Unhealthy plant-based diet is associated with a higher cardiovascular disease risk in patients with prediabetes and diabetes: a large-scale population-based study.

Background: The role of plant-based dietary patterns in preventing cardiovascular disease (CVD) among individuals with prediabetes and diabetes remains unclear. We aimed to evaluate the associations of plant-based diet index (PDI), healthful PDI (hPDI), and unhealthful PDI (uPDI) with cardiovascular disease (CVD) risk and explore potential contributing factors among people with prediabetes and diabetes.

Methods: A total of 17,926 participants with prediabetes and 7798 with diabetes were enrolled from the UK Biobank between 2006 and 2010 and followed until the end of 2020. We calculated the PDI, hPDI, and uPDI based on 18 major food groups including plant-based foods and animal-based foods and applied Cox proportional hazard models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for CVD risk related to PDI, hPDI, and uPDI. Decomposition analysis was performed to assess the role of dietary components, and mediation analysis was performed to assess the potential mediating role of serum biomarkers underlying these associations.

Results: A total of 2324 CVD events were documented among individuals with prediabetes, while 1461 events occurred among patients with diabetes. An inverse association was found between hPDI and CVD risk among individuals with prediabetes (HR T3 vs. T1 = 0.88, 95% CI = 0.79-0.98, P_trend = 0.025) but not those with diabetes. A positive association was found between uPDI and CVD risk among individuals with prediabetes (HR T3 vs. T1 = 1.17, 95% CI = 1.05-1.30, P_trend = 0.005) and those with diabetes (HR T3 vs. T1 = 1.14, 95% CI = 1.00-1.29, P_trend = 0.043). High-sugar-sweetened beverages (SSB) intake accounted for 35% of the hPDI-CVD association and 15% of the uPDI-CVD association among individuals with prediabetes, whereas low intake of whole grain accounted for 36% of the association among patients with diabetes. Elevated cystatin C levels explained the largest proportion of the association between uPDI and CVD risk among individuals with prediabetes (15%, 95% CI = 7-30%) and diabetes (44%, 95% CI = 9-86%).

Conclusions: Adherence to an unhealthy plant-based diet is associated with a higher CVD risk in people with prediabetes or diabetes, which may be partially attributed to low consumption of whole grains, high intake of SSB, and high blood cystatin C levels.