Healthful and Unhealthful Plant-Based Diets and Their Association with Cardiometabolic Targets in Women Diagnosed with Breast Cancer: A Cross-Sectional Analysis of a Lifestyle Trial

Background: Plant-based diets are recommended in guidelines for the prevention of cancer and cardiometabolic diseases, which remain major causes of death in breast cancer survivors (BCS). Since not all plant foods are healthy, we calculated the plant-based dietary index (PDI), healthy (hPDI) and unhealthy (uPDI), and their associations with cardiometabolic targets in BCS. Methods: Baseline dietary and cardiometabolic data were derived from 492 (median age 51, IQR 46–59) female BCS participating in a multicentric lifestyle trial conducted in Italy. Dietary data were collected with 7-day food records. PDI, hPDI, and uPDI were calculated by assigning positive scores to all plant foods, healthy plant foods or less healthy plant foods, respectively, as defined by the literature (scores ranged from 18 to 90). Using logistic or multinomial regression models, we estimated the odds ratios (OR) and the corresponding 95% confidence intervals (CI) between PDIs and cardiometabolic risk factors. Results: The OR of being obese (BMI ≥ 30 Kg/m²) was 0.47 (95%CI: 0.29–0.77), 0.37 (95%CI: 0.22–0.61) and 1.38 (95%CI: 0.83–2.28) with higher PDI, hPDI and uPDI, respectively. The OR of having a large waist circumference (≥88 cm) was 0.64 (95%CI: 0.42–1.00) with higher hPDI. The OR for hypercholesterolemia (≥200 mg/dL) was 1.80 (95%CI: 1.16–2.78) with higher uPDI. The ORs of hypertriglyceridemia (≥150 mg/dL) and metabolic syndrome were 0.38 (95%CI: 0.20–0.71) and 0.59 (95%CI: 0.35–0.97), respectively, with higher PDI. No other significant association was observed. Conclusions: Maintaining cardiometabolic risk factors within normal ranges is clinically relevant in BCS, and this may be more likely when a plant-based diet is consumed, especially if low in unhealthy plant foods.