The number of people diagnosed with celiac disease continued to increase during the 2000s but leveled off in 2004.
The disease, where people's immune systems react to gluten found in wheat, rye and barley, was diagnosed in 11.1 out of every 100,000 people at the start of the study in 2000, according to a new study published in the American Journal of Gastroenterology.
That number rose to 17.3 out of every 100,000 people by 2004 and remained steady until the end of the study in 2010.
"We're finding a lot more celiac disease," said Dr. Joseph Murray, the study's senior author from the Mayo Clinic in Rochester, Minnesota.
"Some of that is probably that we're better at detecting it, but the fact that we're finding it all the time shows that there are a number of new cases."
Murray and his colleagues write that better screening can not account for all of the new cases of the disease.
"Something has changed in our environment that's driving an increased incidence of celiac disease," Murray said.
The University of Chicago Hospital estimates that celiac disease affects at least 3 million Americans, or 1 percent of the healthy average population.
If a person with celiac disease consumes gluten, the immune system overreacts and can cause diarrhea and abdominal pain, according to the Mayo Clinic.
Consumption of gluten can damage the villi of the small intestine, which help the body absorb key nutrients, leading to illness and malnutrition.
Dr. Alessio Fasano, director of the Center for Celiac Research at MassGeneral Hospital for Children in Boston, told Reuters that he agreed with the study's authors that the increase in celiac diagnoses was linked to something in the environment.
"If you lead the lifestyle of three or four generations ago, you don't see this epidemic. I do believe what we're witnessing with celiac disease is that we're changing the environment way too fast for our body to adapt to it," said Fasano, who was not involved with the study.