Have you ever noticed that your irritable bowel syndrome (IBS) symptoms seem to get worse after eating wheat (or products with wheat ingredients)? While many people attribute their gastrointestinal symptoms to gluten sensitivity after trialling a gluten-free diet and experiencing symptom relief, gluten isn’t always the culprit.
Instead, another component of wheat products, called fructans, may be to blame for digestive symptoms like gas, bloating, abdominal pain, and unpredictable bowel movements. This article will teach you the difference between gluten and fructans, how FODMAPs can trigger digestive symptoms in people with IBS, and how to identify whether you need a gluten-free diet or a low-fructan diet.
What Is Gluten?
Gluten is a protein found in wheat, barley, and rye. In food, gluten helps provide structure, elasticity, and chewiness, making it an extremely important ingredient in baked goods. Wheat flour is the primary source of gluten in most baked goods, and both gluten and other food components in wheat flour can impact digestive health.
It’s typically recommended to use higher-gluten flour when you want structure and chew (think artisan breads, bagels, and chewy sandwich loaves) and lower-gluten flour when you want tenderness and softness (think cakes, muffins, and cookies). For home bakers, all-purpose flour offers a good middle ground and can be used to make a variety of everyday baked goods.
Many people report worsening digestive problems after eating foods with gluten, but emerging research suggests it may be the fructans (a type of carbohydrate) in wheat, barley, and rye that cause symptoms, not the gluten.
This is because gluten is not considered a FODMAP (which we’ll discuss in a minute). As such, it’s not fermented in the gut. While gluten can cause problems for some people—especially those with celiac disease or gluten sensitivity—in IBS, symptoms are more often triggered by FODMAPs like fructans rather than gluten.
What Are FODMAPs?
Unlike gluten, FODMAPs are a type of carbohydrate. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, which are poorly absorbed short-chain carbohydrates.
There are five FODMAP categories:
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Fructans (one type of oligosaccharide)
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Galacto-oligosaccharides (GOS, another type of oligosaccharide)
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Lactose (a disaccharide)
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Excess fructose (a monosaccharide)
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Polyols (specifically, sorbitol and mannitol)
The reason FODMAPs matter in IBS symptom development is because of how they act once they reach the large intestine. Because FODMAPs are poorly absorbed, they resist digestion in the small intestine and arrive at the large intestine intact. Here, your gut bacteria ferment them, producing gas.
In healthy individuals, this fermentation process usually does not cause significant symptoms, but in people with IBS, who have visceral hypersensitivity or extra-sensitive digestive organs, normal digestive processes—like gas production after FODMAP fermentation—can be extremely painful, as the gas puts pressure on the extra-sensitive colon walls.
Additionally, certain FODMAPs have an osmotic effect. This means they draw water into the colon, which can result in gastrointestinal symptoms such as changes in bowel frequency and stool consistency (e.g., diarrhea).
So how do FODMAPs relate to wheat and IBS symptoms? Wheat, barley, and rye contain a FODMAP called fructans. Studies show that around 25% of people with IBS have fructan intolerance and experience symptoms when they eat fructan-containing foods. This occurs because humans lack the enzymes needed to digest fructans, so fructans get rapidly fermented by your gut bacteria (which, as you’ll recall, leads to gas production). This intolerance to FODMAPs is a form of food intolerance.
The end result is that high-fructan, gluten-containing foods such as wheat, rye, and barley can all cause uncomfortable digestive symptoms like gas, bloating, and abdominal pain in people with IBS. The low FODMAP diet (which involves dietary reduction of high FODMAP foods for a short amount of time) has been clinically proven to reduce symptoms in around three-quarters of individuals with IBS.
Gluten vs. FODMAPs: Why Wheat Is Often Misunderstood
While gluten (protein) and fructans (carbohydrate) are both found in wheat, rye, and barley, gluten is the better-known component of the two. However, their impact on the body is very different.
Gluten triggers an autoimmune reaction in people with celiac disease, leading to intestinal damage. While this can trigger digestive symptoms such as gas, bloating, abdominal pain, and diarrhea, it often also involves other symptoms, including weight loss, iron-deficiency anemia, and joint pain. People with celiac disease must follow a strict gluten-free diet to prevent further intestinal damage.
In contrast, high fructan foods trigger digestive symptoms due to gas production from bacterial fermentation. While the resulting gas and bloating can be extremely painful, they don’t damage the digestive tract. However, unlike gluten (which must be completely eliminated for people with celiac disease), not everyone with IBS needs to avoid fructans, and some people can tolerate fructans in smaller portions.
