A case–control study of breast cancer and dietary intake of individual fatty acids and antioxidants in Montreal, Canada

This case–control study was conducted among French-Canadians to assess the association between breast cancer risk and specific fatty acids, and to investigate if breast cancer risk associated with individual polyunsaturated fatty acids differs in regard to antioxidant intakes. A total of 414 cases and 429 population-based controls were interviewed between 1989 and 1993. Dietary intake was assessed by a food-frequency questionnaire. No overall association was found between specific fatty acids and breast cancer risk, after adjustment for risk factors and total energy intake. In postmenopausal women with low vitamin E intake, there was an inverse and dose-dependent relationship between arachidonic acid and breast cancer risk [odds ratio (OR)=0.41; 95% confidence interval (CI) (0.20–0.82); P=0.02], while those with high vitamin E intake exhibited a significantly elevated risk [OR=2.46; 95% CI (1.12–5.39); P=0.024] when comparing the upper to the lower quartiles. The possible role of the interaction effect between arachidonic acid and vitamin E in breast cancer risk requires further investigation.