Celiac disease—an allergic immune response to gluten, a mix of proteins found in most grains and wheat breads—is now more than four times more common among Americans than it was 50 years ago, with nearly 1 percent of the population affected, Time.com reports.

Now, two new studies published in the New England Journal of Medicine have further complicated scientists’ hypotheses on why there’s been such a rise in the autoimmune disease. The findings also further thwarted efforts toward finding a cure.

One Italian study looked into whether the age at which gluten was introduced into a person’s diet could affect his or her likelihood of developing an intolerance to the substance. After keeping gluten away from newborns for one year, researchers found no difference in celiac prevalence among those in the group that underwent delayed exposure.

The second study included almost 1,000 children who were genetically pre-disposed to the disease. For this research, scientists slowly introduced gluten into the diets of breast-feeding babies to see if that would help improve their tolerance. That study also showed no difference in disease incidence.

Joseph A. Murray, MD, a professor of medicine and gastroenterologist at the Mayo Clinic, said that although both studies were expertly designed and executed, each trial was “a spectacular failure” in the search for a celiac cure.

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