The Lack of Association between Plant-Based Dietary Pattern and Breast Cancer: a Hospital-Based Case-Control Study

Our purpose was to assess the association between plant-based dietary patterns and breast cancer (BrCa) among Iranian women. This hospital-based case-control study included 150 newly diagnosed BrCa cases and 150 age-matched controls from the Cancer Research Center, Imam Khomeini hospital, Iran. Three indices of a plant-based diet were first calculated: plant-based diet index (PDI), the healthy PDI (hPDI), and the unhealthy PDI (uPDI). In the overall PDI, all plant foods scored positively. In hPDI and uPDI, healthy and less healthy plant foods scored positive, respectively. The adjusted odds ratio (OR) in the highest adherence of PDI was 1.00 (95% confidence interval [CI], 0.55–1.83). In hPDI, 0.89 (95% CI, 0.49–1.62); in uPDI, 1.80 (95% CI, 0.95–3.42). The adjusted OR after subgroup analysis for body mass index (BMI) was as follow, BMI > 25: 0.77(95% CI, 0.37–1.61) comparing highest with the lowest tertile of PDI, 0.91(95% CI, 0.44–1.89) comparing highest with the lowest tertile of hPDI and this value for uPDI was 2.04 (95% CI, 0.91–4.56). BMI < 25: OR for top tertile of PDI was 1.82 (95% CI, 0.48–6.93), top tertile of hPDI was 1.47 (95% CI, 0.35–6.22) and top tertile of uPDI was 2.29 (95% CI, 0.54–9.70). Our results revealed no significant association between none of the PDIs and the chance of BrCa in Iranian women. Continued and expanded research, evaluated by different methods and BrCa is urgently needed to build the foundation for future progress in evidence-based public health efforts.