Background: Trans fatty acids (TFAs) have been hypothesized to influence breast cancer risk. However, relatively few epidemiologic studies have examined this association, and analyses stratified by breast cancer immunophenotype and menopausal status remain limited.
Objective: To evaluate the association between dietary intake of trans fatty acids and breast cancer immunophenotypes in Mexican women.
Methods: We conducted a case–control analysis including 1,045 incident breast cancer cases and 1,030 population-based controls from a study carried out between 2007 and 2011 in Northern Mexico. Information on estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression was obtained from medical records to classify tumors into immunophenotypes. Dietary intake was assessed using a semi-quantitative food frequency questionnaire. Intakes of total trans fatty acids, industrial trans fatty acids, and ruminant trans fatty acids were estimated using the United States Department of Agriculture (USDA) food composition database. Unconditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for associations between trans fatty acid intake and breast cancer overall and by immunophenotype.
Results: Higher intake of industrial trans fatty acids was strongly associated with increased odds of breast cancer (OR for tertile 3 vs. tertile 1: 18.8; 95% CI: 11.8–27.1; P-trend <0.001). Similarly, higher consumption of ruminant trans fatty acids was associated with elevated breast cancer odds (OR for tertile 3 vs. tertile 1: 8.8; 95% CI: 6.5–11.8; P-trend <0.001). These positive associations were observed across all breast cancer immunophenotypes and among both premenopausal and postmenopausal women.
Conclusions: These findings support the hypothesis that higher dietary intake of trans fatty acids—particularly industrial trans fatty acids—is associated with increased breast cancer risk. Further longitudinal and mechanistic studies are warranted to elucidate the biological pathways underlying these associations.