Life-style related factors, particularly diet, are considered to be the major contributors to prostate cancer. Key cancer researches had shown that a diet including functional foods could result in a substantial reduction in the incidence of the clinically detectable prostate cancer. Of all dietary components, the most compelling evidence for chemopreventive effects has been accumulated for the active component of green tea -Epigallocatechin-3-Gallate (EGCG).

Several epidemiological studies have found a lower incidence of prostate cancer in Asian countries (where green tea is consumed regularly) compared to Western populations. Furthermore, Asian immigrants to US who have abandoned original dietary habits soon develop the same Western risk of prostate cancer, which is associated with Western lifestyle.

Another cancer research conducted in China showed that green tea consumption was protective against this disease. Also, closer here, a study was performed with sixty male volunteers with high grade prostate intraepithelial neoplasia, a premalignant condition of prostate growth that is known to result in a substantial number of cancers within 1 year after repeated biopsy. Half of the men consumed three 200 mg decaffeinated green tea catechin preparations orally, daily for 1 year, which resulted in a 90% reduction in the rate of HG-PIN positive men metastatic cancer with no significant side effects.