Intestinal absorption and bioavailability of coffee phenolics and green tea polyphenols: a study in healthy and ileostomy volunteers

Flavonoids and phenolic compounds (aka polyphenols) are phytochemicals, thought to participate in plant development and defence mechanisms. Polyphenols are ubiquitous plant secondary metabolites, and are usually found conjugated as glycosides or esters. These compounds have been of particular interest as part of the human diet, and have been the focus os many studies in nutrition research. Many epidemological studies have found a correlation between flavonoid intake and protection against certain chronic diseases such as cancer and cardiovascular events. The mechanisms underlying such benefits, however, remain to be unveiled, as judged by the number of in vitro and animal model intervention studies. The primary property attributed to polyphenolic and phenolic compounds relates to their antioxidant activities. Outcome from in vitro studies have established the ability of polyphenols to scavenge radical species and bind to metal ions, thus preventing the damage caused by oxidative stress. Recent progress in the field has broadened the knowledge of how polyphenols exert their beneficial effects, which appears to depend on more than simply antioxidant activity. Indeed, polyphenols are thought to actively participate in the modulatory effects involved in signal transduction in cells, responsible for the regulation of genes, apoptosis and cell proliferation