Tea, Coffee and Health Benefits

Abstract

A number of epidemiological studies and clinical trials have reported the beneficial effects of both green tea and coffee on human health, including anticancer, anti-obesity, antidiabetic, antihypertensive, and hepatoprotective effects. Furthermore, these findings in humans are supported by cell-based and animal experiments. These effects have been attributed to epigallocatechin gallate (EGCG) in green tea and chlorogenic acid (CGA) in coffee, which have been proposed to function via various mechanisms of action, the most important of which appears to implicate reactive oxygen species (ROS). Both EGCG and CGA can exert conflicting dual actions as an antioxidant and a prooxidant. Their antioxidative action can scavenge ROS, leading to downregulation of nuclear factor-κB to produce various favorable effects such as anti-inflammatory effects and cancer cell apoptosis. The prooxidant actions, however, can promote the generation of ROS leading to the activation of 5’AMP-dependent protein kinase, which modulates various enzymes and factors with beneficial roles. At present, it remains unclear how EGCG and CGA can be directed to act as either a prooxidant or an antioxidant, although their cellular concentrations, the presence of metal cations such as Cu+ and Fe++, and the redox state of the cells appear to be important factors. Notably, several human studies did not report the beneficial health effects of green tea and coffee. The inconsistent results may have been caused by various confounding factors including smoking, intestinal microbiota, and genetic factors. This chapter examines the current information on these properties of green tea and coffee with the aim of improving the understanding of a way to enjoy healthy longevity.