Polyphenols and their Impact on Human Health And Performance: Plant Power

Consumption of a diet containing high quantities of fruits and vegetables are often advocated to confer health benefits such as reducing the risk of developing cardiovascular diseases, some cancers and neurodegenerative diseases. The potential benefits attributed to these foods may, at least in part, reside with their fermentable fibre content as well as polyphenol composition. Polyphenols have been shown to induce antioxidant and anti-inflammatory effects, although the precise mechanisms of action remain unclear. They are radical scavengers in vitro, but due to their relatively low concentration in biological fluids, their antioxidant properties in vivo are more likely to be related to upregulation of endogenous antioxidant systems via signalling through the Nrf2 pathway, as well as inhibition of superoxide producing enzymes such as NADPH oxidases. Anti-inflammatory properties may be mediated via inhibition of cyclo-oxygenase enzyme, although interesting evidence is also emerging of interaction with the gut microbiome to influence polyphenol bioavailability and microbial diversity.

As a consequence, there is a rationale for supplementation with fruit-derived polyphenols to support healthy aging and enhance exercise performance and recovery from muscle damage due to the role of oxidative stress and inflammation in the development of non-communicable diseases and fatigue development within skeletal muscle. Indeed, randomized controlled trials investigating the effects of acute or chronic consumption of polyphenol rich supplements have demonstrated favorable effects on health outcomes such as vascular function (via nitric oxide mediated mechanisms), cognitive function and insulin sensitivity, as well as exercise performance and recovery from muscle damage. However, there are still significant gaps in our knowledge. For instance, the optimal blend, form (concentrate, powder, whole food), dose and timing of supplementation to achieve a desired effect is not known. Our ability to extrapolate from the literature is constrained by the poor reporting of supplement composition, compounded by wide variation in the analysis methods employed. The host- and microbial-mediated mechanisms of action are still poorly understood with a reliance on the measurement of blood biomarkers of oxidative damage and inflammation in human studies, or in vitro work and animal studies.

The goal of this Research Topic is to present state-of-the-art research studies that investigate the effects of polyphenols from whole foods or supplements on human physiology, nutritional biochemistry, and/or the gut microbiome. Emphasis will be directed towards well-designed nutritional studies that provide a careful characterization of the polyphenol blend and amount provided, and their impacts on human health more broadly, as well as exercise performance, recovery and training adaptation in athletes. To that end, we encourage submission of Original Research, Reviews, Perspectives and Case Reports.