Mediterranean dietary pattern is associated with lower incidence of premenopausal breast cancer in the Seguimiento Universidad de Navarra (SUN) Project

OBJECTIVE: Due to the growing interest in the role of dietary patterns (DPs) on chronic diseases, we assessed the association between a posteriori identified DPs in the Seguimiento Universidad de Navarra (SUN) Project - a prospective cohort study in a Mediterranean country - and breast cancer (BC) risk. DESIGN: DPs were ascertained through a principal component analysis based on 31 predefined food groups. BC cases were initially identified through self-report or, if deceased, from death certificates or by notification by the next kin. Women reporting BC were asked to provide a copy of their medical report and diagnoses for confirmation purposes. We fitted Cox regression models to assess the association between adherence to the identified DPs and BC risk. SETTING: Spanish university graduates. PARTICIPANTS: We included 10 713 young and middle-aged - mainly premenopausal - women. RESULTS: After a median follow-up of 10·3 years, we identified 100 confirmed and 168 probable incident BC cases. We described two major DPs: 'Western dietary pattern' (WDP) and 'Mediterranean dietary pattern' (MDP). A higher adherence to a WDP was associated with an increased risk of overall BC (multivariable-adjusted HR for confirmed BC Q4 v. Q1 1·70; 95 % CI 0·93, 3·12; P for trend = 0·045). Contrarily, adherence to a MDP was inversely associated with premenopausal BC (multivariable-adjusted HR Q4 v. Q1 0·33; 95 % CI 0·12, 0·91). No significant associations were observed for postmenopausal BC. CONCLUSIONS: Whereas a higher adherence to the WDP may increase the risk of BC, a higher adherence to the MDP may decrease the risk of premenopausal BC.The study was supported by the “Acción Transversal del Cáncer", approved on the Spanish Ministry Council on the 11th October 2007, by the Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), by the Instituto de Salud Carlos III grants, cofunded by FEDER funds -a way to build Europe- PI08/1770 (to M. Kogevinas), PI09/0773 and FIS 12/00715 (to J. Llorca), PI09/1903 (to R. Peiró), PI09/2078 (to F.J. Caballero), PI09/1662 (to J.J. Jiménez- Moleón), PI11/01403 (to N. Aragonés), PI12/00150 (to B.Pérez- Gómez), PI12/00488 (to M.Pollán), by the Fundación Marqués de Valdecilla grant API 10/09 (to J. Llorca), by the Consejería de Salud of the Junta de Andalucía grant 2009-S0143 (to J. Alguacil), by the Conselleria de Sanitat of the Generalitat Valenciana grant AP061/10 (to R. Peiró), by the Regional Government of the Basque Country, by the Fundación Caja de Ahorros de Asturias, by the University of Oviedo and by the Spanish Ministry of Economyand Competitiveness Juan de la Cierva de Incorporación grant IJCI-2014-20900 (to A. Castelló). None of the funding institutions played any role in the present work. The content and views of this publication are those of the authors and do not necessarily reflect the official position of the Instituto de Salud Carlos III.S