More than half of popular probiotics contain traces of gluten, meaning they have the opposite effect on certain people hoping to achieve digestive health, a new study has found.
Tests on 22 top-selling probiotics showed that 12 of them (or 55 per cent) had detectable gluten, according to an analysis performed by investigators at the Columbia University Medical Centre (CUMC).
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," said Dr Samantha Nazareth, a gastroenterologist at CUMC and the first author of the study.
"We have 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," said Nazareth.
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 per cent of the total) contained in excess of that amount.
More than half of the 22 probiotics were labelled gluten-free, but this had no bearing on whether or not traces of gluten were present. Two probiotics that did not meet FDA standards carried the label.
"We have 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 are not to be trusted, at least when it comes to probiotics," said Dr Peter Green, professor of medicine and director of the Celiac Disease Centre.
"This is a potential hazard for our patients, and we are concerned," said Green.
It is uncertain whether these trace amounts of gluten could cause symptoms or otherwise harm patients with celiac disease.
