FODMAP vs Gluten: The Difference and What It Means for IBS
Updated October 2026
Wheat, rye and barley contain two substances that are often confused: the protein gluten, and fructans, which are FODMAPs. In irritable bowel syndrome (IBS), it is usually the fructans that cause symptoms. In coeliac disease, it is the gluten. This guide explains how FODMAPs and gluten differ, what studies on gluten sensitivity show and what to do if bread and pasta disagree with you.
Key points
- FODMAPs are carbohydrates, while gluten is a protein. Wheat, rye and barley contain both. The fructans in these grains are FODMAPs.
- In IBS, symptoms are usually triggered by the fructans, not the gluten. Several blinded studies show this.
- In coeliac disease, even small amounts of gluten damage the small intestine. A strict gluten-free diet for life is needed. The FODMAP diet does not replace it.
- The FODMAP diet is not gluten-free, and gluten-free products are not automatically low FODMAP. It depends on the ingredients and the amount.
- Coeliac disease is diagnosed with a blood test and usually a biopsy of the small intestine. The test is only reliable while you are eating gluten regularly.
FODMAP vs gluten: what is the difference?
FODMAPs are short-chain carbohydrates that the small intestine absorbs poorly. In the large intestine, they are fermented by bacteria. They include fructans, which are chains of fructose. Fructans are found in wheat, rye and barley, but also in onions and garlic. We explain the six FODMAP groups in our article What are FODMAPs?
Gluten, on the other hand, is a protein, or more precisely a mixture of storage proteins in the grain. It makes dough elastic and bread light and airy. Gluten is found in all types of wheat, including spelt, emmer, einkorn and Kamut, as well as in rye, barley and triticale. Oats are a special case: most people with coeliac disease tolerate the protein in oats, but ordinary oats are often contaminated with wheat, rye or barley.
| FODMAPs | Gluten | |
|---|---|---|
| What it is | Carbohydrates and sugar alcohols | A protein found in grains |
| Found in | Wheat, rye, barley, onions, garlic, beans, lentils, milk, some fruits | Wheat and spelt, rye and barley |
| Who reacts | Many people with IBS | People with coeliac disease, and people with a wheat allergy, who also react to other proteins |
| In the body | In the gut, they draw in water and are fermented. A sensitive gut reacts with bloating, pain or diarrhoea. | In coeliac disease, the immune system attacks the small intestine. |
| Damage to the gut | None. The symptoms are unpleasant, but not dangerous | Yes, in untreated coeliac disease, with consequences such as iron deficiency or osteoporosis |
| Small amounts | Usually well tolerated | Harmful in coeliac disease |
| Diet | Low FODMAP for 2 to 6 weeks, then testing and relaxing the diet | Strictly gluten-free for life in coeliac disease |
| Test | No lab test. Cutting foods out and then testing them shows what you tolerate | Blood test for antibodies, usually followed by a biopsy of the small intestine |
The FODMAP diet is intended for people with IBS. Different rules apply to coeliac disease and wheat allergy.
Good to know: Spelt is a type of wheat and contains gluten. It is therefore not suitable for people with coeliac disease or a wheat allergy, not even as sourdough bread. In IBS, on the other hand, spelt sourdough bread is often well tolerated because it contains few fructans.
Coeliac disease, wheat allergy and wheat sensitivity
If bread or pasta gives you symptoms, there are three possible causes besides IBS. They have very different consequences for your diet, so it is worth telling them apart.
In people with a genetic predisposition, gluten triggers an immune reaction that damages the lining of the small intestine. Nutrients are then absorbed less well. Possible symptoms include diarrhoea, bloating, abdominal pain, tiredness, iron deficiency or weight loss, while some people notice hardly anything. In Switzerland, around 1 per cent of the population is affected, many of them undiagnosed. Treatment: a strict gluten-free diet for life.
The immune system reacts allergically to proteins in wheat, including gluten. Symptoms usually appear within minutes to an hour, often as itching, hives or swelling, and rarely as anaphylactic shock. It mainly affects children, who often grow out of it. Treatment: avoiding wheat and related grains such as spelt.