So, why do so many people experience symptoms when eating a gluten-containing diet, but feel better when they follow a gluten-free diet? Because by reducing the amount of high-gluten foods in their diet, they’re also typically lowering their fructan intake. Individuals with IBS often report improvement in overall symptoms like recurrent abdominal pain and bloating when following a gluten-free diet, but this may be due to the reduction of FODMAPs rather than gluten itself.
Curious about which grain-based foods are high and low FODMAP? Here’s a quick breakdown:
IBS and Gluten-Related Disorders
While IBS and gluten-related disorders like celiac disease and non-celiac gluten sensitivity (NCGS) have some overlap in symptoms, they differ in how and why they cause symptoms.
IBS is classified as a disorder of gut-brain interaction (previously called a functional gastrointestinal disorder). This means that it isn’t caused by anything structurally wrong with the digestive tract, but instead by a miscommunication between the gut and the brain. This miscommunication can lead to changes in pain perception and gut motility. While many factors can influence IBS symptoms, high FODMAP foods are a key trigger.
Then we have NCGS, also known as non-celiac wheat sensitivity (NCWS). This is a lesser-known condition in which a person develops similar symptoms to celiac disease, such as abdominal pain, bloating, brain fog, and joint pain after eating wheat or other gluten-containing foods, which resolve with gluten withdrawal from the diet.
However, people with NCWS test negative for celiac disease and wheat allergy. While we’re still learning about the cause of NCWS, potential mechanisms include changes in gut barrier integrity, gut microbiota dysbiosis (an imbalance between beneficial and harmful gut microbes), immune system activation, and abnormal immune responses to food antigens such as gluten and amylase-trypsin inhibitors (ATIs). Diagnosis is challenging because we don’t currently have diagnostic tests for NCWS. Therefore, it is typically diagnosed only after celiac disease and wheat allergy have been ruled out, and when removing gluten (but not fructans) from the diet leads to symptom resolution.
Finally, we have celiac disease. Affecting about 1% of people worldwide (including about 2 million people in the United States), celiac disease is an autoimmune condition that results from an immune reaction to gluten. In celiac disease patients, the immune system mistakenly attacks the small intestinal lining, damaging the small, fingerlike projections called microvilli. This leads to poor nutrient absorption and gastrointestinal symptoms (especially abdominal pain, bloating, and diarrhea), anemia, fatigue, weight loss, and more. The only treatment is a lifelong gluten-free diet.
Since wheat is one of the highest sources of fructans in Western diets, many people mistake fructan-related symptoms for those related to wheat or gluten.
Do I Need a Low FODMAP Diet or a Gluten-Free Diet?
When deciding whether you need a low FODMAP diet or a gluten-free diet, an accurate diagnosis is critical. Since celiac disease can only be diagnosed if a person has been consuming gluten-containing products, it’s important not to start a gluten-free or low FODMAP diet until you’ve been tested for celiac disease. The screening process for celiac disease typically involves a blood test to detect specific antibodies (immune cells) and an intestinal biopsy to assess damage to the microvilli.
When considering dietary interventions, controlled trials—including double-blind studies—have shown that a gluten-free diet can lead to symptom relief in a subset of IBS patients, but results vary widely. Additionally, some research suggests that a person's expectation of eating gluten, combined with actually eating it, seemed to have the biggest impact on gut symptoms. This suggests that in some cases, symptoms may be due to a nocebo effect (feeling worse because you expect to), although gluten itself may still play a role for some people.
Regardless of whether you have celiac disease, NCWS, or IBS, it's recommended to work with a dietitian to ensure you get the nutrients you need while following a restrictive diet.
When a Low FODMAP Diet Makes Sense
A low FODMAP diet is best for people with IBS who experience symptoms such as bloating, gas, abdominal pain, or changes in bowel movements after eating high FODMAP foods ( including wheat, onion, garlic, dairy, and legumes).
The low FODMAP diet is made up of three distinct phases:
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Elimination: During the initial elimination phase (typically 2 to 6 weeks), you will replace high FODMAP foods with lower FODMAP alternatives. This phase helps you see whether FODMAPs as a whole are triggers while allowing you to get your symptoms under control.
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Reintroduction: During the reintroduction phase, you’ll reintroduce foods one FODMAP category at a time to see which specific FODMAP groups are triggers, as well as which portion sizes you can tolerate. This phase is critical to ensuring you’re restricting as few foods as possible long-term.
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Personalization: Once you’ve reintroduced the different FODMAP categories and determined your personal triggers and thresholds, you’ll include the FODMAP groups that didn’t trigger symptoms in your diet while reducing your intake of the FODMAP categories that did trigger symptoms. During this phase, digestive enzymes that break down the FODMAPs you were sensitive to can be a useful way to further expand your diet and reduce anxiety about eating higher-FODMAP foods.
