Objective: The purpose of our study was to examine the association of regular tea consumption with the risk of breast cancer in a large population-based case-control study from the United States.
Methods: Five thousand and eighty-two women with incident breast cancer between the ages of 20 and 74 years old from population-based cancer registries in Wisconsin, Massachusetts, and New Hampshire and 4,501 age-matched controls from lists of licensed drivers and Medicare beneficiaries completed a structured telephone interview that included information on usual tea consumption 5 years prior to the interview and other breast cancer risk factors. Logistic regression was used to obtain covariate-adjusted odds ratios and 95% confidence intervals associated with quantities of tea consumed.
Results: Tea consumption was not related to breast cancer risk overall (P for trend = 0.18). However, when stratified by age, an inverse association was observed among women less than 50 years: those consuming three or more cups per day had a 37% reduced breast cancer risk when compared with women reporting no tea consumption (age and study site-adjusted odds ratios, 0.63; 95% confidence intervals, 0.44-0.89; P = 0.01) with a significant test for trend (P = 0.01). The inverse association noted among younger women was consistent for in situ and invasive breast cancer, and for ductal and lobular breast cancer. All results were unchanged after adjustment for established risk factors.
Conclusion: We observed evidence to support a potential beneficial influence for breast cancer associated with moderate levels of tea consumption (three or more cups per day) among younger women. Further research is needed to confirm this association.