Most of us know that the majority of our cellular energy is manufactured within mitochondria which are organelles that dwell inside our cells. The problem is when we produce energy, a byproduct of that process creates reactive oxygen species (ROS). These ROS - or free radicals - can cause cellular damage and so for a long time a prevailing idea was that it's good to take antioxidants, like for example vitamin E, C, A, to quench these ROS signals. Turns out, that's not that case. We need these ROS signals to trigger cellular protective mechanisms. In fact, it's these ROS signals that might just be the common pathway by which many behaviors and substances exert their health-promoting effects. In this episode, Dan speaks with Professor Michael Ristow, a key player who helped turn the oxidative theory of aging on its head.