Dr. John “Jack” B. Doyle is a gastroenterologist and Assistant Professor of Medicine at Columbia University Irving Medical Center, New York, NY. He specializes in the diagnosis and treatment of a variety of diseases of the gastrointestinal tract and is a faculty member in the Celiac Disease Center at Columbia University.
Featured Expert: John B. Doyle, MD| August 12, 2026
Stool color isn’t something you think about every day, but it’s something worth paying attention to, especially if you notice anything “off” with how your...
