Most People with This Common Disease Are Unaware

About 1.8 million Americans have celiac disease, but around 1.4 million of them don't know they have it, according to a new estimate.

The study confirms researchers' suspicions that most cases of celiac disease — a digestive disorder in which the body can't break down foods containing gluten like wheat, rye and barley — are going undetected.

"This provides proof that this disease is common in the United States," lead researcher Joseph Murray, a Mayo Clinic gastroenterologist, said in a statement. "If you detect one person for every five or six (who have it), we aren't doing a very good job detecting celiac disease."

At the same time, 1.6 million Americans are on a gluten-free diet, which is used to treat celiac disease, even though they haven't been diagnosed with the disorder, the study found.

"There are a lot of people on a gluten-free diet, and it's not clear what the medical need for that is," Murray said in a statement. "It is important if someone thinks they might have celiac disease that they be tested first before they go on the diet."

Symptoms of celiac disease include diarrhea, stomach cramps and intestinal bloating. If left untreated, the disease can hinder the body's ability to absorb nutrients and lead to medical complications. Though the autoimmune disease was thought to develop in childhood, research published in 2010 suggested its incidence grows as the population ages. The findings, detailed in the journal Annals of Medicine, suggest  environmental factors may play a role in the development of the disease — and that the disease could possibly be prevented.

And if not prevented, the disease could be treated with certain therapies, though no "cure" has been found. For instance, research published in 2010 in the journal Science Translational Medicine, found that three chemical fragments within the gluten protein trigger the body's immune system to go haywire when a person with celiac eats a gluten-containing food. Exposing patients to small amounts of the three peptides may allow them to better tolerate gluten, the study researchers noted in 2010.

The Mayo Clinic study, which was published online July 31 in the American Journal of Gastroenterology, was based on blood tests on 7,798 individuals ages 6 and older who participated in the National Health and Nutrition Examination Survey from 2009 to 2010. Scientists also conducted interviews with the participants. Evidence of celiac disease was found in 35 participants, 29 of whom were unaware of their diagnosis.

Follow LiveScience on Twitter @livescience. We're also on Facebook & Google+.