Plant-based dietary patterns and the risk of digestive system cancers in 3 large prospective cohort studies

Little is known about the relation between plant-based dietary patterns and digestive system cancers. This study investigated the prospective association between 3 pre-defined indices of plant-based dietary pattern and risk of digestive system cancers, as a whole or individually. We utilized data from 3 prospective cohorts, the Nurses' Health Study (1984-2018, 74,496 women aged 65 +/- 10.9 years), Nurses' Health Study II (1991-2017, 91,705 women aged 49.3 +/- 8.3 years), and Health Professionals Follow up Study (1986-2016, 45,472 men aged 65.4 +/- 11.0 years). We used Cox proportional hazards regression models to estimate multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) of digestive system cancers across 3 plant-based diet index scores: overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI). During a follow-up of 4,914,985 person-years, we identified 6,518 cases of digestive system cancers. In the pooled analysis of 3 cohorts, the HRs (95% CIs) per 10-point increase in hPDI score were 0.93 (0.89, 0.97) for total digestive system cancer, 0.94 (0.89, 0.99) for gastrointestinal tract cancer, 0.89 (0.81, 0.98) for accessory organ cancer, and 0.68 (0.52, 0.91) for liver cancer. In contrast, the HRs (95% CIs) per 10-point increase in uPDI score was 1.06 (1.01, 1.11) for gastrointestinal tract cancer and 1.07 (1.01, 1.13) for colorectal cancer. A healthy plant-based dietary pattern was associated with reduced risks of total digestive system cancers as well as individual cancers in the gastrointestinal tract and the accessory organs. Emphasizing the healthiness and quality of plant-based diets may be important for the prevention of developing cancers in the digestive system.