Celiac disease is a digestive disorder in which the body’s immune system reacts to a protein called gluten. This reaction causes damage to the small intestine and prevents it from absorbing essential nutrients from food. The cause of celiac disease is unknown, and there is currently no cure. However, patients who adopt a gluten-free diet may greatly reduce the symptoms of this disease. According to the American Celiac Disease Foundation, gluten is most commonly found in wheat, barley and rye — and products made from those grains.