Celiac disease (pronounced SEE-lee-ack) is a medical condition where eating gluten causes the body's immune system to attack the small intestine. Gluten is a protein found in wheat, barley, and rye, which means it's in most breads, pastas, cereals, and baked goods.

When someone with celiac disease eats gluten, their body treats it like a dangerous invader and launches an attack. Unfortunately, this attack damages the lining of the small intestine, which makes it harder for the body to absorb nutrients from food. This can cause stomach pain, fatigue, and other health problems.

People with celiac disease must follow a gluten-free diet for their entire lives. This means carefully checking food labels and avoiding foods with wheat, barley, or rye. Fortunately, many foods are naturally gluten-free: rice, corn, potatoes, fruits, vegetables, meat, and dairy products. Today, grocery stores also carry gluten-free versions of bread, pasta, and other products.

Celiac disease is not the same as a wheat allergy or gluten sensitivity, though all three conditions involve problems with gluten. About 1 in 100 people worldwide has celiac disease, and doctors can diagnose it with blood tests and other medical exams.