• Irritable bowel syndrome (IBS) affects an estimated 3–5% of the global population.
• Food and stress can trigger IBS symptoms.
• A new study has shown no effect on IBS symptoms from consuming gluten.
• The authors also reveal that dietary restriction of fermentable carbohydrates has a small, modest benefit on symptoms.
• The researchers recommend an individualized, holistic approach to treating IBS.

IBS is a chronic bowel disorder that health experts characterize by abdominal pain and changes in bowel movements. People with the condition may experience one of four subtypes:

• IBS with constipation (IBS-C)
• IBS with diarrhea (IBS-D)
• IBS with a mix of constipation and diarrhea (IBS-M)
• Unsubtyped IBS (IBS-U)

Doctors classify IBS as a functional gastrointestinal disorder. Scientists believe that this group of conditions is due to disturbances in gut-brain interactions.

However, there is no specific, underlying pathology, making them challenging to diagnose and treat.

According to research, people living with IBS can experience a lower quality of life than individuals with conditions such as kidney disorders and diabetes.

IBS triggers

Regarding triggers for IBS, Dr. Ashkan Farhadi, a doctor and researcher, told Medical News Today that IBS can be instigated by:

• infections, such as gastroenteritis
• post-surgery factors, including after abdominal surgery
• post-traumatic stress following emotional life events
• unknown causes, including possibly genetic factors

Fermentable carbohydrates and gluten

Researchers in Sweden recently published a large study evaluating specific food types and their effect on IBS. The results appear in the American Journal of Clinical Nutrition.

They compared and contrasted two dietary restrictions frequently recommended to people living with IBS — removing gluten or fermentable carbohydrates from their diet.

Fermentable carbohydrates are oligo-, di-, monosaccharides, and polyols (FODMAPS). They are in many foods, including some vegetables and most legumes.

Many people believe FODMAPS cause IBS symptoms because they are rapidly fermented by gut bacteria and, therefore, may cause abdominal distention, bloating, and pain.

Gluten is a protein present in wheat, rye, barley, and triticale, a cross between wheat and rye. Manufacturers also add gluten to some processed foods to improve their texture.

First author, Elise Nordin, a Ph.D. candidate at the division of Food and Nutrition Science at Chalmers University of Technology in Sweden, explained to MNT:

“FODMAPS are poorly absorbed and fermentable carbohydrates. A too high intake will cause symptoms also in healthy people. Previously, research has shown that people with IBS may be more sensitive [to FODMAPS] compared with healthy people. Thereby the belief has been that by excluding FODMAPS, they will gain symptom relief.”

Preconceived notions

Elise Nordin, principal author Prof. Per Hellström, and Prof. Rikard Landberg challenged these long-held notions that restricting FODMAPS and gluten benefits individuals.

They achieved this by performing a large, randomized, double-blind study comparing people with IBS on three diet types. This study is the first of its kind to make these direct dietary comparisons.

Nordin, Rikard, and Hellström studied 103 people who fulfilled the diagnostic criteria for moderate-to-severe IBS. The team randomly assigned them food “challenges” that were either rich in FODMAPS, rich in gluten, or a placebo with nothing added to it.

Then, following a week of eating a diet low in FODMAPS and gluten, the researchers put the participants onto another food challenge. After another week of low FODMAPS and gluten, the participants tried the third diet.

The scientists then used a vetted IBS-severity scoring system (IBS-SSS) to assess how IBS symptoms changed.

Confirmed and denied

The results diverged. People with IBS who ate the FODMAPS diet experienced more IBS symptoms, scoring higher on the IBS-SSS.

However, those individuals eating a gluten-heavy diet did not have significantly higher scores.

Interestingly, all participants’ symptoms improved when they ate the combined low FODMAPS and low gluten washout diet. The scientists conclude this improvement might be due to:

• drastically reduced FODMAP and gluten intake during the washout diet period compared with participants’ usual choices
• people being more careful when they knew they were involved in a study (study bias) and more regular meal patterns
• enhanced psychological well-being due to increased medical attention

On the subject of gluten

As a gastroenterologist, Dr. Farhadi stressed to MNT the importance of improving our understanding of gluten in the diet. He commented:

“There are many people with celiac disease [who] are not aware of their disease. They can present with IBS-like symptoms for decades.”

“Finding those individuals is very important and should be done. There is another important category in IBS, which is nonceliac gluten enteropathy. […] These are people who do not have celiac disease, and [yet] they cannot tolerate gluten. […] That is why it is important to leave the options for the diet open to the patient.”

Good science, new knowledge

For MNT, first author Elise Nordin explained the study’s conclusions:

“Our study shows that gluten has no effect on IBS symptoms. We performed a large, double-blinded intervention trial, and our results are in accordance with several other trials. There is accumulating evidence suggesting that gluten, per se, may not cause adverse effects on a group level among subjects with IBS.”

“From the available evidence, it should be possible to dismiss a general adverse effect by gluten on IBS symptoms. However, we shall acknowledge that reactions are very individual, and we also observed adverse effects among some individuals in our study.”

What about FODMAPS?

Nordin further elaborated, “Concerning FODMAPS, the adverse effect was smaller (on a group level) than anticipated.” She also explained that, because IBS symptoms and triggers vary between individuals, people with IBS should enter a “close dialogue with their [doctor] to test specific FODMAP sources.”

In this way, each individual can slowly eliminate or diminish “the specific problematic foods in their diet and keep other sources, if possible, to avoid cutting down dietary fiber-rich foods that may not cause problems.”

In summary, Elise Nordin commented:

“From a treatment perspective of IBS, there is a general agreement that a holistic perspective is needed, including medical treatment, change in lifestyle factors, and psychological treatments. Our results are in line with these guidelines and indicate that IBS is more complex than a simple connection to diet.”

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