Sales of gluten-free products has sky rocked globally the last couple of years. In Norway, the sales of gluten-free products has increased with 35 % from last year. Gluten often gets blamed for a host of issues including GI problems, but maybe it is not the gluten?

What is gluten?

Gluten is a protein consisting of gliadin and glutenin. It is widely used in baking because it acts as a good binder and ads structure to baked goods. Gluten is found in most common grains like wheat,spelt, barley and rye. Oats are naturally gluten free but, can become contaminated when processed in facilities that also process grains with gluten. Corn, rice, millet and buckwheat is gluten-free. Some people need to avoid gluten completely and that is people who suffer from celiac disease.

Celiac disease

Celiac disease is an autoimmune disease caused by a hypersensitivity to gluten. This means that the consumption of gluten for those with this condition will cause the immune system to attack its own tissue. Untreated, the mucosa in the small intestines will get inflamed and cause damage to the villi. This can lead to abdominal pain, diarrhoea, blood in the stool, weight loss and malabsorption. It is also very common to be lactose intolerant when the celiac disease is untreated. For those with celiac disease, the only treatment is to follow a gluten-free diet. This can be a challenge because gluten is often hidden in a variety of foods and under different names, so it is very important to carefully read nutrition declarations. The question is if people without celiac disease also can react to gluten and the term “non-celiac gluten intolerance” has in recent years got a lot of attention.

Non-celiac gluten intolerance

Non-celiac gluten intolerance is a syndrome where one experiences many of the same gastrointestinal symptoms as people with celiac disease, but there is no damage to the small intestines mucosa. In addition, many also experience symptoms unrelated to the stomach and intestines such as depression, muscle pain, joint pain, headaches and chronic fatigue. The question researchers have asked is whether it is gluten that causes these problems for these people or whether it may be something else?

At the University of Monash in Australia, Biesiekierski and colleges wanted to find an answer to this. In 2011, they conducted a study on participants who had irritable bowel syndrome (IBS) and followed a gluten-free diet1. The participants had their IBS in remission and the researchers wanted to examine whether symptoms returned if gluten was reintroduced into their diet. The study was a double-blind, placebo-controlled study with 34 participants and the majority where females. All participants were given a gluten-free diet for 6 weeks, but 19 of the participants where given two slices of bread and a muffin daily that contained gluten, while the rest where given bread and muffin that where gluten free. The results showed that approximately 68% of participants in the gluten group experienced a worsening of their condition with recurrence of symptoms, while 40% in the placebo group  experienced the same. This showed a statistically higher incidence of worsening of symptoms in the group receiving gluten compared with placebo. The researchers therefore concluded that non-celiac gluten intolerance could be a real phenomenon.

As mentioned, the study was conducted on patients with IBS and in recent years, there has been a diet called FODMAP that has shown to be highly effective to control the symptoms of IBS.


FODMAP (fermentable oligo-, di-, monosaccharides and polyols) are short-chain carbohydrates which are digested poorly in the small intestines. The diet was developed by Dr.Sue Sheperd in Australia and is currently recognized and used to a great extent in the treatment of IBS. Several studies have reported improvements for people with IBS by following this diet and a review from 2013 reported that over 85 % of people with IBS that follow a low FODMAP diet see good improvements2.

Biesiekierski and his colleagues felt that their study had some weaknesses and therefore wanted to conduct a new study in which they controlled for several variables3. In this study, 37 participants followed a low FODMAP and gluten-free diet for 2 weeks. After these two weeks, participants where given various amounts of gluten for a week. One group received 16 g of gluten, the other group got 2 g of gluten and 14 g of milk protein (whey protein isolate) and the last group received 16 g of milk protein only (whey protein isolate). After this week, the groups had a 2-week washout period before they switched to the next group. In other words, all the groups where exposed to the various amounts of gluten in this study. Many of the participants experienced improvement in symptoms during the first 2 weeks of the low FODMAP and gluten-free diet, but in this study the researchers were unable to see a clear correlation with worsening of symptoms with ingestion of gluten. It was therefore concluded that there was no clear findings on gluten intolerance when participants were placed on a low FODMAP diet.

A recent study by Volta and colleges, evaluated 12,255 patients who suspected that they had non-celiac gluten intolerance4. They found that approximately 3% of the participants had celiac disease and that about half of the participants had clear symptoms indicating that they had IBS.


Biesiekierski and colleagues second study argues against the findings they found in the first study.  The second study was much better controlled when participants got to try different diets and it was also controlled for FODMAP. This may indicate that there is possibly high FODMAP foods that causes a problem for many people and that it is not necessarily the gluten that is the problem.

By eliminating gluten from the diet, you will also automatically eliminate a lot of high FODMAP foods. That is not to say that non-celiac gluten intolerance might not be a real condition, but it may indicate that it possibly for many, other things than gluten that is causing their GI distress.

Finally, it is important to mention that if one feels that their symptoms gets improved by following a gluten-free diet, then that is the most important thing. However, it may still be wise to find out what causes these problems before setting out on a somewhat restrictive diet that gluten-free diet can be experienced as.


1.Biesiekierski JR et al. Gluten Causes gastrointestinal symptoms in subjects without celiac disease: a double-blind randomized placebo-controlled trial. Am. J. Gastroenterol. 2011; 106 (3): 508-14

2. Barrett JS. Extending our knowledge of fermentable, short-chain carbohydrates for managing gastrointestinal symptoms. Nutr. Clin. Pract. 2013; 28: 300-6

3.Biesiekierski JR et al. No effects of gluten in Patients with self-Reported non-Celiac gluten sensitivity after dietary reduction of fermentable, poorly absorbed, short-chain carbohydrates. Gastroenterology 2013; 145 (2): 320-8.e1-3

4.Volta U et al. An Italian prospective multicentre survey on patients suspected of having non-celiac gluten sensitivity. BMC Med. 2014; 12: 85