Allium sativum, commonly known as garlic, is a species in the onion family and has been used throughout history for medicinal purposes, including a treatment for systemic yeast infections. Candidiasis is a term describing infections by yeasts that can range from superficial to systemic, which can infect many parts of the body. Treatment of such infections often requires prescription antifungal medications, such as the azoles, but increased usage of these drugs has led to evolutionary selection of yeasts with enhanced resistance to conventional drug therapy. Consult a health care professional before attempting to treat yeast infections with herbs.
Biologically Active Ingredient of Garlic
The garlic plant's bulb is the most commonly used part of the plant for both culinary and medicinal purposes. A biologically active component of the crushed bulb, a volatile substance named allicin, gives garlic its characteristic odor and is scientifically proven to have known antimicrobial properties. The antimicrobial activity of allicin is suspected to be due to its ability to inactivate essential enzymes responsible for pathogenic growth and reproduction of invasive species of yeast.
Causative Agent of Systemic Yeast Infections
Candida albicans, or C. albicans, is a form of yeast, which under normal circumstances can live in the human mouth and gastrointestinal tract with no harmful effects. These types of pathogen/host interactions are called commensal relationships. Infections occur when the innocuous, unicellular yeast-like form of C. albicans reacts to environmental signals and morphologically and chemically changes into an invasive, multicellular filamentous form. It is this multicellular form that can act as a causitive agent of opportunistic infections in humans. Systemic fungal infections--fungemias--have materialized as important causes of morbidity and mortality, especially in immunocompromised patients, such as those suffering from AIDS, cancer and/or transplantations. Additionally hospital-acquired infections are a major health concern due to C. albicans's ability to form protective layers, called biofilms.
Current Research
A study appearing in the December 2008 issue of the "Journal of Applied Microbiolology" sought to determine whether garlic extract has any effect on the morphological transformation of yeast, from its nonpathogenic single-celled form to the invasive and pathogenic multicellular form. The researchers used cells that were incubated with a range of concentrations of fresh garlic extract, and the morphology was monitored by microscopy. They found that treatment with extracts inhibited the transition of yeast. They concluded that garlic and its bioactive components have the ability to affect the expression level of genes necessary for this morphological transformation. In a December 2010 issue of "Free Radical Biology and Medicine," investigators researched various levels of allicin required to force invasive forms of yeast into genetically-programmed cell death. They treated yeast cells with chemically synthesized allicin, the pure form of allicin, or with allicin in garlic juice. They found that cell death was activated after all allicin treatments and concluded that it can effectively initiate preprogrammed cell death in yeast cells and further presents an alternative mechanism to kill cells by the inactivation of essential yeast enzymes used for transformation.
Further Studies
Lastly, in a study published in the April 2010 journal "Mycopathologia," the authors used allicin to demonstrate both its intrinsic antifungal activity and its synergic effect with the azoles in the treatment of yeast infections. In this study, six Candida species were investigated, and the results demonstrated the synergistic effects between allicin and azoles in some of the Candida species, such as C. albicans. But researchers noticed that this effect was not demonstrated in the majority of species tested. Nonetheless, the researchers concluded that clinical testing in humans needs to be performed to further support these findings.
References
- "Journal of Applied Microbiology"; Inhibition of hyphae formation and SIR2 expression in Candida albicans treated with fresh Allium sativum (garlic) extract; C. Low et al.; December 2008.
- "Mycopathologia"; In vitro investigation of antifungal activity of allicin alone and in combination with azoles against Candida species; A. Khodavandi et al.; April 2010.
- "Free Radical Biology and Medicine"; Allicin disrupts the cell's electrochemical potential and induces apoptosis in yeast; M. Gruhlke et al.; December 2010.
