Breast cancer (BC) is the most frequently diagnosed cancer in the world. Preventive strategies represent a public health priority. Dietary interventions for preventing BC have been evaluated, mainly using observational designs, with inconsistent results. In this context, polyphenols have shown in vitro and in vivo beneficial properties and anticancer mechanisms. Polyphenols are a wide family of phytochemicals present in diverse foods. Their role in chronic disease prevention including cardiovascular diseases and cancer has been repeatedly suggested. For this reason, we evaluated total polyphenol intake in association with the risk of BC in the SUN Project - a prospective cohort study in a Mediterranean population.
We included 10,709 middle-aged, Spanish female university graduates. Polyphenol intake was assessed using a validated semi-quantitative 136-item food frequency questionnaire and matching food consumption data with the Phenol-Explorer database. Diagnosis of BC was self-reported or by the next of kin or identified from death certificates. Self-reports of a medically-diagnosed BC were confirmed using medical records. Cox regression models were fitted to estimate multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) for the association between terciles of adherence to the total polyphenol intake and BC risk.
After 10.3 years of median follow-up, 83 confirmed and 165 probable incident BC cases were identified. We observed a statistically significant inverse association between total polyphenol intake and BC risk for postmenopausal women when probable BC cases were used as outcome: HR for highest vs lowest tertile of total polyphenol intake 0.47 (95% CI 0.22-0.97; P for trend=0.041). No further significant associations were observed between total polyphenol intake and incident BC when total BC incidence or risk of premenopausal BC were considered.
Despite the small number of incident BC cases observed in this Mediterranean cohort, we observed that the higher total polyphenol intake, the lower risk of BC among postmenopausal women.
Clinical trial identification
Legal entity responsible for the study
Universidad de Navarra.
The SUN Project has received funding from the Spanish Government-Instituto de Salud Carlos III, and the European Regional Development Fund (FEDER) (RD 06/0045, CIBER-OBN, Grants PI10/02658, PI10/02293, PI13/00615, PI14/01668, PI14/01798, PI14/01764, and G03/140), the Navarra Regional Government (45/2011, 122/2014), and the University of Navarra.
All authors have declared no conflicts of interest.