Dietary (Poly)phenols and Cognitive Decline: A Systematic Review and Meta-Analysis of Observational Studies

ScopeThis study aims to systematically review observational studies investigating the relation between dietary (poly)phenol consumption and various cognitive outcomes.Methods and resultsEmbase and PubMed databases are searched from inception to April 2023 for observational studies investigating the relation between dietary (poly)phenol intake and cognitive outcomes. For quantitative analyses, random effects models, subgroup analyses, and dose-response analyses are performed. A total of 37 studies are included in the systematic review. Among (poly)phenols, a higher intake of flavonoids is associated with better cognitive function and lower odds of cognitive decline (although with some exceptions). A quantitative meta-analysis shows an overall inverse association with cognitive impairment and reduced association with the incidence of dementia or related disorders for total flavonoids (relative risk (RR) = 0.83, 95% confidence interval (CI): 0.76, 0.89), anthocyanins (RR = 0.73, 95% CI: 0.60, 0.89), flavones (RR = 0.77, 95% CI: 0.63, 0.94), flavan-3-ols (RR = 0.86, 95% CI: 0.82, 0.91), and flavonols (RR = 0.88, 95% CI: 0.80, 0.96). Data on other (poly)phenolic compounds (i.e., phenolic acids) are promising but too preliminary.ConclusionHabitual inclusion of flavonoids in the diet may play a preventive role against cognitive disorders. Increasing evidence suggests a plausible role of dietary (poly)phenols in the prevention of chronic diseases. This meta-analysis of observational studies shows an inverse association between total flavonoid, anthocyanin, flavone, flavan-3-ol, and flavonol intakes and cognitive impairment and dementia. Higher flavonoid intakes may be inversely associated with cognitive impairment and dementia. image