Celiac disease -- also known as celiac sprue or gluten-sensitive enteropathy -- is a digestive and autoimmune disorder that results in damage to the lining of the small intestine when foods with gluten are eaten. Gluten is a form of protein found in some grains. The damage to the intestine makes it hard for the body to absorb nutrients, especially fat, calcium, iron, and folate.
Normally, the body's immune system is designed to protect it from foreign invaders. When people with celiac disease eat foods containing gluten, their immune system forms antibodies to gluten which then attack the intestinal lining. This causes inflammation in the intestines and damages the villi, the hair-like structures on the lining of the small intestine. Nutrients from food are normally absorbed by the villi. If the villi are damaged, the person cannot absorb nutrients properly and ends up malnourished, no matter how much he or she eats.