Fructan, not gluten, may be the real culprit of stomach symptoms, study finds

In a study of people with gluten sensitivity not due to celiac disease, researchers found that fructans caused more gastrointestinal symptoms than gluten itself.

Fructans are non-digestible carbohydrates that belong to the class of FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols).

“The finding weakens the use of the term ‘non-celiac gluten sensitivity’ and raises doubts about the need for a gluten-free diet in individuals that self-report gluten sensitivity,” wrote researchers led by Gry I. Skodje, MSc, RD, Department of Clinical Nutrition, Division of Cancer Medicine, Oslo University Hospital, Oslo, Norway, in a recent article in Gastroenterology.

The prevalence of celiac disease in the United States is less than 1%, yet the number of Americans who follow a gluten-free diet is much higher, and increasing.

The fructan effect

Although gluten has been shown to induce symptoms in some studies, the same result hasn’t been found in placebo-controlled crossover studies.

So, for this investigation, researchers conducted a randomized, double-blind, placebo-controlled crossover study of 59 adults, aged 18 to 80 years, with self-reported nonceliac gluten sensitivity. All participants were required to eat a daily muesli bar. Participants were randomly assigned to groups in which the muesli bar contained either gluten (5.7 g), fructans (2.1 g), or placebo.

The amounts of gluten and fructans in each bar were equivalent to the amounts of gluten and fructans found in 4 slices of wheat bread.

Each group ate the same type of bar for 7 days, which was followed by a minimum 7-day washout period to allow for any symptoms to resolve. Then participants crossed over into a different group until they completed 7-day courses of all three types of bars.

At the end of the study, researchers found that fructans induced more symptoms than gluten or placebo, as measured by the Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome (GSRS-IBS).

“The overall GSRS-IBS score for participants consuming fructans was significantly higher than for participants consuming gluten (P = .049), as was the GSRS bloating score (P = .003),” researchers wrote.

“Although the differences in the symptoms induced across the challenges were small, the fructan effect was distinct and consistent for many symptoms,” they noted.

The more likely culprit

Upon further analysis, researchers found that 24 participants had the highest overall GSRS-IBS score after eating the bar containing fructans, 22 participants had the highest score after having the placebo bar, but only 13 had the highest score after consuming gluten.

Moreover, 27 participants had the lowest score after eating the gluten bar.

“The current findings contrast [with] previous studies and weaken the role of gluten as a symptom trigger in individuals intolerant of wheat, rye, or barley. Rather, the results indicate that fructans are more likely the culprits,” the authors concluded.

Some people may indeed have fewer symptoms on a self-imposed gluten-free diet, the researchers acknowledged. However, these improvements may not be caused by eliminating gluten but rather from the coinciding reduction of wheat fructans.

This study was funded by the Extra Foundation Health and Rehabilitation, the Norwegian Celiac Association, the Throne Holst Foundation for Nutrition Research, and the Wedel Jarlsberg Foundation.