The benefits and hazards of antioxidants: Controlling apoptosis and other protective mechanisms in cancer patients and the human population

Cellular oxidants, called reactive oxygen species (ROS), are constantly pro duced in animal and human cells. Excessive ROS can induce oxidative damage in cell constituents and promote a number of degenerative diseases and agin g. Cellular antioxidants protect against the damaging effects of ROS. Howev er, in moderate concentrations. ROS are necessary for a number of protectiv e reactions. Thus, ROS are essential mediators of antimicrobial phagocytosi s, detoxification reactions carried out by the cytochrome P-450 complex, an d apoptosis which eliminates cancerous and other life-threatening cells. Ex cessive antioxidants could dangerously interfere with these protective func tions, while temporary depletion of antioxidants can enhance anti-cancer ef fects of apoptosis. Experimental data are presented supporting these notion s. The human population is heterogeneous regarding ROS levels. Intake of ex ogenous antioxidants (vitamins E, C. beta-carotene and others) could protec t against cancer and other degenerative diseases in people with innate or a cquired high levels of ROS. However, abundant antioxidants might suppress t hese protective functions. particularly in people with a low innate baselin e level of ROS. Screening human populations for ROS levels could help ident ify groups with a high level of ROS that are at a risk of developing cancer and other degenerative diseases. It also could identify groups with a low level of ROS that are at a risk of down-regulating ROS-dependent anti-cance r and other protective reactions. Screening populations could provide a sci entifically grounded application of antioxidant supplements, which could si gnificantly contribute to the nation's health.