• Department of Hepatobiliary Surgery, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China. Electronic address: gczhong1991@hospital.cqmu.edu.cn.
• Department of Breast and Thyroid Surgery, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.
• The Second Student Office, the Second College of Clinical Medicine, Chongqing Medical University, Chongqing, China.
• Department of Nutrition and Food Hygiene, School of Public Health and Management, Chongqing Medical University, Chongqing, China.
• Department of Infectious Diseases, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.
• Department of Nephrology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.

BACKGROUND: Plant-based diets have been recommended for improving health outcomes, including cancer. However, previous studies on plant-based diets and the risk of pancreatic cancer are scarce and fail to consider plant food quality.

OBJECTIVES: We sought to examine the potential associations of 3 plant-based diet indices (PDIs) with the risk of pancreatic cancer in a US population.

METHODS: A population-based cohort of 101,748 US adults was identified from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. The overall PDI, healthful PDI (hPDI), and unhealthful PDI (uPDI) were constructed to qualify adherence to overall, healthy, and less healthy plant-based diets, respectively, with higher scores indicating better adherence. Multivariable Cox regression was used to compute hazard ratios (HRs) for pancreatic cancer incidence. Subgroup analysis was conducted to identify the potential effect modifiers.

RESULTS: Over a mean follow-up of 8.86 years, 421 pancreatic cancer cases occurred. Participants in the highest compared with the lowest quartiles of overall PDI had a lower risk of pancreatic cancer [HR_{quartile 4 versus 1}: 0.74; 95% confidence interval (CI): 0.57, 0.96; P_trend = 0.023]. A stronger inverse association was observed for hPDI (HR_{quartile 4 versus 1}: 0.56; 95% CI: 0.42, 0.75; P_trend < 0.001). Conversely, uPDI was positively associated with the risk of pancreatic cancer (HR_{quartile 4 versus 1}: 1.38; 95% CI: 1.02, 1.85; P_trend = 0.012). Subgroup analyses revealed a stronger positive association for uPDI in participants with BMI <25 (HR_{quartile 4 versus 1}: 3.22; 95% CI: 1.56, 6.65) than in those with BMI ≥25 (HR_{quartile 4 versus 1}: 1.08; 95% CI: 0.78, 1.51) (P_interaction = 0.001).

CONCLUSIONS: In this US population, adherence to a healthy plant-based diet confers a lower risk of pancreatic cancer, whereas adherence to a less healthy plant-based diet confers a higher risk. These findings highlight the importance of considering plant food quality in preventing pancreatic cancer.