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Study Finds Many Probiotics Are Contaminated with Traces of Gluten

More than half of popular probiotics contain traces of gluten, according to an analysis performed by investigators at the Celiac Disease Center at Columbia University Medical Center (CUMC). Tests on 22 top-selling probiotics revealed that 12 of them (or 55%) had detectable gluten.

Probiotics are commonly taken by patients for their theoretical effect in promoting gut health, though evidence of benefits is limited to a few clinical situations. "Many patients with celiac disease take dietary supplements, and probiotics are particularly popular," says Samantha Nazareth, MD, a gastroenterologist at CUMC and the first author of the study. "We've previously reported that celiac patients who use dietary supplements have more symptoms than non-users, so we decided to test the probiotics for gluten contamination," Nazareth says.

Gluten is a protein found in wheat, rye, and barley, and patients with celiac disease need to eliminate it from their diet or face pain, bowel symptoms, and an increased risk of cancer. The investigators used liquid chromatography-mass spectrometry, a sensitive detection technology, to quantify gluten content. Most of the probiotics that tested positive for gluten contained less than 20 parts per million of the protein, and would be considered gluten-free by Food and Drug Administration (FDA) standards. However, four of the brands (18% of the total) contained in excess of that amount.

More than half of the 22 probiotics were labeled gluten-free, but this had no bearing on whether or not traces of gluten were present. Two probiotics that didn't meet FDA standards carried the label. "We've been following reports in the scientific literature and news media on inaccurate labeling of nutritional supplements, and it appears that labels claiming a product is gluten-free aren't to be trusted, at least when it comes to probiotics," says Peter Green, MD, professor of medicine and director of the Celiac Disease Center. "This is a potential hazard for patients, and we're concerned."

It's uncertain whether these trace amounts of gluten could cause symptoms or otherwise harm patients with celiac disease. "We know that most patients with celiac disease only develop intestinal damage when consuming more than 10 mg of gluten daily, and it's unlikely that contaminated probiotics can lead to that amount unless patients are ingesting mega-doses," says Benjamin Lebwohl, MD, assistant professor of medicine and epidemiology at the Celiac Disease Center and a co-author of the study.

Still, these findings raise troubling questions, Lebwohl says. "Why is there any gluten in these products? Why should the consumer pay any attention to gluten-free labeling on such products? And given the great consumer interest in probiotics, will regulatory bodies take action to protect the public?"

--Source: Columbia University Medical Center