Epidemiological and laboratory studies provide insight into the anticarcinogenic potential of garlic and its constituent compounds. Both water- and
lipid-soluble allyl
sulfur compounds are effective in blocking a myriad of chemically induced
tumors. Part of the protection from these compounds probably relates to a block in
nitrosamine formation and metabolism. However, blockage in the initiation and promotion phases of the carcinogenicity of various compounds, including
polycyclic hydrocarbons, provide evidence that garlic and its constituents can alter several phase I and II
enzymes. Their ability to block experimentally induced
tumors in a variety of sites including skin, mammary and colon, suggests a general mechanism of action. Changes in DNA repair and in immunocompetence may also account for some of this protection. Some, but not all, allyl
sulfur compounds can also effectively retard
tumor proliferation and induce apoptosis. Changes in cellular
thiol and phosphorylation stains may account for some of these antitumorigenic properties. The anticarcinogenic potential of garlic can be influenced by several dietary components including specific
fatty acids,
selenium, and
vitamin A. Since garlic and its constituents can suppress
carcinogen formation,
carcinogen bioactivation, and
tumor proliferation it is imperative that
biomarkers be established to identify which individuals might benefit most and what intakes can occur with ill consequences.