AbstractThe role of diet on breast cancer risk is not well elucidated but animal food sources may play a role through, for example, the pathway of the insulin-like growth factor 1 system or cholesterol metabolism. The aim of this study was to evaluate the association between animal foods and the risk of postmenopausal breast cancer. This study was embedded in the Rotterdam Study, a population-based prospective cohort study of subjects aged 55 years and over (61 % female). Dietary intake of different animal foods was assessed at baseline using a validated FFQ and adjusted for energy intake using the residual method. We performed Cox proportional hazards modelling to analyse the association between the intake of the different food sources and breast cancer risk after adjustment for socio-demographic, lifestyle and metabolic factors. During a median follow-up of 17 years, we identified 199 cases of breast cancer (6·2 %) among 3209 women. After adjustment for multiple confounders, no consistent association was found between the intake of red meat intake, poultry, fish or dairy products and breast cancer risk. However, we found that egg intake was significantly associated with a higher risk of breast cancer (hazard ratio_{Q4 v. Q1}: 1·83; 95 % CI 1·20, 2·79; P_trend=0·01). In conclusion, this study found that dietary egg intake but no other animal foods was associated with a higher risk of postmenopausal breast cancer. Further research on the potential mechanisms underlying this association is warranted.