UC Irvine

Introduction: Diet has been implicated as a significant risk factor in terms of breast cancer progression and manifestation, but results are shaky when assessing the specific role played by diet. The Healthful Diet Score was developed using a-priori based methods that assessed the existing nutritional epidemiology evidence regarding breast cancer risk along with findings from widely-accepted standardized dietary indices: Alternate Mediterranean Diet Index, Alternative Healthy Eating Index-2010, Dietary Approach to Stop Hypertension (aMED, AHEI-2010, DASH). An increased diet quality score is indicative of greater adherence to healthy dietary patterns, which encompass all beneficial aspects of dietary consumption ranging from vitamins to polyunsaturated fat consumption. Breast cancer is the most common cancer observed amongst women in which many risk factors have been identified, including some modifiable factors such as diet. We assessed the role of overall diet quality, through our own a-priori index and standardized indices, on the risk of incident breast cancer (BRCA). Methods: California Teacher Study participants were women age 22-104 years old at baseline (1995-1996) who are members of California State Teachers Retirement System. Overall diet quality scores were computed for the eligible study population (n=94,404) through participants’ responses to the validated-FFQ. Descriptive statistics across the various measures of overall diet quality were generated. Multivariate Cox proportional hazard regression models were constructed to provide hazard ratios and corresponding 95% confidence intervals. Results: In terms of overall breast cancer risk, overall diet quality as defined by AHEI-2010 exhibited the greatest reduction of risk 13% for the highest adherers vs. lowest adherers (HRQ5vsQ1 0.87, 95% CI: 0.79-0.97). Similar reductions in overall breast cancer risk were also exhibited in the highest adherers of a DASH diet plan (HRQ5vsQ1 0.88, 95% CI: 0.79-0.97). In terms of pre-menopausal breast cancer risk, overall diet quality was not significantly associated with breast cancer risk across all measure of diet quality. When assessing the post-menopausal subgroup in this study, the role of overall diet quality became increasingly apparent in terms of breast cancer risk in which the highest risk reduction observed was 25% for highest adherers of the AHEI-2010 diet pattern (HRQ5vsQ1 0.75, 95% CI:0.70-0.91). Conclusion: Findings from this large prospective cohort study suggest that overall diet quality is significantly associated with invasive breast cancer risk amongst post-menopausal women, and the AHEI-2010 score displayed the strongest inverse association with breast cancer.