Background: Polyphenols are proposed as protective factors against the occurrence of degenerative diseases affecting several systems, such as cardiovascular and neurocognitive ones. The beneficial effect of polyphenol-enriched diets is assumed to be multifactorial, including direct antioxidant and anti-inflammatory properties, as well as the polyphenol-related capability to modulate lipid metabolism and gut microbiota function. However, the prediction of polyphenols impact on human health remains uncertain, since available long-term studies provide controversial results.
Aim of the study: This meta-analysis was designed to assess the effect of polyphenols as food supplement or isolated compound on cardiovascular and neurocognitive parameters, to clarify their beneficial properties on human health.
Methods: Two literature searches were conducted to identify double-blind, randomized, controlled clinical trials published in English language until November 2018 and evaluating chronic polyphenols administration with a treatment period over 2 weeks on both cardiovascular health (search 1) and neurocognitive function (search 2). All available polyphenol-enriched compounds were considered eligible.
Results: High heterogeneity has been found in both literature searches, in terms of treatment formulation, dose, source and compounds evaluated. Thirty-four studies were included in the first analysis, evaluating cardiovascular health parameters. Polyphenols administration reduced both systolic (−1.01 mmHg, 95%CI: −2.04;0.02, P=0.005) and diastolic (−1.32 mmHg, 95%CI: −2.37; −0.27, P=0.001) pressure, as well as low-density-lipoprotein cholesterol levels (−4.39 mg/dl, 95%CI:−7.66; −1.11, P=0.009). On the contrary, the polyphenols assumption significantly increased high-density lipoprotein cholesterol serum levels (2.68 mg/dl, 95%CI: 2.43;2.92, P<0.001) and brachial artery flow mediated dilation (0.89%, 95%CI:0.40;1.38, P<0.001). Twenty-one trials were analysed in the search 2, with a great heterogeneity in neurocognitive outcomes, mostly measured with questionnaires. Although few specific neurocognitive domains, such as visual attention, immediate memory and learning, seemed to benefit from the polyphenols administration, global cognitive functions resulted not significantly improved.
Conclusion: The overall analysis revealed a significant effect of polyphenols in modulating positively the cardiovascular health parameters. Although definitive recommendations for the use of these compounds in the prevention of cardiovascular disease and cognitive decline are currently not applicable, a potential role of polyphenol compounds for diseases prevention is clearly evident, at least in the cardiovascular setting.
18 - 21 May 2019
European Society of Endocrinology