A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagasaki (Japan)

Objectives: Laboratory and animal studies have shown a protective effect of green tea on cancer of different sites, but epidemiological evidence is li mited and inconclusive. This prospective study in Japan examined the associ ation between green tea consumption and cancer incidence. Methods: Subjects were 38,540 people (14,873 men, mean age 52.8 years; 23,6 67 women, mean age 56.8 years) who responded to a mail survey carried out b etween 1979 and 1981. A self-administered questionnaire ascertained consump tion frequency of green tea using precoded answers (never, once per day, tw ice to four times per day, and five or more times per day). Follow-up conti nued until 31 December 1994. The study analyzed solid cancers (n = 3881); h ematopoietic cancers (188); cancers of all sites combined (4069); and cance r of specific sites with more than 100 cases, i.e. stomach (901), colon (43 2), rectum (193), liver (418), gallbladder (122), pancreas (122), lung (436 ), breast (281), and bladder (122). Poisson regression was used to allow fo r city, gender, age, radiation exposure, smoking status, alcohol drinking, body-mass index, education level, and calendar time. Results: Green tea consumption was virtually unrelated to incidence of canc ers under study. The relative risks of all cancers for those consuming gree n tea twice to four times per day and five or more times per day were 1.0 ( 95% confidence interval 0.91-1.1) and 0.98 (0.88-1.1), respectively, as com pared with those consuming green tea once per day or less. Conclusion: Our findings do not provide evidence that regular green tea con sumption is related to reduced cancer risks.