RESUMEN
OBJECTIVES: Previous studies assessed the link between plant based diet and breast cancer risk rather than healthy and unhealthy plant based diet. This study examined the relation between plant-based dietary pattern and risk of breast cancer among Iranian women. METHODS: This hospital-based case-control study was conducted among 412 women with pathologically confirmed breast cancer within the past year and 456 apparently healthy controls. Dietary data were collected using a validated and reliable 168-item FFQ. We created three patterns including overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). The risk of breast cancer was compared across quartiles of PDI, hPDI, and uPDI. RESULTS: we did not find significant association between adherence to PDI and uPDI score and odds of breast cancer among women. However, a greater score of hPDI was inversely associated to the risk of breast cancer (OR: 0.63; 95% CI: 0.43-0.93, P = 0.01), in the crude model. After adjustment for age and energy, we saw stronger association between breast cancer risk and higher hPDI score (OR: 0.55; 95% CI: 0.37-0.82, P = 0.002). After stratified by menopausal status, we did not find significant association between PDI and uPDI score and risk of breast cancer. However, pre- and postmenopausal women in the highest quartile of hPDI score had lower risk of breast cancer than those in the lowest quartile. CONCLUSIONS: we found an inverse significant association between hPDI and odds of breast cancer in the whole population of study. After stratifying by menopausal status, this correlation was also seen both in pre and postmenopausal women.