Gluten is a protein found in wheat and some other grains that become tough and elastic when worked in water, providing strength and structure to baked goods. Pizza and bread crusts rely on gluten for their distinctive textures. Those who suffer from celiac disease are sensitive to gluten in foods.
Gluten is a necessary part of most baked goods because it gives the dough the elasticity it needs to hang on to carbon dioxide bubbles created by yeast. Without gluten, the gas simply escapes the batter and leaves it flat and lifeless. Over-working gluten, on the other hand, can produce a tough, inelastic dough that bakes into a hard and unappetizing final product. For this reason, recipes for baked goods often contain specific directions for working and resting the dough.
In a small percentage of the population, gluten triggers an autoimmune response in the body. This can cause diarrhea, pain and fatigue, and over the long term, damage to the intestines. Those who suffer from celiac disease must avoid most wheat-based products, choosing gluten-free baked goods such as bread made with tapioca flour. Gluten-free diets may contain deficiencies in important nutrients, however, and should only be adopted on the advice of a physician.