This major new study was designed to determine whether caffeinated coffee and black tea consumption are associated with risk of breast cancer, both overall and by hormone receptor status. The study included 61,433 women in the Swedish Mammography Cohort who were initially cancer free and followed for an average of 17.4 years. Coffee consumption was found not to be associated with risk of breast cancer. However, drinking at least two cups of black tea per day was found to be associated with a small increase in overall breast cancer risk and ER+/PR+ tumors in particular compared with no black tea consumption.

Other studies report mixed conclusions regarding black tea and breast cancer

This study updates a previous January 2002 report concerning coffee and tea consumption and breast cancer in the Swedish Mammography cohort which found that consumption of coffee, tea, and caffeine were not associated with incidence of breast cancer. The majority of epidemiological studies have found no association or a modest negative association between tea intake and risk of breast cancer. Stronger associations have been found for several subsets of women and breast cancer types:
  • Drinking black tea has been found to be associated with a protective effect for those with lobular breast cancer
  • Women under 50 who consumed three or more cups of tea per day had a 37% lower risk of breast cancer than women under 50 reporting no tea consumption in one study
  • An inverse relationship between caffeine intake and breast cancer was found among postmenopausal women in one large study
  • A meta-analysis of five cohort studies found a small increase in breast cancer risk associated with black tea consumption; the authors concluded that the data suggested a possible late-stage, promotional effect of black tea on breast carcinogenesis.

Bottom line:   Moderate black tea consumption appears to be safe, but most women should not consume more than two cups per day.