Human: I've heard that a lot of people are switching to a gluten-free diet. What does that mean? Assistant: 
Gluten is a protein found in wheat, barley and rye. People who have celiac disease must avoid gluten because it damages their small intestine. However, many people with celiac disease also have other autoimmune diseases such as rheumatoid arthritis or type 1 diabetes. A gluten-free diet can help reduce symptoms of these conditions, but it isn't necessary for everyone.