Diet Quality and Breast Cancer Incidence in the Multiethnic Cohort

This study investigated the relation of diet quality indexes (DQI) with breast cancer incidence among women from the Multiethnic Cohort (MEC). Participants completed a questionnaire with a validated food frequency questionnaire. Scores for Healthy Eating Index 2015 (HEI-2015), Alternate Healthy Eating Index 2010 (AHEI-2010), alternate Mediterranean diet score (aMED), and Dietary Approaches to Stop Hypertension (DASH) were divided into quintiles (Q1-Q5). Cox regression was applied to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for DQIs and breast cancer risk adjusted for known risk factors. The respective HRs for Q5 vs. Q1 were: 1.06 (95% CI, 0.98-1.14) for HEI-2015, 0.96 (95% CI, 0.90-1.04) for AHEI-2010, 1.01 (95% CI, 0.94-1.09) for aMED, and 0.95 (95% CI, 0.88-1.02) for DASH (p(trend) > 0.05 for all). However, overweight and obesity were significantly associated with breast cancer incidence. Despite the null association for DQIs, diet quality may lower breast cancer risk through its positive influence on weight status.