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.