Gluten and gliadins are present in all wheat grains and can induce celiac disease in genetically susceptible individuals. Analysis of ancient (often referred to European wheats) and modern wheats show that the protein content of modern bread wheat (Triticum aestivum) has decreased over time while the starch content increased. In addition, it was shown that compared to bread wheat, ancient wheats contain more protein and gluten. Gliadins and the glutenins are the two main components of the gluten fraction of all wheat seed. North America grows more hard red wheat which is higher in gluten. More information can be read here.