Remember, the goal of the low FODMAP diet is not to restrict yourself long-term. Instead, it’s about finding your personal triggers and tolerance levels so you can eat as varied a diet as possible while managing your symptoms. Plus, just because something is gluten-free doesn't mean it's the healthiest choice. Research shows that nutrient deficiencies (such as zinc and vitamin D) are common in people following a gluten-free diet.
When a Gluten-Free Diet Is Necessary
If you’ve been diagnosed with celiac disease, it is essential to avoid gluten-containing foods such as wheat, barley, and rye to prevent damage to your small intestines and manage symptoms. A gluten-free diet can also be trialled for people with suspected NCWS.
It’s important to note that gluten-free does not automatically mean a food is also low FODMAP. While many gluten-free foods are low in fructans, they may contain other high FODMAP ingredients. For example, while a corn tortilla is considered both gluten-free and low FODMAP, the beans and sour cream you may add to a burrito are high in GOS and lactose and may trigger symptoms. Additionally, certain gluten-free flours (such as oat, chickpea, and coconut flours) are high in FODMAPs. It’s important to look at the meal as a whole to ensure it is low in the FODMAPs you’re sensitive to.
Additionally, stress can play a huge role in the development of IBS symptoms. This is because stress and anxiety can impact gut motility and pain perception, leading to symptoms even if you’ve been avoiding high FODMAP foods.
While eating a gluten-free diet may provide symptom relief, it doesn’t prove that gluten was the issue. If you’re sensitive to fructans, following a gluten-free diet may have helped improve your symptoms due to the reduced fructan load—not the reduction in gluten.
Using FODZYME With Gluten-Containing Foods
At the end of the day, determining whether gluten vs. FODMAPs are responsible for your symptoms requires an accurate diagnosis of celiac disease, NGWS, or IBS. Once you know the cause of your symptoms, you can decide whether a low FODMAP diet or a gluten-free diet is a better option for you.
If you’ve determined that the fructans found in wheat-based products trigger your symptoms but you don’t want to avoid those foods forever, a digestive enzyme supplement can help. FODZYME contains three digestive enzymes that break down fructans, GOS, and lactose before fermentation. This can help reduce bloating and gas from wheat-based meals, help maintain dietary flexibility, and reduce anxiety around shared or restaurant meals.
However, while FODZYME can be used as a supportive tool, ongoing symptoms that interfere with your daily life, as well as symptoms like bloody stools, persistent vomiting, or unintentional weight loss, should all be evaluated by a medical professional to ensure they’re not being caused by something other than IBS.
If you have IBS and struggle with fructan intolerance, try FODZYME today and enjoy foods like bread and pasta without worrying about them causing uncomfortable symptoms.
IBS and Gluten FAQ
Does Gluten Trigger Symptoms in Individuals with IBS?
No, gluten does not trigger symptoms in people with IBS unless they also have celiac disease. It's typically the fructans (a type of FODMAP) in wheat, rye, and barley-based foods that trigger IBS symptoms. People with IBS often experience symptom relief when following a gluten-free diet because of the reduction in fructans, not gluten.
What Are the Worst Foods for IBS?
While everyone with IBS has different triggers, some of the most common include wheat, onions, garlic, legumes, lactose-containing dairy products, and meals containing multiple types of FODMAPs.
How Do I Know If I Have Celiac or FODMAP Intolerance?
Here are the steps for determining whether you have celiac disease or FODMAP intolerance:
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Get tested for celiac disease, which typically includes a blood test and biopsy of the small intestine. If you test positive for celiac disease, you will need to follow a lifelong gluten-free diet.
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If you test negative for celiac disease, consider a short-term (2 to 6 weeks) low FODMAP diet.
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After 2 to 6 weeks of elimination, reintroduce foods one FODMAP category at a time to see which (if any) you're sensitive to, as well as which portion sizes you can tolerate.
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Track your symptoms across time and different portion sizes. This can help you determine whether you can tolerate small amounts of certain high FODMAP foods. It can also teach you about the relationship between your gastrointestinal symptoms and non-FODMAP triggers such as stress, lack of sleep, caffeine, and high-fat foods.
Is Wheat the Same as Gluten?
Gluten is one component of wheat. Wheat contains gluten (a protein) and fructans (a carbohydrate). Gluten can trigger symptoms in people with celiac disease or non-celiac wheat sensitivity (NCWS), while fructans can trigger gastrointestinal symptoms in people with IBS who have fructan intolerance.
Can IBS Symptoms Change Over Time?
Yes, IBS symptoms can change over time. Stress levels, sleep quality, microbiome health, and dietary patterns can all affect your gut's sensitivity and how well you tolerate certain foods. Keeping a food and symptom journal can help you determine links between these factors and your symptoms.