A gluten-free diet is a diet that excludes foods that have gluten. Gluten is a protein found in wheat, barley, rye, and possibly oats. Most breads, cakes, pastas/noodles, beers and pizzas are made with gluten. Gluten is used as a food additive in the form of a flavoring, stabilizing or thickening agent. It is often called "dextrin". Some non-foods, such as medications and vitamin supplements, especially those in tablet form, may contain gluten as a binding agent.