Biological and epidemiological evidence supports an inverse association of phenolic acids with obesity-related chronic diseases. However, no previous study has prospectively evaluated the relationship between subclasses and individual compounds of phenolic acids and the risk of postmenopausal breast cancer, one of the most important and prevalent obesity-related cancer sites.This study examined associations between subclasses of phenolic acids, including hydroxycinnamic and hydroxybenzoic acids intake, and risk of breast cancer.The Seguimiento Universidad de Navarra (SUN) Project is a dynamic, permanently open prospective cohort which started in 1999.Participants were 10,812 middle-aged women. All of them were university graduates.Usual diet was assessed at baseline and after 10 years of follow-up with a 136-item food frequency questionnaire. Phenolic acid intake was calculated by matching food consumption with the Phenol-Explorer database on phenolic acids content of each reported food item.Participants were classified according to tertiles of subclasses or individual compounds of phenolic acids. Cox regression models were fitted to estimate multivariable-adjusted hazard ratios and 95% CIs for breast cancer incidence.Over an average of 11.8 years of follow-up, 101 incident cases of breast cancer were confirmed. After multivariable adjustment, an inverse association between hydroxycinnamic acids intake and breast cancer was observed (hazard ratio third tertile vs first tertile 0.37, 95% CI 0.16 to 0.85; P for trend=0.029) among postmenopausal women. Specifically, chlorogenic acids (3-, 4-, and 5- caffeoylquinic acids) showed the strongest inverse association (hazard ratio third tertile vs first tertile 0.33, 95% CI 0.14 to 0.78; P for trend=0.012).A higher intake of hydroxycinnamic acids, especially from chlorogenic acids-present in coffee, fruits, and vegetables-was associated with a lower incidence of breast cancer among postmenopausal women. Future observational studies are needed to corroborate these results.
