Free radicals and antioxidants: updating a personal view.

This article looks back to the antioxidant/free radical field in 1994 and discusses how it has progressed in the past 18 years. In some areas, there has been little change: the role of oxygen radicals and other reactive oxygen species (ROS) in the origin or progression of most human diseases remains uncertain, with cancer and neurodegenerative disease being likely exceptions. Even in diseases in which ROS are involved there has been little progress in developing effective antioxidant treatments. Mega-doses of dietary antioxidants have also generally failed to prevent human disease, in part because they do not decrease oxidative damage in vivo (as revealed by robust biomarkers). However, some strategies that are known to delay disease onset may act, at least in part, by decreasing oxidative damage levels. Nevertheless, far more is known today about endogenous antioxidant defenses and how they are regulated, which has led to a deeper understanding of how some ROS can act as signaling molecules. Increasing endogenous antioxidant levels (e.g., by supplying "pro-oxidants") may be a better approach to therapeutics and disease prevention than consuming large doses of "dietary antioxidants."