Plant-based diets and mortality in Black and low-income Americans: findings from a large prospective cohort study

Plant-based diets have been widely promoted for their health and environmental benefits. However, the health benefits may differ by the quality (i.e. healthiness) of plant foods, and few studies have specifically evaluated the association of plant-based diets with mortality in Black and low-income Americans who disproportionately experience poor health outcomes.

We aimed to examine associations of plant-based dietary patterns with all-cause and cause-specific mortality in the Southern Community Cohort Study, a population-based prospective cohort conducted among predominantly Black and low-income Americans.

Included in this study were 77,797 participants. Plant-based dietary patterns were assessed by established indices [i.e. overall plant-based diet index (PDI), healthy plant-based diet index (hPDI), unhealthy plant-based diet index (uPDI)] based on dietary intakes collected using a validated food frequency questionnaire at baseline (2002-2009). Mortality data were ascertained through 2022. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations of PDI, hPDI, and uPDI with mortality from all, cardiovascular disease (CVD), cancer, and other nonexternal causes, adjusting for potential confounders.

During a median follow-up of 16.6 y, 27,269 deaths were identified. Compared with the lowest quintile, the highest quintile of PDI (HR = 0.87, 95% CI: 0.81, 0.93) and hPDI (HR = 0.82, 95% CI: 0.76, 0.89) was associated with reduced all-cause mortality (both P_trend < 0.001). In contrast, a high uPDI was linked to elevated all-cause mortality (HR = 1.17, 95% CI: 1.08, 1.26 for the highest compared with lowest quintile, P_trend < 0.001). Similar associations were observed for mortality from CVD and other causes. We also identified significant multiplicative interactions between hPDI and a composite measure of nondietary lifestyles in reducing all-cause and CVD mortality.

Adherence to a diet characterized by healthy plant foods and low animal foods may decrease mortality.