The body’s cells use oxygen to produce energy. In the process, oxygen sometimes reacts with body compounds to produce highly unstable molecules known as free radicals. In addition to normal body processes, environmental factors such as radiation, pollution, tobacco smoke, and others can act as oxidants and cause free radical formation. The trouble begins when free radicals in the body exceed its defenses against them, a condition known as oxidative stress.
To regain its stability, the free radical quickly finds a stable but vulnerable compound from which to steal an electron. With the loss of an electron, the formerly stable molecule becomes a free radical itself and steals an electron from some other nearby molecule, thus an electron snatching destructive chain reaction is set off.