Study: Probiotics Frequently Contain Trace Gluten

Unfortunately, There's Little You Can Do Except Watch for Symptoms

Is there gluten in your probiotics?. Ian Hooton/Getty Images

Popular probiotics sold over-the-counter frequently contain traces of gluten, regardless of whether they're labeled "gluten-free." And two brands of probiotics specifically labeled "gluten-free" contained more than the legal limit of gluten.

That's the word from researchers at Columbia University's Celiac Disease Center, who tested 22 brands of probiotics. They found 55% of the products they tested contained gluten, including 53% of those labeled "gluten-free" and 57% of those not including such a label.

"People with celiac disease have to use caution if using supplements and over-the-counter products like probiotics," author Dr. Samantha Nazareth told me in an interview. "What we found is, it didn't really matter whether the product was gluten-free-labeled or not." The researchers' findings were presented May 16, 2015 at the Digestive Disease Week conference.

To meet the legal standard for a food or product to be labeled "gluten-free," that food or product must contain less than 20 parts per million of gluten. However, Dr. Nazareth notes that some people with celiac disease react to less gluten than this. Also, people taking probiotics may tend to take multiple capsules of the product, which could exacerbate the effect of any trace gluten present.

Study Looked at Most Popular Probiotic Brands

The study authors decided to test probiotics for trace gluten cross-contamination because out of all the various types of supplements, probiotics were the most popular products used by people with celiac disease, says Dr. Nazareth, who's a gastroenterology fellow at New York Presbyterian-Columbia.

To determine which brands to test, she says she simply visited and looked at the list of top-selling probiotics. The study also included two drug store brands.

Before testing the samples, the researchers first "digested" them with three different types of digestive enzymes. They then subjected them to a very sensitive screening process using liquid chromatography-mass spectrometry, which both can detect gluten down to one part per million and can differentiate between wheat, barley and rye proteins.

Of the 22 probiotics, 12 contained gluten, including eight that were labeled "gluten-free" and four that were not. Two of these eight "gluten-free"-labeled (yet gluten-containing) probiotics contained more than the legal "gluten-free" standard of less than 20 parts per million, Dr. Nazareth says.

Meanwhile, four out of the seven probiotics not labeled "gluten-free" tested positive for gluten, including two that contained more than 20 parts per million, she says.

Both wheat and barley were detected in four of the 22 probiotics, even though two of these were labeled "gluten-free."

Which Brands Had the Gluten?

Unfortunately, Dr. Nazareth declines to disclose the brand names of the gluten-containing probiotics, saying gluten content might vary from batch to batch (the researchers only tested one pill from one bottle of each brand).

She says price didn't make that much difference, as at least one expensive brand tested positive: "A probiotic labeled 'gluten-free' that cost $55 had between one and 20 parts per million of barley in it."

Both of the "gluten-free"-labeled probiotics that exceeded the legal "gluten-free" limit included both wheat and barley (one had between 20 and 100 parts per million of wheat along with trace amounts of barley in it, while the other had trace amounts of wheat and between 20 and 100 parts per million of barley in it). Dr. Nazareth says these two products cost around $20 and $28, respectively.

So What Can We Do To Get Safe Probiotics?

First, Dr. Nazareth stresses that the trace gluten in these may not bother everyone with celiac disease, since sensitivity can vary tremendously from person to person. However, the amounts in the probiotics tested were concerning enough that researchers were disappointed in what the study revealed, she says.

Since over-the-counter supplements are generally unregulated and aren't required to be tested, anyone taking probiotics who avoids gluten should be aware of the possibility of cross-contamination and monitor their symptoms, Dr. Nazareth says, adding, "be mindful of what you're taking."

In addition, she urges discussing supplement use — including use of probiotics — with your doctor.

Beyond that, there's little you can do to protect yourself except push federal rulemakers to enact standards for over-the-counter supplements, Dr. Nazareth says: "Ultimately, our hope is that the public would direct their concerns to the appropriate regulatory authority."

Could other types of supplements — say, vitamins and minerals, also commonly taken by people with celiac disease and non-celiac gluten sensitivity — be as cross-contaminated as probiotics? Dr. Nazareth and her colleagues didn't test any other types of supplements, but she says it's certainly a possibility. She says her group hopes to expand its research into trace gluten content in over-the-counter supplements.


Nazareth S. et al. "Widespread Contamination of Probiotics with Gluten, Detected by Liquid Chromatography-Mass Spectrometry." Presented May 16 at Digestive Disease Week 2015.

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