"I think if I stop being controversial I wouldn't be doing my job... I'm interested in things that don't fit established conceptions... that don't fit accepted models, and in trying to determine what's true and useful." Andrew Weil's first public controversy came when he was still a student at Harvard Medical School in 1968. His laboratory study of the effects of marijuana in human subjects was the first of its kind. The Medical School would not permit him to perform the research on campus; he was forced to use the facilities of nearby Boston University instead. His conclusions, published in Science while he was still an intern, were widely condemned. Dr. Weil continued on his own path, traveling widely to collect information on drug use in other cultures, on medicinal plants, and on alternative methods of treating disease. At the University of Arizona medical school, he has led the first effort to change medical education to include information on alternative therapies, mind/body interactions, natural healing, and other subjects not usually emphasized in the training of physicians. He has brought his findings to the general public through seven books, including the international bestsellers, Spontaneous Healing, and Eight Weeks to Optimum Health. A frequent lecturer and guest on talk shows, Dr. Weil is an internationally recognized expert on drugs and addiction, medicinal plants, alternative medicine, and the reform of medical education. In this podcast, recorded at the Auberge du Soleil in California's Napa Valley during the 2014 International Achievement Summit, Dr. Weil discusses intestinal health as the key to a functioning immune system and weighs the relative merits of fermented foods and probiotics.