The free radical theory of aging suggests that accumulation of oxidative damage caused by free radicals is a major contributor to the aging process. Free radicals are highly reactive molecules that can damage cells and their components, including DNA, proteins, and lipids. Over time, this damage can lead to cellular dysfunction and age-related diseases. According to this theory, the body's antioxidant defense mechanisms, which neutralize free radicals, become less efficient with age, resulting in an increase in oxidative damage and accelerated aging.