What is gluten? The short answer
Gluten is a protein found in grains including wheat, rye and barley. It forms a sort of sticky “glue” — thus the name — and helps give many baked goods their airy structure.
See below for longer answers and more information.
Two plant proteins — gliadin and glutenin — found in some grains, bond together and form gluten when combined with water. Gluten occurs naturally in wheat, rye, barley, and crossbreeds of these grains. Foods that typically contain gluten include breads, cakes, cereals, pastas, and many other foods. Gluten is the ingredient that gives breads and other grain products their shape, strength, and texture.
Gluten proteins play a key role in determining the unique baking quality of wheat by conferring water absorption capacity, cohesivity, viscosity and elasticity on dough.
The wheat gluten proteins correspond to the major storage proteins that are deposited in the starchy endosperm cells of the developing grain. These form a continuous proteinaceous matrix in the cells of the mature dry grain and are brought together to form a continuous viscoelastic network when flour is mixed with water to form dough. These viscoelastic properties underpin the utilization of wheat to give bread and other processed foods. One group of gluten proteins, the HMM subunits of glutenin, is particularly important in conferring high levels of elasticity (i.e. dough strength). These proteins are present in HMM polymers that are stabilized by disulphide bonds and are considered to form the ‘elastic backbone’ of gluten.
Gluten proteins can be divided into two main fractions according to their solubility in aqueous alcohols: the soluble gliadins and the insoluble glutenins. Both fractions consist of numerous, partially closely related protein components characterized by high glutamine and proline contents.
Why people avoid gluten
Gluten can be harmful to people with celiac disease, an inherited chronic inflammatory auto-immune disorder that is estimated to affect up to 3 million Americans. For people who have celiac disease, consumption of gluten results in the destruction of the lining of the small intestine and the risk of other serious health conditions.
In people with celiac disease, foods that contain gluten trigger production of antibodies that attack and damage the lining of the small intestine. Such damage limits the ability of celiac disease patients to absorb nutrients and puts them at risk of other very serious health problems, including nutritional deficiencies, osteoporosis, growth retardation, infertility, miscarriages, short stature, and intestinal cancers.
Non-Celiac Gluten sensitivity (NCGS) was originally described in the 1980s and recently a “re-discovered” disorder characterized by intestinal and extra-intestinal symptoms related to the ingestion of gluten-containing food, in subjects that are not affected with either celiac disease (CD) or wheat allergy (WA).
Sources: US Food and Drug Administration – Gluten-Free Labeling of Foods; Food Microbiology – Chemistry of gluten proteins, 2007 Apr;24(2):115-9; Nutrients – Non-Celiac Gluten sensitivity: the new frontier of gluten related disorders, 2013 Sep 26;5(10):3839-53. doi: 10.3390/nu5103839.