A healthful plant-based diet is associated with lower type 2 diabetes risk via improved metabolic state and organ function: A prospective cohort study

Background: Plant-based diets are becoming increasingly popular due to favourable environmental footprints and have been associated with lower risk of type 2 diabetes mellitus (T2DM). Here, we investigated the potential mechanisms to explain the lower T2DM risk observed among individuals following plant-based diets. Methods: Prospective data from the UK Biobank, a cohort study of participants aged 40 to 69 years at baseline, was evaluated. Associations between healthful and unhealthful plant-based indices (hPDI and uPDI) and T2DM risk were analysed by multivariable Cox regression models, followed by causal mediation analyses to investigate which cardiometabolic risk factors explained the observed associations. Results: Of 113,097 study participants 2,628 developed T2DM over 12 years of follow-up. Participants with the highest hPDI scores (Quartile 4) had a 24 % lower T2DM risk compared to those with the lowest scores (Quartile 1) [Hazard Ratio (HR): 0.76, 95 % Confidence Interval (CI): 0.68-0.85]. This association was mediated by a lower BMI (proportion mediated: 28 %), lower waist circumference (28 %), and lower concentrations of HBA1c (11 %), triglycerides (9 %), alanine aminotransferase (5 %), gamma glutamyl transferase (4 %), C-reactive protein (4 %), insulin-like growth factor 1 (4 %), cystatin C (4 %) and urate (4 %). Higher uPDI scores were associated with a 37 % higher T2DM risk [HR: 1.37, 95 % CI:1.22- 1.53], with higher waist circumference (proportion mediated: 17 %), BMI (7 %), and higher concentrations of triglycerides (13 %) potentially playing mediating roles. Conclusion: Healthful plant-based diets may protect against T2DM via lower body fatness, but also via normoglycaemia, lower basal inflammation as well as improved kidney and liver function.