Also known as non-coeliac gluten sensitivity, this term describes symptoms after eating wheat when coeliac disease and allergy have been ruled out. There is no test for it, and there is no damage to the gut and no typical antibodies. What triggers the symptoms is disputed. For many people, it does not seem to be the gluten, as the studies below show.
Coeliac disease can feel just like IBS. According to the British Society of Gastroenterology (BSG), a positive coeliac blood test is almost three times as common in people with IBS symptoms as in people without them. That is why the guidelines recommend testing for coeliac disease if you have IBS symptoms.
Fructans, not gluten: what the studies show
Many people feel better without wheat and conclude that they cannot tolerate gluten. But if you cut out wheat, you also eat fewer fructans. Researchers have used blinded studies to find out which of the two triggers the symptoms. The participants did not know whether they were getting gluten, fructans or a placebo.
In this study, 37 people with IBS who believed they were sensitive to gluten first followed a low FODMAP diet for two weeks. During this time, their symptoms eased considerably. They were then given a lot of gluten, a little gluten or a placebo, each for one week. Symptoms increased to a similar degree with gluten and with the placebo. Only 3 of the 37 people showed a clear reaction to gluten.
Here, 59 people on a gluten-free diet because of suspected gluten sensitivity ate muesli bars for a week at a time. The bars contained 5.7 g of gluten, 2.1 g of fructans or neither. Those with fructans caused more symptoms and bloating than those with gluten. Gluten had no more effect than the placebo.
A total of 103 people with IBS followed a low FODMAP, gluten-free diet. On top of this, they were given a lot of FODMAPs, a lot of gluten or a placebo, each for one week. The FODMAPs moderately increased typical symptoms, while gluten had no effect.
This study involved 84 people with suspected gluten sensitivity, who ate bread with or without gluten. Some of them were told that the bread contained gluten. Those who ate gluten and also expected it had the most symptoms. The researchers see this as a nocebo effect, but an additional effect of gluten could not be ruled out.
A review published in The Lancet in 2025 found that around 10 per cent of adults worldwide say they cannot tolerate gluten or wheat. In controlled tests, however, only 16 to 30 per cent of them react specifically to gluten. In many cases, fermentable carbohydrates such as fructans and expectation effects contribute significantly to symptoms. Other components of wheat, such as amylase-trypsin inhibitors (ATIs), are also being discussed. No single clear trigger has been proven so far.
What this means for you: If you have IBS and bread gives you trouble, the fructans are often the reason. The BSG does not recommend a gluten-free diet for IBS. The FODMAP diet is more targeted: during reintroduction, you find out how much wheat you can tolerate.
Why the FODMAP diet is not gluten-free
The FODMAP diet is about carbohydrates. In the first phase, you limit wheat, rye and barley because of their fructans, not because of the gluten. You do not need to go gluten-free, and small amounts of wheat are allowed. According to Monash University, these foods containing gluten fit into the FODMAP diet in normal amounts:
Spelt contains fewer fructans than modern wheat. In traditional sourdough, which is left to rise for a long time, yeasts and lactic acid bacteria break down even more of the fructans.
Oats are low FODMAP in normal portions. Exactly how much you can eat depends on the form: rolled oats, quick oats or whole oat grains. You will find the amounts in the Monash FODMAP app.
Soy sauce is often brewed with wheat and then contains gluten. It is still low FODMAP.
These ingredients in ready-made products contain gluten but hardly any fructans. Small amounts of biscuits, crackers or cake made with wheat are also often well tolerated.
According to Monash, traditional wheat sourdough bread is also low FODMAP in a portion of 2 slices. Rye sourdough bread, on the other hand, remains high FODMAP. Not every loaf labelled sourdough is left to rise long enough, and some also contain added yeast and have only a short proving time. Ask at the bakery which flour is used and whether the dough is left to rest for a long time, for example overnight.
What is allowed on the FODMAP diet can be harmful in coeliac disease. Spelt sourdough bread, barley malt, soy sauce made with wheat and oats not labelled gluten-free are then off-limits. That is why the FODMAP diet is no substitute for a gluten-free diet.
