Beneficial effects of polyphenols on neurodegenerative diseases

In this paper, the authors state that “Several epidemiological studies and clinical trials have reported the beneficial effects of green tea, coffee, wine, and curry on human health, with its anti-obesity, anti-cancer, anti-diabetic, and neuro-protective properties. These effects, which have been supported using cell-based and animal studies, are mainly attributed to epigallocatechin gallate found in green tea, chlorogenic acid in coffee, resveratrol in wine, and curcumin in curry”.
“Polyphenols are proposed to function via various mechanisms, the most important of which is related to reactive oxygen species (ROS). These polyphenols exert conflicting dual actions as anti- and pro-oxidants. Their anti-oxidative actions help scavenge ROS and downregulate nuclear factor-κB to produce favourable anti-inflammatory effects. Meanwhile, pro-oxidant actions appear to promote ROS generation leading to the activation of 5’-AMP-activated protein kinase, which modulates different enzymes and factors with health beneficial roles. Currently, it remains unclear how these polyphenols exert either pro- or anti-oxidant effects”.
In their review, the authors summarise the favourable anti-obesity effects of consuming green tea, coffee, wine, and curry and their principal associated polyphenols. They state that while considerable human observational and intervention studies have expounded this hypothesis, several studies have failed to show any beneficial effects. Such differences may have been due to confounding factors, e.g., differences in study design, quantifying consumption methods, beverage temperatures, cigarette smoking, alcohol consumption, and differences in genetic and environmental factors, such as race, sex, age, lifestyle, intestinal microbiota, and genetic polymorphisms. Further complicating these issues is the fact that polyphenols have limited bioavailability as their absorption from the human digestive system is restricted; thus, they are predominantly metabolised in the gut and liver. The authors argue that in the future, more comprehensive and definitive human studies should be performed to assess the bioavailability of polyphenols and prove the anti-obesity effects of consuming these foods.
Source: Ohishi, T.; Fukutomi, R.; Shoji, Y.; Goto, S.; Isemura, M. The Beneficial Effects of Principal Polyphenols from Green Tea, Coffee, Wine, and Curry on Obesity. Molecules 2021, 26, 453.