Gluten is a composite of the proteins gliadin and glutenin. These exist, conjoined with starch, in the endosperms of some grass-related grains, notably wheat, rye, and barley. Gliadin and glutenin comprise about 80% of the protein contained in wheat seed.

The stored proteins of corn and rice are sometimes called glutens, but their proteins differ importantly from wheat gluten by lacking glutenin.

Unexpected Source of Wheat/gluten:

• stamps and envelopes
• canned broth
• imitation bacon
• veggie burgers
• soy sauce
• soy marinades
• mustard
• chewing gum
• laxatives