People with celiac disease might unknowingly be consuming gluten in their probiotic, report medical chemists who found trace amounts of gluten in about half of products labeled gluten-free.

“Gluten-free labelling does not accurately reflect the gluten content of probiotics,” said Samantha Nazareth, MD, from Columbia University in New York City.

The existing treatment for celiac disease, which affects approximately 1% of the population, is the lifelong exclusion of gluten. However, because inadvertent gluten exposure is common, this can be a challenge, Dr Nazareth explained.

Although gluten-free diets have gained in popularity, even among people without celiac disease, her main concern is for patients with sensitivities because of damage in the small intestine, she told Medscape Medical News. “Gluten definitely causes harm to them.”

People with celiac disease “should be aware of the potential for contamination with gluten, regardless of what the label says,” Dr Nazareth said. “Patients must take caution. They don’t know what they are getting.”

The US Food and Drug Administration (FDA) regulates the gluten-free label. It can only be used on products that contain less than 20 ppm of gluten; do not contain wheat, rye, or barley; and do not have an ingredient derived from these grains.

The FDA does not regulate herbal products, although 24% of patients with celiac disease take dietary supplements, most commonly probiotics, according to a previous study Dr Nazareth was involved in (J Clin Gastroenterol. Published online September 8, 2014).

Many Gluten-Free Claims Are False

Because symptoms related to celiac disease are reported more often by patients who take supplements than by those who do not, “our current study aimed to measure for the presence of gluten in popular probiotics,” Dr Nazareth explained.
Her team evaluated 22 of the most popular brands of probiotics on the national market. For each sample, they digested the probiotic 30 mg with pepsin, trypsin, and chymotrypsin. The researchers then conducted liquid chromatography–mass spectrometry analysis and quantitated marker peptides that represented wheat, barley, and rye.

They found that more than half of the probiotics labeled gluten-free contained the protein composite, and some of these contained more than 20 ppm, which exceeds the FDA threshold for the gluten-free labeling of food, Dr Nazareth pointed out.

Table. Analysis of Products Labeled Gluten-Free (n = 15)

Gluten Content Percent
Contained the protein composite 53
Contained more than 20 ppm 13.

Seven of the 22 probiotics, or 31%, were not labeled gluten-free. Of these, four tested positive for gluten, and two contained more than 20 ppm.

Twelve of the 22 probiotics, or 55%, actually contained some measure of gluten. Of these, eight, or 67%, were labeled gluten-free.

More than one gluten component — wheat, rye, or barley — was detectable in four of the 22 probiotics, and two of these products were labeled gluten-free.
It is not known how much gluten is safe for patients with celiac disease. Trace amounts are probably not enough to induce villous atrophy, Dr Nazareth acknowledged, but it is possible that any amount could aggravate symptoms. The biggest concern is that two of the 22 products exceeded the FDA threshold.

“The amount of gluten in probiotics may be significant, especially if one considers the cumulative number of capsules consumed,” she pointed out.

Dr Nazareth advised physicians to ask patients about probiotic use and to consider the possibility of contamination with gluten.

It’s still a bit of the Wild West out there.
Are people with celiac disease deriving enough benefit to accept the risk of inadvertent gluten contamination? The benefit of probiotics has not been firmly established in terms of improving markers of disease, although patients have reported improvements in some symptoms, Dr Nazareth explained.

The potential contamination of probiotics with gluten is “a huge issue,” said Jenifer Lightdale, MD, from the University of Massachusetts Medical School in Worcester.

She praised the researchers for “starting to get at the fact that people with celiac disease need to be safe and to really question everything they are taking.”

“There’s been a movement toward feeling comfortable about probiotics, which is great, but maybe not for patients with celiac disease,” she told Medscape Medical News.

Dr Lightdale added that inadvertent exposure in children with celiac disease might affect growth, without warning. “Some kids don’t realize they don’t feel well, and it may take a while to realize they are being exposed to gluten,” she explained.

“We clearly need to regulate gluten-free products, including supplements. In fact, this study speaks to the need to regulate probiotics in general. It’s still a bit of the Wild West out there,” she said.

“People are interested in gluten-free diets and in probiotics. These two movements are merging, and we need to make sure that probiotics are clear on whether they contain gluten,” Dr Lightdale said.