The Modulating Influence of Tea Polyphenols on Estrogen Metabolism in Asian and Caucasian Populations: Breast Cancer Prevention

High tea consumption seems to be one of the most important preventive dietary factors explaining the low incidence of breast cancer in East Asian women. The mechanisms responsible for the preventive effect of high tea consumption on sex-hormone related cancer risk are not clear, however, a modulating influence of tea on estrogen metabolism may play a very important role. Tea polyphenols (TPh) interact with different targets in steroid pathways, in particular inhibiting aromatase (which results in reducing levels of 17-beta-estradiol), modulating cytochrome P450 enzyme activity, and scavenging oxygen free radicals generated during redox-cycling of catechol estrogens (CEs), intermediates in estrogen metabolism. However, inconsistency in the results of epidemiological studies investigating relationships between tea intake and the risk of breast cancer may also be explained by polymorphism of genetic variants of catechol-O-methyltransferase ( COMT ), detoxifying enzyme shared by TPh and CEs. A lower risk of breast cancer in East Asia may result from an efficient detoxification of CEs due to high frequency of allele COMT G ∗ encoding an enzyme with a higher activity, and a high intake of tea in individuals with low-activity allele COMT A ∗ .