Women's Health Study. Am J Epidemiol 139(1): 1–13, 1994.