Green Tea and Breast Cancers Link Questioned

TOKYONo association between green tea drinking and risk of breast cancer was found, according to a population-based prospective cohort study published in Breast Cancer Research (2010;12:R88). Findings from epidemiological studies have been inconsistent even though many in-vitro and animal studies have demonstrated a protective effect of green tea against breast cancer , and whether high green tea intake reduces the risk of breast cancer remains unclear. As a result, a Japan Public Health Center-based Prospective Study was conducted. A total of 581 cases of breast cancer were newly diagnosed in 53,793 women during 13.6 years' follow-up from the baseline survey in 1990 to 1994. After the five-year follow-up survey in 1995 to 1998, 350 cases were newly diagnosed in 43,639 women during 9.5 years' follow-up. The baseline questionnaire assessed the frequency of total green tea drinking while the five-year follow-up questionnaire assessed that of two types of green tea, sencha and bancha/genmaicha, separately.

Compared with women who drank less than 1 cup of green tea per week, the adjusted hazard ratio (HRs) for women who drank 5 or more cups per day was 1.12 in the baseline data. Similarly, compared with women who drank less than 1 cup of sencha or bancha/genmaicha per week, adjusted HRs for women who drank 10 or more cups per day were 1.02 for sencha and 0.86 for bancha/genmaicha. No inverse association was found regardless of hormone receptor-defined subtype or menopausal status.