Which components of the Mediterranean diet are associated with dementia? A UK Biobank cohort study

Cohort studies suggest that the Mediterranean diet is associated with better global cognition in older adults, slower cognitive decline and lower risk of dementia. However, little is known about the relative contribution of each component of the Mediterranean diet to dementia risk or whether the diet's effects are due to one or more specific food components. We aimed to examine whether Mediterranean diet components are associated with all-cause dementia risk in the UK BioBank cohort. Participants joined the UK Biobank study from 2006 to 2010 and were followed until December 2020. 249,511 participants, who were at least 55 years old, without dementia at baseline were included. We used self-reported consumption of food groups, considered part of the Mediterranean diet including fruit, vegetables, processed meat, unprocessed red meat and unprocessed poultry, fish, cheese, wholegrains. Incident dementia was ascertained through electronic linkage to primary care records, hospital and mortality records or self-report. In this study with a total follow-up of 2,868,824 person-years (median 11.4), after adjusting for all covariates and other food groups, moderate fish consumption of between 2.0 and 3.9 times a week was associated with decreased risk of dementia (HR 0.84, 95%CI 0.71-0.98) compared to no consumption. Additionally, fruit consumption of between 1.0 and 1.9 servings a day was associated with reduced dementia risk (HR 0.85, 95%CI 0.74-0.99) compared to no consumption. No other Mediterranean diet components were associated with dementia risk suggesting that fish consumption may drive the beneficial effects seen from the Mediterranean diet. Further study of potential mechanisms and diet-based intervention trials are needed to establish this.