Cancer Prevention with Green Tea Polyphenols

Abstract

Consumption of green tea (Camellia sinensis) has been suggested to have beneficial health effect, including cancer prevention. Extensive studies have established that the active cancer preventive constituents in green tea are a group of polyphenols. Green tea polyphenols display anticancer activity in many organ sites in different experimental models in rodents and in cultured cell lines in vitro. Treatment with green tea polyphenols leads to the inhibition of cancer cell proliferation, cancer-associated angiogenesis, and metastasis, as well as the induction of cancer cell apoptosis. Experimental studies demonstrate that these activities are likely resulted from the antioxidant activity and the direct binding of green tea polyphenols to proteins, resulting in the modulation of multiple cellular signaling pathways. The findings of polyphenol binding proteins reveal the mechanisms of the effectiveness and specificity of the anticancer actions. However, the inverse association between of green tea consumption and cancer risk is supported by epidemiological studies, but not all. This inconsistence may due to the lower blood and tissue levels of polyphenols from green tea drink, and may also depend on various etiology factors. Using much higher doses, results from some interventional studies support the safety and effectiveness of green tea polyphenols in cancer prevention. Well-designed clinical studies are required to fully evaluate the usefulness of green tea polyphenols in cancer prevention.