July 1, 2009 -- Celiac disease -- the digestive disorder treated by banning wheat and other grains containing gluten from the diet -- is four times more common in the U.S. today than it was 50 years ago, a study shows.

"We believe that only about 5% of people with celiac disease know they have it," University of Chicago Celiac Disease Center Director Stefano Guandalini, MD, tells WebMD. "Many of these people have no symptoms, but many do have symptoms that are not recognized for what they are."

Celiac disease is a digestive disorder in both children and adults. When people with celiac disease eat foods that contain gluten, an inflammatory reaction occurs that can damage the small intestine and inhibit the absorption of nutrients.

Symptoms of celiac disease can include diarrhea, abdominal discomfort, weight loss, anemia, unexplained infertility, premature osteoporosis, loss of teeth, and other health issues.