Plant-based diet quality, fat mass, and cardiovascular disease: A mediation analysis of mid-aged adults in the UK Biobank.

Abstract

Evidence supports plant-based diets for preventing cardiovascular diseases (CVD). Fat mass is a strong predictor of CVD, however it is unclear whether this mediates the relationship between plant-based diets and CVD. Thus, this study aimed to determine if longitudinal associations between plant-based diet quality indices and incidence of CVD events, CVD mortality and all-cause mortality were mediated by fat mass in mid-aged adults. Dietary data (Oxford WebQ) from 14,233 adults from the UK Biobank were used to calculate adherence to three plant-based diet quality indices: an overall plant-based diet (PDI), a healthy plant-based diet (hPDI), and a less healthy plant-based diet (uPDI). Dual X-ray absorptiometry measured percentage fat mass. Cox proportional hazard ratios (95% CI) identified associations between the indices and CVD events, CVD mortality or all-cause mortality, and mediation analyses determined overall, direct, and indirect effects of fat mass. The PDI and hPDI were inversely associated with fat mass, and the uPDI was positively associated (p < 0.001). In several models, fat mass was associated with CVD events, CVD mortality, and all-cause mortality after controlling for the plant-based diet quality indices. No association was found between the indices and health outcomes, with (direct effect) or without (total effect) the fat mass mediator (p ≥ 0.1). In several models there was a significant negative indirect effect for the PDI or hPDI on CVD events or CVD mortality via the fat mass mediator, and a significant positive indirect effect for the uPDI on CVD events and CVD mortality. No evidence was found for an association between the plant-based diet quality indices on the outcomes without, as well as after accounting for fat mass. However, the significant indirect effects found suggest that fat mass may be a key mechanism linking plant-based diets to CVD.