Crushing garlic
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When you bite into fresh garlic -- or cut it or crush it -- it develops a component called allicin from the precursor component alliin. Allicin has antibacterial, antifungal and antiviral properties, according to the University of Maryland Medical Center. Allicin is beneficial to a number of health conditions, but never try to self-treat any condition with garlic. The UMMC recommends taking herbs only with the supervision of a health-care provider qualified in botanical medicine.

Components of Fresh Garlic

Alliin is a chemical compound derived from the amino acid cysteine. It is odorless, although it contains sulfur. When garlic is cut or crushed, alliin comes in contact with the enzyme allinase, which converts alliin to allicin. Allicin is a main reason for the pungent odor of garlic and appears responsible for many of its health benefits, explains the UMMC.

Considerations Before Use

Although allicin has beneficial effects, the human body does not absorb it effectively, according to the UMMC. Supplement manufacturers ferment aged garlic to break allicin down to water-soluble and oil-soluble sulfur-containing chemical compounds that the body can better absorb. These components of aged garlic provide health benefits for reducing cholesterol levels and for preventing heart disease and cancer. Fermented aged garlic supplements contain little to no allicin, however, and garlic supplements not standardized for allicin may not contain any of this substance. Because some supplement manufacturers believe allicin is the main active ingredient in garlic, they use processes that stabilize alliin and prevent it from breaking down into allicin until the garlic is consumed. It is unclear whether these processes work very well, explains the University of Southern California University Hospital.


A review published in the February 2009 issue of "Bioscience, Biotechnology and Biochemistry" notes that allicin has a variety of antimicrobial properties. It has antiviral effects and also is effective against a wide range of bacteria, including drug-resistant strains of staph infections. The UMMC reports that topical application of garlic may help treat fungal skin conditions such as Tinea corporis, known as ringworm.

Use and Dosage

Garlic supplements with high allicin content are marketed for their ability to fight bacterial, fungal and viral infections. A typical dosage as detailed by the UMMC is two 200-milligram freeze-dried tablets taken three times per day, with tablets standardized to at least 0.6 percent allicin. Some supplements are standardized to contain 10 to 12 milligrams/Gm alliin and 4,000 micrograms of total allicin potential, which may be listed on the label as TAP.