Plant-based diet quality and the risk of total and disease-specific mortality: A population-based prospective study

Plant-based diets have been suggested to have health benefits, and risk differs by quality of plant foods. However, evidence on the association between the quality of plant-based diets and mortality are limited. This study examined the associations between 3 different types of plant-based diet indices and risk of total and disease-specific mortality.

Analyses were based on a population-based cohort of 118,577 South Korean adults (40-69 years of age) who participated in the Korean Genome and Epidemiology Study_Health Examinees (2004-2019). Dietary intakes were assessed using a validated food frequency questionnaire. Based on the questionnaire, we calculated 3 plant-based diet indices: overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI). The PDI assigned higher scores for higher consumption of all plant foods. The hPDI assigned higher scores for higher consumption of only healthy plant foods. The uPDI assigned higher scores for higher consumption of only unhealthy plant foods.

During a total of 1,191,426 person-years of follow-up, we ascertained 3074 deaths, including 447 deaths from cardiovascular disease and 1515 deaths from cancer. Comparing the highest versus lowest quintiles of PDI, the multivariable-adjusted hazard ratios of total mortality were 0.76 (95% CI, 0.68-0.85, P-trend<0.0001). Comparing the highest versus lowest quintile of uPDI, the hazard ratios were 1.30 for total mortality (95% CI, 1.15-1.48, P-trend<0.0001), 1.55 for cardiovascular disease mortality (95% CI, 1.08-2.25, P-trend = 0.06), and 1.23 for cancer mortality (95% CI, 1.02-1.47, P-trend = 0.06) after adjustment for demographic characteristics and lifestyle factors. For 10-point higher in PDI score was associated with 13% (95% CI, 0.82-0.92, P < 0.0001) lower risk of total mortality. In contrast, 10-point higher in uPDI score was associated with 16% (95% CI, 1.06-1.17, P < 0.0001) higher risk of total mortality with modest association with cancer mortality. No association was observed between hPDI and any cause of mortality. The correlation coefficients were 0.39 between PDI and hPDI, -0.22 between hPDI and uPDI, and 0.07 between PDI and uPDI.

Overall, greater adherence to a plant-based dietary pattern was associated with lower total mortality, but among those with predominantly unhealthful plant-based diets, total and disease-specific mortality rates were higher. The quality of plant foods may be crucial for reducing mortality in a population that mainly consume diets rich in plant foods.