Abstract Context Plant-based dietary patterns have been associated with a lower risk of several types of cancer. Yet, their specific association with breast cancer (BC) risk and survival remains unclear. Objective To evaluate the association of adherence to a plant-based diet index (PDI), unhealthful plant-based diet index (uPDI), and healthful plant-based diet index (hPDI) with BC risk and BC-specific mortality. Data sources The Web of Science, Scopus, and PubMed databases were searched from inception to August 2025. Data extraction Case-control and cohort studies evaluating the association among the PDI, hPDI, and uPDI with BC risk and BC mortality in cancer-free participants at baseline and in BC survivors were reviewed. Details of the studies and main outcomes were extracted independently by 2 researchers. Data analysis Among 3020 records screened, 5 cohort and 4 case-control studies met the inclusion criteria. The PDI was not associated with BC risk in case-control (odds ratio OR = 0.72; 95% CI, 0.42-1.25) and cohort studies (hazard ratio HR = 0.96; 95% CI, 0.90-1.03). Participants with higher adherence to the hPDI had a lower BC risk in case-control (OR = 0.61; 95% CI, 0.49-0.77) and cohort studies (HR = 0.91; 95% CI, 0.86-0.97). Higher adherence to the uPDI was associated with increased BC risk in case-control (OR = 1.63; 95% CI, 1.20-1.22) and cohort studies (HR = 1.06; 95% CI, 0.98-1.15). Conclusions Higher adherence to the hPDI was associated with reduced BC risk, whereas adherence to the uPDI was associated with increased BC risk. Studies are needed to evaluate the role of plant-based diets in BC prognosis and survival. Systematic Review Registration PROSPERO registration No. CRD420251115296
Jiménez et al. (2025) studied this question.