Why gluten-free is not automatically low FODMAP
Many gluten-free products are made from rice, corn or potato flour. These are low FODMAP, which is why gluten-free bread and pasta often fit well into the FODMAP diet. However, manufacturers sometimes add high FODMAP ingredients for flavour or extra fibre. It is worth checking the ingredients list.
Watch out for
- Inulin, chicory root fibre or fructo-oligosaccharides (FOS): fructans, even small amounts count
- Honey, agave syrup, fructose syrup or fruit juice concentrate: too much fructose
- Soya, lupin or chickpea flour: GOS and fructans, for example in gluten-free pasta
- Onion or garlic powder: in bread, sauces and stock
Naturally gluten-free and low FODMAP
- Rice, corn and polenta
- Potatoes
- Quinoa and millet
- Flour made from rice, corn, buckwheat or quinoa
- Pasta made from rice, corn or quinoa
In coeliac disease, processing matters too. Even naturally gluten-free flours and flakes can be contaminated with gluten during harvesting and processing. Products labelled ‘gluten-free’ are suitable. In Switzerland and the EU, they may contain no more than 20 mg of gluten per kilogram. Many also carry the gluten-free symbol, a crossed-out ear of wheat.
Tip: Our FODMAP list shows which grains, breads and flours are low FODMAP. For exact portion sizes and certified products, see the Monash FODMAP app.
What to do: IBS or suspected coeliac disease
Only a test can show whether coeliac disease is behind your symptoms. If you avoid gluten before the test, you risk a false negative result. Blood in your stool, unintentional weight loss, iron deficiency or diarrhoea at night are not typical of IBS and can have another cause.
If you suspect coeliac disease
Eating gluten until the test. According to the German guideline on coeliac disease, at least one or two of your daily meals should include bread, baked goods or pasta until you are tested. A FODMAP diet or a gluten-free diet before the test can skew the result.
Blood test and biopsy. The blood is tested for antibodies against tissue transglutaminase (tTG-IgA) and for total IgA. If the result is abnormal, adults usually have a gastroscopy with biopsies taken from the small intestine.
Gluten-free after diagnosis. The treatment is a strict gluten-free diet for life, because even small amounts of gluten damage the gut.
Get support. The IG Zöliakie der Deutschen Schweiz (the coeliac society for German-speaking Switzerland) and, in Germany, the Deutsche Zöliakie-Gesellschaft (German Coeliac Society) provide information on living with coeliac disease and on the gluten-free diet.
Already gluten-free but never tested? Then you will need a gluten challenge before the test. The BSG recommends 3 to 6 g of gluten a day for at least 6 weeks, while the German guideline recommends about 10 g a day, preferably for 3 months. A 40 g slice of wheat bread contains around 2.5 g of gluten. If you do not tolerate wheat well because of the fructans, the BSG suggests spelt sourdough bread as a source of gluten with fewer FODMAPs.
If you have IBS but not coeliac disease
Blood test for coeliac disease. According to the guidelines, it is part of the standard assessment for IBS. You can read how the diagnosis works in our article Irritable bowel syndrome: symptoms, causes, diagnosis and treatment.
Reduce wheat rather than banning it. In the first phase of the FODMAP diet, you replace large portions of wheat, rye and barley, for example with spelt sourdough bread, rolled oats, rice, potatoes or gluten-free products without high FODMAP ingredients. Small amounts of wheat are still allowed.
Test fructans specifically. During reintroduction, you find out whether you tolerate wheat and how much, for example with wheat pasta. Our reintroduction test plan shows the process and starting amounts.
Do not stay gluten-free unnecessarily. Grains, especially wholegrains, provide fibre, vitamins and minerals. Cutting out gluten for good without a medical reason restricts your diet more than it needs to.
An itchy mouth, hives, swelling or shortness of breath shortly after eating point more towards an allergy. Shortness of breath or circulation problems after eating are a medical emergency (emergency number 144 in Switzerland, 112 in the EU).
Coeliac disease and IBS at the same time
Some people with coeliac disease still have abdominal symptoms despite a strict gluten-free diet. If hidden gluten is not the cause, a low FODMAP diet on top can help. In a Norwegian study of 70 people, symptoms eased within a week, and the effect lasted for the four weeks of the study.
