Polyphenols are a wide family of phytochemicals present in diverse foods. They might play a role in cancer development and progression. In vivo and in vitro studies have suggested beneficial properties and potential mechanisms. We aimed to evaluate the association between total and main classes of polyphenol intake and breast cancer (BC) risk in the Seguimiento Universidad de Navarra project - a prospective Mediterranean cohort study. We included 10 713 middle-aged, Spanish female university graduates. Polyphenol intake was derived from a semi-quantitative FFQ and matching food consumption data from the Phenol-Explorer database. Women with self-reported BC were asked to return a copy of their medical report for confirmation purposes; death certificates were used for fatal cases. Cox models were fitted to estimate multivariable-adjusted hazard ratios (HR) and 95 % CI for the association between tertiles (T) of polyphenol intake and BC. After 10·3 years of median follow-up, 168 probable incident BC cases were identified, out of which 100 were confirmed. We found no association between polyphenol intake and the overall BC risk. Nevertheless, we observed a significant inverse association between total polyphenol intake and BC risk for postmenopausal women, either for probable or only for confirmed cases (HRT3 v. T1 0·31 (95 % CI 0·13, 0·77; Ptrend=0·010)). Also, phenolic acid intake was inversely associated with postmenopausal BC. In summary, we observed no significant association between total polyphenol intake and BC risk. Despite a low number of incident BC cases in our cohort, higher total polyphenol intake was associated with a lower risk of postmenopausal BC.
Keywords: Breast cancer; Cohort studies; Polyphenols; Postmenopausal breast cancer; Seguimiento Universidad de Navarra project.