A prospective study of healthful and unhealthful plant-based diet and risk of overall and cause-specific mortality.

Purpose: Although emphasis has recently been placed on the importance of diet high in plant-based foods, the association between plant-based diet and long-term risk of overall and cause-specific mortality has been less studied. We aimed to investigate whether plant-based diet was associated with lower death risk.

Methods: This prospective cohort study used data from the US National Health and Nutrition Examination Survey. Diet was assessed using 24 h dietary recalls. We created three plant-based diet indices including an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). Deaths from baseline until December 31, 2015, were identified. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression.

Results: We documented 4904 deaths among 40,074 participants after a median follow-up of 7.8 years. Greater adherence to PDI was associated with lower risk of overall (HR comparing extreme quintiles 0.80, 95% CI 0.73, 0.89, p < 0.001) and cancer-specific (HR = 0.68, 95% CI 0.55, 0.85, p < 0.001) mortality. These inverse associations remained for hPDI and overall mortality with a HR of 0.86 (95% CI 0.77, 0.95, p = 0.001), but not for cancer or CVD mortality. Conversely, uPDI was associated with higher risk of total (HR = 1.33, 95% CI 1.19, 1.48, p < 0.001) and CVD-specific (HR = 1.42, 95% CI 1.12, 1.79, p = 0.015) mortality.

Conclusions: Increased intake of a plant-based diet rich in healthier plant foods is associated with lower mortality risk, whereas a plant-based diet that emphasizes less-healthy plant foods is associated with high mortality risk among US adults.