A study using frozen blood samples taken from Air Force recruits 50 years ago has found that intolerance of wheat gluten, a debilitating digestive condition, is four times more common today than it was in the 1950’s.

The findings contradict the conventional wisdom that the sharp increase in diagnoses of wheat gluten intolerance has come about because of greater awareness and detection. It now seems likely that dramatic changes in the American diet have played a role.

The disease occurs in people whose bodies cannot digest gluten, a protein found in wheat, rye and barley. The undigested protein triggers the immune system to attack the lining of the small intestine, causing diarrhea, nausea and abdominal pain.

The researchers who conducted the study also found that the recruits who had the undiagnosed digestive disorder, called celiac disease, had a four-fold increase in their risk of death.