Quality of plant-based diet and the risk of dementia and depression among middle-aged and older population

several previous studies have shown the importance of the plant-based diets. However, not all plant-based foods are necessarily beneficial for dementia or depression. This study aimed to prospectively investigate the association between an overall plant-based diet and the incidence of dementia or depression.we included 180,532 participants from the UK Biobank cohort study, free of a history of cardiovascular disease, cancer, dementia and depression at baseline. We calculated an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI) and an unhealthful plant-based diet index (uPDI) based on 17 major food groups from Oxford WebQ. Dementia and depression were evaluated using hospital inpatient records in UK Biobank. Cox proportional hazards regression models were used to estimate the association between PDIs and the incidence of dementia or depression.during the follow-up, 1,428 dementia cases and 6,781 depression cases were documented. After adjusting for several potential confounders and comparing the highest with the lowest quintile of three plant-based diet indices, the multivariable hazard ratios (95% confidence intervals (CIs)) for dementia were 1.03 (0.87, 1.23) for PDI, 0.82 (0.68, 0.98) for hPDI and 1.29 (1.08, 1.53) for uPDI. The hazard ratios (95% CI) for depression were 1.06 (0.98, 1.14) for PDI, 0.92 (0.85, 0.99) for hPDI and 1.15 (1.07, 1.24) for uPDI.a plant-based diet rich in healthier plant foods was associated with a lower risk of dementia and depression, whereas a plant-based diet that emphasises less-healthy plant foods was associated with a higher risk of dementia and depression.