Researchers with Columbia University’s Celiac Disease Center report that probiotic supplements labeled as gluten-free can actually contain gluten, thus harming those with celiac disease. After looking at 22 over-the-counter probiotic products, they found that 55 percent tested positive for gluten amounts above federal limits.

Celiac disease, which is genetically transmitted, triggers a dramatic immune response from the eating of certain grain products, causing pain and damaging the small intestine. This  interferes with the body’s ability to absorb nutrients, potentially leading to malnutrition and other complications. The amino acids (collectively known as gluten) which cause such problems are in wheat, rye, barley and oats.

The researchers said about one-quarter of celiac patients use supplements and that probiotics are the most frequent variety. And that such people actually experienced more symptoms then those who did not take such supplements.

The director of the center, Dr. Peter Green, said he and his staff are concerned, characterizing the situation as “a potential hazard.” One of the authors of the study asked in a press release why consumers should pay attention at all to gluten-free labeling if the products nevertheless contain gluten. Dr. Benjamin Lebwohl wondered aloud if “regulatory bodies [will] take action to protect the public?”

The U.S. Government’s Food and Drug Administration has set gluten limits at 20 parts per million but the Celiac Disease Center tests showed four brands containing more than that amount. Alarming, say the researchers, because over half the brands they tested displayed “gluten-free” on their packaging.

The study was presented May 16 at Digestive and Disease Week in Washington DC. It is the world’s largest conference of professionals in gastroenterology are related fields.