Plain language summary
Literature shows that (poly)phenols are a brain-friendly intervention that may prevent and delay age-associated decline in cognitive function. The main aim of this study was to systematically review the literature and conduct a meta-analysis of all trials investigating the acute and chronic effects of (poly)phenol-rich supplementation on cognitive functions and brain health in young and middle-aged healthy adults. This study is a systemic review and meta-analysis which included 16 studies. The pooled analysis of the acute/chronic administration (4 weeks) of (poly)phenol-rich supplementation suggests a beneficial effect on the majority of the assessed cognitive functions. These beneficial effects appear to depend on the administration type (acute or chronic) and the supplementation protocols (dose and bioavailability) with more significant effects observed following acute supplementation. Authors conclude that rich polyphenol supplementation may be highly useful as an inexpensive, long-term preventive intervention on neurodegenerative diseases and cognitive decline especially in young and middle-aged adults.
Abstract
CONTEXT Affecting older and even some younger adults, neurodegenerative disease represents a global public health concern and has been identified as a research priority. To date, most anti-aging interventions have examined older adults, but little is known about the effects of polyphenol interventions on brain-related aging processes in healthy young and middle-aged adults. OBJECTIVE This systematic review and meta-analysis aimed to evaluate the acute and chronic effects of (poly)phenol-rich diet supplementation on cognitive function and brain health in young and middle-aged adults. In July 2019, two electronic databases (PubMed and Web of Science) were used to search for relevant trials examining the effect of acute or chronic (poly)phenol-rich supplementation on cognitive function and neuroprotective measures in young and middle-aged adults (<60 years old). A total of 4303 records were screened by two researchers using the PICOS criteria. Fifteen high quality (mean PEDro score = 8.8 ± 0.58) trials with 401 total participants were included in the final analyses. Information on treatment, study design, characteristics of participants, outcomes and used tools were extracted following PRISMA guidelines. When items were shown to be sufficiently comparable, a random-effects meta-analysis was used to pool estimates across studies. Effect size (ES) and its 95% confidence interval (CI) was calculated. The meta-analysis indicated that (poly)phenol supplementation significantly increased brain-derived neurotrophic factor (ES = 3.259, p = 0.033), which was accompanied by higher performance in serial (7s) subtraction (ES = 1.467, p = 0.001) and decreases in simple reaction time (ES = -0.926, p = 0.015) and mental fatigue (ES = -3.521 p = 0.010). Data related to cognitive function were skewed towards an effect from acute compared to chronic polyphenol intervention; data related to BDNF were skewed toward an effect from higher bioavailability phenolic components. CONCLUSION This meta-analysis provides promising findings regarding the usefulness of polyphenol-rich intervention as an inexpensive approach for enhancing circulation of pro-cognitive neurotrophic factors. These beneficial effects appear to depend on the supplementation protocols. An early acute and/or chronic application of low- to high-dose phenolic components with high bioavailability rates (≥30%) at a younger age appear to provide more promising effects.
Methodological quality
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