The Italians are foremost in researching the subject. These are people with a genetic problem with gluten. They often come from families with digestive problems. Various grains contain gluten proteins. They put elasticity into the cooked product.
Wheat has the highest gluten content of any of the grains.
We have bread two or three times a day at least - not to mention biscuits, pastries and cake. It is hard to give up. Gluten is found also in rye, oats and barley. Most processed foods contain gluten to some extent or other. It takes only a few molecules of gluten to upset the tissues of the small intestine in gluten-sensitive people.