How does the mitochondrial theory explain aging?

The mitochondrial theory of aging posits that aging is driven by a self-perpetuating cycle of damage within mitochondria, the organelles responsible for cellular energy production.1

This theory suggests that reactive oxygen species (ROS)—highly reactive molecules produced as by-products of cellular respiration—damage mitochondrial DNA and proteins within the electron transport chain. Because mitochondrial DNA lacks robust repair mechanisms, these mutations accumulate over time. This damage impairs the organelle's respiration machinery, leading to further electron leakage and increased ROS production.123

This "vicious cycle" results in a progressive decline in bioenergetic efficiency, meaning mitochondria fail to produce sufficient adenosine triphosphate (ATP) for cells to function. The resulting cellular dysfunction contributes to tissue degeneration and various age-associated pathologies. While this theory provides a framework for understanding how oxidative stress impacts longevity, it is important to note that evidence regarding the specific role of mitochondrial dysfunction in normal human aging remains inconclusive.134