The association between plant-based dietary patterns and risk of breast cancer: a case-control study.

Affiliation

Rigi S(1), Mousavi SM(1)(2), Benisi-Kohansal S(1), Azadbakht L(1)(3), Esmaillzadeh A(4)(5)(6).
Author information:
(1)Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, P.O. Box 14155-6117, Tehran, Iran.
(2)Students' Scientific Research Center
(SSRC), Tehran University of Medical Sciences, Tehran, Iran.
(3)Diabetes Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
(4)Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, P.O. Box 14155-6117, Tehran, Iran. [Email]
(5)Obesity and Eating Habits Research Center, Endocrinology and Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran. [Email]
(6)Department of Community Nutrition, School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran. [Email]

Abstract

Limited data are available, linking the plant-based diets to breast cancer (BC). We examined the association of overall plant-based diet index (PDI), hypothesized healthful (hPDI) and unhealthful versions of a plant-based diet index (uPDI) with BC in Iranian women. This population-based case-control study included 350 cases with newly diagnosed BC and 700 age-matched apparently healthy controls. We collected dietary data using a validated, Willett-format semi-quantitative food frequency questionnaire. Using these data, we generated a PDI by dedicating positive scores to plant foods, and reverse scores to animal foods, hPDI by assigning positive scores to healthy plant foods and reverse scores to less healthy plant foods and animal foods, and finally uPDI in which positive scores were assigned to less healthy plant foods and reverse scores to healthy plant foods and animal foods. After controlling for potential confounders, individuals in the highest quartile of PDI had 67% lower odds of BC than those in the lowest quartile (OR 0.33; 95% CI 0.22-0.50). Individuals with the greatest adherence to hPDI were 36% less likely to have BC than those with the lowest adherence, in the fully adjusted model (OR 0.64; 95% CI 0.43-0.94). In terms of uPDI, women in the top quartile had a 2.23 times greater chance of BC than those in the bottom quartile (OR 2.23; 95% CI 1.48-3.36). Greater adherence to PDI and hPDI was inversely associated with the risk of BC, whereas uPDI was associated with an increased risk.