Most gut diseases are preventable, says Dr Saurabh Sethi, a California-based gastroenterologist trained at Harvard and Stanford. In his practice, he has performed thousands of colonoscopies and diagnosed Crohn’s, colitis, fatty liver, and colon cancer. “And after all of it, I keep coming back to the same truth: most gut disease is preventable. And most prevention starts at the grocery store,” the doctor said in a recent newsletter. Here are six foods the doctor eats every single day to keep disease at bay.