Plant-Based Dietary Patterns and Cardiometabolic Risk: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

Abstract

Objectives: Plant-based diets defined by limited animal food consumption have been extensively associated with cardiometabolic health benefits in Western nations. Diet indices are increasingly used to distinguish the protective characteristics of a plant-based diet at different levels of adherence. We aimed to synthesize evidence on the association between adherence to plant-based diet indices and cardiometabolic risk. A plant-based diet index (PDI) is hypothesized to be inversely associated with type 2 diabetes (T2D) and cardiovascular disease (CVD) with a stronger association with the healthful index (hPDI) that emphasizes higher quality plant-based foods. Methods: We systematically searched MEDLINE, EMBASE and CINAHL databases through January 2021. Prospective cohort studies assessing the association of plant-based diet indices with T2D and CVD in adults were included and appraised for risk of bias and quality (NutriGrade). We followed the PRISMA-P, Cochrane and MOOSE guidelines. Random and fixed-effects meta-analyses were conducted to pool risk ratios (RR) of extreme quantiles. Dose-response meta-analyses were conducted after harmonizing all diet index scores. I 2-values of 30-60%, 50-90%, and 75-100% denoted moderate, substantial, and considerable heterogeneity respectively. Results: We included a total of 10 studies from 5927 retrievals. Across 6 studies there were 22 135 cases of T2D over 4 817 308 person-years. Across 7 studies there were 15 077 cases of CVD over 6 117 016 person-years. The PDI was associated with a lower risk of T2D (RR = 0.82, 95% CI [0.75, 0.91], I 2 = 55.4%), and CVD (RR = 0.88, 95% CI [0.8, 0.96], I 2 = 16.2%). The hPDI had a stronger inverse association with T2D (RR = 0.73, 95% CI [0.68, 0.77], I 2 = 84.3%) and CVD (RR = 0.8, 95% CI [0.77, 0.88], I 2 = 55.9%). All dose-response relationships were linear (except hPDI with CVD). All studies had acceptable risk of bias and the quality of evidence was moderate. Conclusions: Adherence to a plant-based diet was inversely associated with T2D and CVD with a stronger association for a healthful plant-based diet pattern. Since highest quantiles of the index still included moderate meat consumption, linear dose-responses emphasized potential benefits on risk of T2D and CVD with any incremental progression towards a plant-based diet.