Gluten is the protein component of wheat and other related grains. A significant percentage of people have some level of intolerance to the gliadin polypeptide, which comprises 50% of gluten protein. This intolerance is not an allergy but a mucotoxic autoimmune reaction that occurs as a result of the body's effort to digest the gliadin polypeptide. In gluten intolerant people, gliadin damages the topography (villi) of the small intestine.
This damage impairs the absorption of nutrients from digested food. With repeated exposure to gliadin, these villi can become shortened or completely flattened, yielding loss of absorptive surface area and capability.

Patients with overt GI symptoms recognized as being related to celiac disease: steatorrhea, GI distress, diarrhea and/or constipation, may be the lucky ones. Because they have symptoms, they are diagnosed and make appropriate dietary changes to avoid gluten. Others with sub-clinical gluten intolerance may have no overt GI symptoms but suffer ill health effects such as:
mal-absorption of nutrients, osteoporosis, osteopenia, fatigue, anemia, irritability and/or difficulty concentrating; with no clue that these general, sometimes vague symptoms are related to gluten consumption. Having undetected sub-clinical gluten intolerance can become a serious source of unseen chronic stress.