The theory suggests that very reactive chemicals, called "free radicals," can be damaging to the body at the cellular level. Those reactive chemicals can take part in unnecessary chemical reactions that can damage the cell components, including DNA. Some researchers believe that free radicals could contribute to or hasten heart disease, cancer, and other age-related diseases. The theory also suggests that if the body could be protected from those free radicals, then age-related diseases could be tamed and organisms and ultimately people may be able to live longer.
Scientists have previously been able to extend the lifespan of mice in lab experiments by managing their diets and reducing their caloric intake. Another method relied on the restriction of a growth factor, but a side effect was that the mice suffered from dwarfism. However, neither of those methods of elongating the mouse lifespan was clearly connected to the free-radical theory of aging.
A group of scientists led by Dr. Peter Rabinovitch, professor of pathology at the UW School of Medicine, examined a method that was closely connected to the free-radical theory. He and his colleagues focused their study on catalase, an enzyme in the body that helps convert hydrogen peroxide into water and oxygen. Hydrogen peroxide is a waste product of metabolism and it can be a the precursor of free radicals that can damage the cell. The damage can in turn lead to more flaws in the cell's chemical processes, making a vicious cycle that leads to more free radicals, more cellular damage, and so on.