Many probiotics could actually be harmful: StudyWashington, May 17 (AZINS) If you believe that probiotics are good for your health, there is a piece of news for you. A new study finds that more than half of popular probiotics contain traces of gluten.

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.

Tests on 22 top-selling probiotics done by investigators at the Columbia University Medical Centre (CUMC) revealed that 12 of them (or 55 percent) had detectable gluten.

Probiotics are commonly taken by patients for their reported effect in promoting gut health.

"Many patients with celiac disease take dietary supplements and probiotics are particularly popular," said Samantha Nazareth, 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, Nazareth said.

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 percent 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.

"It appears that labels claiming a product is gluten-free are not to be trusted, at least when it comes to probiotics," said study co-author Peter Green.

"This is a potential hazard for our patients and we are concerned," he added.

"We know that most patients with celiac disease only develop intestinal damage when consuming more than 10 milligrams of gluten daily. Still, these findings raise troubling questions," said study co-author Benjamin Lebwohl from CUMC.

The study was presented at Digestive and Disease Week in Washington DC recently.