Enzymes for wheat
According to the manufacturer, the enzyme product FODZYME breaks down fructans from wheat, barley and rye while they are still in the food. It does not break down gluten, and it is explicitly not intended to make food containing gluten suitable for people with coeliac disease. So far, the evidence comes mainly from laboratory and observational studies. It is best not to use it during elimination and reintroduction, so that your tests remain meaningful. Read more in our FODZYME FAQ.
Frequently asked questions about FODMAPs and gluten
Is gluten a FODMAP?
No. Gluten is a protein, while FODMAPs are carbohydrates. Because wheat, rye and barley contain both, the terms are often confused. In IBS, it is usually the fructans in these grains that cause symptoms.
Is the FODMAP diet gluten-free?
No. Wheat, rye and barley are only limited because of their fructans. Small amounts of wheat, spelt sourdough bread, rolled oats or soy sauce are allowed. That is why the FODMAP diet is not enough if you have coeliac disease.
Are gluten-free products low FODMAP?
Often, but not always. Many are made from low FODMAP rice, corn or potato flour. Some, however, contain inulin, honey, fruit juice concentrate or flour made from pulses. So check the ingredients list, and use our FODMAP list as a guide.
Is spelt easier to tolerate than wheat if you have IBS?
Often, yes, especially as traditional sourdough bread. Spelt contains fewer fructans than modern wheat, and the long resting time of the dough breaks down even more. Spelt flour and spelt products made without a long rest contain far more fructans, though, and the Monash app shows which amounts are fine. If you have coeliac disease or a wheat allergy, spelt is unsuitable in any form.
Does a gluten-free diet help with IBS?
The British Society of Gastroenterology (BSG) does not recommend it for IBS. If you feel better without wheat, you are usually reacting to the fructans. The FODMAP diet with reintroduction is more targeted and less restrictive. If you go gluten-free before a coeliac test, you risk a false negative result.
Can I follow a low FODMAP diet if I have coeliac disease?
Yes, as long as your diet stays strictly gluten-free. This can make sense if abdominal symptoms persist despite a gluten-free diet and other causes, such as hidden gluten, have been ruled out.
Are gluten-free products suitable if I have a wheat allergy?
Not always. Gluten-free products can contain other wheat proteins, for example in the form of gluten-free wheat starch, and up to 20 mg of gluten per kilogram. If you have a wheat allergy, the ingredients list is what counts. In Switzerland and the EU, wheat must be highlighted in it.
Sources: Monash University, Gluten and IBS (2021) · Monash University, FODMAP FAQs · Monash University, Label reading and FODMAPs (2021) · Monash University, Sourdough processing and FODMAPs (2017) · Biesiekierski et al., No effects of gluten in patients with self-reported non-celiac gluten sensitivity (Gastroenterology 2013) · Skodje et al., Fructan, rather than gluten, induces symptoms in patients with self-reported non-celiac gluten sensitivity (Gastroenterology 2018) · Nordin et al., FODMAPs, but not gluten, elicit modest symptoms of IBS (Am J Clin Nutr 2022) · de Graaf et al., Expectancy versus actual gluten intake in non-coeliac gluten sensitivity (Lancet Gastroenterol Hepatol 2024) · Biesiekierski et al., Non-coeliac gluten sensitivity (Lancet 2025) · van Megen et al., A low FODMAP diet reduces symptoms in treated celiac patients with ongoing symptoms (Clin Gastroenterol Hepatol 2022) · DGVS, German S2k guideline on coeliac disease (2021) · Penny et al., BSG guidelines on the diagnosis and management of adult coeliac disease (Gut 2026) · Vasant et al., BSG guidelines on the management of IBS (Gut 2021) · Swiss Society for Nutrition (SGE), Fact sheet on nutrition and coeliac disease (2024) · Swiss Allergy Centre, Wheat allergy · German Federal Institute for Risk Assessment (BfR), Gluten and cereals containing gluten (2026) · Swiss ordinance on food information (LIV), Art. 41 · Health New Zealand, Low FODMAP Diet Phase 1 (2025) · FODZYME, Manufacturer information on fructans and gluten
