Celiac disease is the reason why so many people can’t eat bread. The disease is really an autoimmune disorder, meaning every time a patient consumes gluten — a common protein found in wheat, rye, and barley — their immune system attacks the lining of the small intestine; painful digestive problems ensue. But across the country, roughly 3 million Americans claim to have a similar insensitivity without a proper diagnosis. So, a team of researchers from Columbia University Medical Center (CUMC) decided to find out why.