The protective effects of polyphenols on Alzheimer's disease: A systematic review

INTRODUCTION: Foods rich in polyphenols have been positively correlated to a reduced risk of several noncommunicable diseases, including Alzheimer's disease (AD). The aim of this systematic review was to collect and evaluate all the relevant studies on the beneficial effects of polyphenols on AD. METHODS: Studies have been collected through a systematic search on two databases: PubMed and Web of Science. Both randomized controlled trials (RCTs) and observational studies with human subjects were included. RESULTS: A total of 24 studies were included in this review. Twelve studies found a positive correlation with reduced cognitive decline. Five studies did not find any correlation and seven studies reported mixed results. No conclusive evidence was found for phenolic acids and flavonoids. DISCUSSION: This systematic review did not find sufficient evidence to confirm that polyphenols have beneficial effects against AD. Further RCTs of human subjects would be necessary to complete the results drawn from this research.