Cancer-preventive effects of drinking green tea among a Japanese
                       population

                       Imai K, Suga K, Nakachi K
                       Department of Epidemiology, Saitama Cancer Center Research Institute,
                       Japan.
                       Prev Med 1997 Nov-Dec;26(6):769-75

                       BACKGROUND: Laboratory studies have revealed the cancer preventive
                       effects of green tea, so the association between green tea consumption and
                       cancer was examined in a human population. METHODS: The association
                       between green tea consumption and cancer incidence was studied in our
                       prospective cohort study of a Japanese population. We surveyed 8,552
                       individuals over 40 years of age living in a town in Saitama prefecture on their
                       living habits, including daily consumption of green tea. During the 9 years of
                       follow-up study (71,248.5 person-years), we identified a total of 384 cases of
                       cancer in all sites. RESULTS: We found a negative association between green
                       tea consumption and cancer incidence, especially among females drinking
                       more than 10 cups a day. The slowdown in increase of cancer incidence with
                       age observed among females who consumedmore than 10 cups a day is
                       consistent with the finding that increased consumption of green tea is
                       associated with later onset of cancer. Age-standardized average annual
                       incidence rate was significantly lower among females who consumed large
                       amounts of green tea. Relative risk (RR) of cancer incidence was also lower
                       among both females (RR = 0.57, 95% CI = 0.33-0.98) and males (RR = 0.68,
                       95% CI = 0.39-1.21) in groups with the highest consumption, although the
                       preventive effects did not achieve statistical significance among males, even
                       when stratified by smoking and adjusted for alcohol and dietary variables.
                       CONCLUSION: Our epidemiological study showed that green tea has a
                       potentially preventive effect against cancer among humans.