Abstract
As part of a population‐based case‐control study on diet and breast cancer in Spain, the role of dietary fat and vegetable oils in breast cancer etiology was examined. A validated, semi‐quantitative food‐frequency questionnaire was completed by 762 women, 18‐75 years of age, with histologically confirmed, newly diagnosed breast cancer, and 988 randomly selected female controls. For each food item and nutrient, the study subjects were divided into quartiles according to intake levels, with the lowest quartile serving as the reference category. Adjustment for total energy intake and other potential confound‐ers was made using multiple logistic regression for all women as well as separately for pre‐ and post‐menopausal women. Neither total fat intake nor specific types of fat were significantly associated with breast cancer in pre‐ or post‐menopausal women. However, higher consumption of olive oil (rich in monounsaturated fat) was significantly related to a lower risk of breast cancer [for highest vs. lowest quartile of consumption, odds ratio (OR) = 0.66; 95% Cl, 0.46‐0.97] with a significant dose‐response trend. While these findings do not support a relation between total fat intake and breast cancer risk, they do provide evidence for an inverse association between olive oil (and suggest one between monounsaturated fat) and risk of breast cancer.