If you’re diagnosed with gluten intolerance or celiac disease, you will then have to steer clear of gluten for life. Gluten is the protein in grain-related foods like rye, barley, and wheat. Gluten could bring about an autoimmune reaction which can incur damage in the villi found in the small intestines. If villi are destroyed, you will have a problem absorbing essential nutrients, vitamins and minerals from the food that you eat.