Plant-based diets and total and cause-specific mortality: a meta-analysis of prospective studies

The adherence to plant-based diets has been shown to positively impact longevity by reducing the incidence and severity of lifestyle-related diseases. Previous studies on the association of plant-based dietary pattern, as evaluated by plant-based dietary index (PDI), healthy plant-based dietary index (hPDI) and unhealthy plant-based dietary index (uPDI), with mortality risk have reported inconsistent results. We performed the present meta-analysis to summarize evidence on this association and to quantify the potential dose-response relationship based on all available cohort studies.

A comprehensive literature search and systematic review of relevant articles up to October 2024 was performed in PubMed and Scopus. The summary risk estimates (RR) with 95% confidence interval (CI) for the highest versus the lowest category of PDIs, hPDIs and uPDIs were calculated. Dose-response meta-analysis was also performed for studies reporting categorical risk estimates for at least three quantitative levels of PDIs, hPDIs and uPDIs.

A total of 11 eligible cohort studies (13 datasets) were eventually included in this meta-analysis. Participants in the highest quintile of both the PDI and hPDI had a significantly decreased risk of all-cause mortality (pooled HR_PDI = 0.85; 95% CI: 0.80-0.90; pooled HR_hPDI = 0.86; 95% CI: 0.81-0.92) compared to participants in the lowest quintile. In contrast, the highest uPDI was associated with an increased risk of mortality (pooled HR_uPDI = 1.20; 95% CI: 1.11-1.31). Dose-response meta-analysis showed that there was a non-linear relationship between PDI or hPDI level and all-cause mortality (p = 0.001 and p < 0.001 for non-linearity, respectively). No evidence of a non-linear relationship was observed for uPDI (p = 0.596 for non-linearity).

Greater adherence to PDI or hPDI dietary pattern was associated with a lower risk of mortality, whereas uPDI dietary pattern was positively associated with mortality risk. Thus, promoting a plant-based dietary pattern may be a key strategy in improving public health and reducing the burden of diet-related mortality.