Dr. Robert Sapolsky is a professor of biological sciences at Stanford. He's the author of "Why Zebras Don't Get Ulcers" as well as his latest work - "Behave: The Biology of Humans at Our Best and Worst."

Dr. Kari Nadeau is a Stanford immunologist who runs the Sean N. Parker Center for Allergy & Asthma Research.

Rhonda and Joe go in depth on the damage from blows to the head during MMA, genetic risk factors for Alzheimer's disease, the role of epigenetics and overall recommendations for how to eat, sleep, exercise and supplement.