Diabetes risk reduction diet and the risk of breast cancer

Objective: Diabetes and insulin levels may increase the risk of postmenopausal breast cancer. In the present investigation, we aimed at evaluating whether adherence to a diabetes risk reduction diet (DRRD) lowers the risk of breast cancer. Methods: We used data from an Italian, multicentric case-control study (1991-1994) including 2569 incident histologically-confirmed breast cancer cases and 2588 hospital controls. A food frequency questionnaire collected subjects' usual diet. We derived a DRRD score on the basis of eight items: intake of cereal fiber, total fruit, coffee, polyunsaturated to saturated fats ratio and nuts (higher scores for higher intakes), and dietary glycemic index, red/processed meat and sugar-sweetened beverages/fruit juices (higher scores for lower intakes). The score theoretically ranged 8-37, with higher values indicating greater DRRD adherence. Odds ratios (ORs) of breast cancer according to the DRRD score were estimated using multiple logistic regression models. Results: The DRRD score was inversely related to the risk of breast cancer. The ORs were 0.93 [95% confidence interval (CI), 0.89-0.98] for a three-point score increment and 0.76 (95% CI, 0.64-0.89) for the highest versus the lowest quartile (P for trend 0.001). Inverse associations were observed in subgroups of covariates. Conclusions: Higher DRRD adherence may decrease the risk of breast cancer.