“Wheat, barley and rye also contain fructans. Fructan is a type of carbohydrate that provides food for healthy bacteria in the colon, called probiotics. Wheat is the biggest source of fructans in the food supply. When you eliminate wheat from your diet, you also eliminate this source of healthy bacteria.”
Since I could not have said the above information better, it is a direct quote from Mayo Clinic Going Gluten-Free by Murray, Joseph A., 2014.