By Amy Ratner

Medical and Science News Analyst

Both gluten sensitivity and irritable bowel syndrome result in intestinal and other symptoms similar to those found in celiac disease, but neither has a test that can confirm a diagnosis.

A recent review of research into gluten sensitivity and irritable bowel syndrome by 23 international experts published in the journal, Nutrients, was designed to update understanding of the complex relationship between the two. Study authors included Alessio Fasano, M.D. director of the Center for Celiac Research at Massachusetts General Hospital for Children and Armin Alaedini, Ph.D, scientific director at the Celiac Disease Center, Columbia University Medical Center.

The study review concluded that a gluten-free diet can benefit both gluten sensitive patients who report gluten-related symptoms and IBS patients who are also gluten or wheat sensitive.

Estimates vary widely, but studies have put the number of people with gluten sensitivity internationally as high as 10 percent of the general population, while the prevalence of IBS worldwide is estimated to be 10 to 20 percent.

The review included research published since a previous investigation in 2014, as well as key historical papers and emerging studies. Experts specifically looked at prevalence studies of gluten sensitivity, non-IgE wheat allergy, potentially harmful wheat components, mechanisms for IBS triggered by wheat and the overlap between IBS symptoms and gluten sensitivity.

“Public and commercial interest in the gluten-free diet has galvanized the scientific community into undertaking research beyond the previously recognized gluten-related disorders such as celiac disease or dermatitis herpetiformis,” researchers wrote, noting the number of studies has nearly quadrupled since 2000. Recent studies, they said, “support the hypothesis that gluten and other wheat components” might trigger IBS symptoms.

Even with the increase in research interest, data on the overlap between symptoms of gluten sensitivity and IBS is limited, the study says. This is partially because patients who have gone on the gluten-free diet without a diagnosis are reluctant to eat gluten for fear of becoming sick again. This makes it difficult to follow the double-blind placebo controlled approach recommended for diagnosis.

A hypothesis that gluten sensitivity could be a non-IgE-mediated wheat allergy is based on clinical characteristics, tests results and new endoscopic findings, but the study review cautions that more work is needed to clarify any relationship.

Still, the study review notes a that substantial subset of patients with IBS are likely to be wheat sensitive. A recent clinical trial in patients with IBS with diarrhea confirmed the close relationship between wheat-containing food and a subgroup of IBS cases.

Meanwhile, several components of wheat are cited as being potentially harmful for gluten sensitive and IBS patients, including fermentable, oligo-, di- and mono-saccharides and polyols, better known as FODMAPs. These include fructans, lactose, fructose and sugar alcohols, such as sorbitol, mannitol, xylitol and maltitol. FODMAPs are resistant to digestion and absorption in the small intestine, with complete or partial fermentation in the large intestine. Wheat, barley and rye — the gluten-containing grains — are all high in FODMAPs.

Read more: What are FODMAPs and what is the connection to gluten sensitivity and celiac disease?

However, FODMAPs do not trigger neurological and other non-intestinal symptoms of gluten sensitivity, which the study review says are most likely caused by the proteins in wheat, including gluten.

“Regardless of the identification of the offending components, the scientific community agrees that the withdrawal of wheat … can significantly improve symptoms in a subset of IBS patients, who can sometimes be diagnosed as (gluten sensitive),” researchers write.

They note that current evidence shows that a gluten-free, and thus wheat-free, diet could be beneficial for a subgroup of IBS patients found to have “gluten sensitive IBS.”

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