Catechins are polyphenol compounds in tea that are associated with many of tea's proposed health benefits.
Epigallocatechin gallate (EGCG), the most abundant catechin in tea, acts as an androgen antagonist and can suppress prostate cancer cell proliferation, suppress production of prostate-specific antigen (PSA) by prostate cancer cells, and increase prostate cancer cell death in vitro.
Results from one in vitro study showed that prostate cancer cells were less susceptible to radiation -induced apoptosis when exposed to EGCG 30 minutes before radiation exposure.
Oral intake of either a green tea catechin solution or EGCG alone was associated with reduced development of prostate cancer in studies with transgenic adenocarcinoma of the mouse prostate (TRAMP) mice.
Epidemiologic studies of Japanese men have generally not shown a relationship between reported green tea consumption and prostate cancer development, but at least one study has shown an association with the development of advanced prostate cancer.
Results from a small placebo-controlled study of green tea catechins in men with high-grade prostatic intraepithelial neoplasia (HGPIN) showed a statistically significant decrease in the development of prostate cancer among men who were randomly assigned to receive the catechin supplement. A larger, multicenter, randomized trial is now under way.
Studies of orally administered mixtures of tea catechins in men with prostate cancer have begun to provide information about biologic effects in this setting but are too preliminary to draw conclusions about clinical effectiveness.
Green tea has been well tolerated in clinical studies of prostate cancer patients, with the most common side effects being mild gastrointestinal symptoms.
General Information and History
Sailors first brought tea to England in 1644, although tea has been popular in Asia since ancient times. After water, tea is the most consumed beverage in the world. Tea originates from the C. sinensis plant, and the methods by which the leaves are processed determine the type of tea produced. Green tea is not fermented but is made by an enzyme deactivation step where intensive heat (i.e., roasting the freshly collected tea leaves in a wok or, historically, steaming the leaves) is applied to preserve the tea's polyphenols (catechins) and freshness. In contrast, the enzyme catalyzed polymerization and oxidation of catechins and other components produces darker colored black tea. Oolong, a third major type of tea, contains polyphenols that are partially oxidized.