Gluten vs Fructans: which is your trigger?


While a gluten free diet can help with digestive troubles, the elimination of gluten may not be what’s actually leading to relief. Read on to learn more about this counterintuitive phenomenon.

A gluten free diet can simultaneously be low in a complex carbohydrate called fructans. Let’s dive into how to identify whether gluten or fructans are likely troublesome for you and whether you may be able to add gluten back to your diet if you’re currently avoiding it.

Gluten vs Fructans

Gluten and fructan-rich foods differ in several ways.

What is gluten?

Gluten is a protein found in wheat, barley, and rye. In a gluten free diet, all sources of gluten, which includes foods like bread, pasta, cereal, baked goods, and other products containing wheat, barley, or rye, are avoided.

A gluten free diet is essential for those with gluten intolerance or celiac disease, non-celiac wheat sensitivity or wheat allergies. Note that non-celiac wheat sensitivity may also be described as gluten sensitivity or non celiac gluten sensitivity.

What are fructans?

Fructans are a type of FODMAP; complex carbohydrates that are poorly digested and often cause digestive symptoms when they reach the large intestine, especially in those with irritable bowel syndrome.

The term “FODMAP” is an acronym that stands for Fermentable, Oligosaccharides, Disaccharides, Monosaccharides, And Polyols. Fructans are part of the oligosaccharide (‘O’) group which, when broken down (i.e. fermented) by gut bacteria in the large intestine, produce gas and other common gastrointestinal symptoms.

Fructans are present in gluten-containing grains like wheat, barley and rye, as well as many other plant foods, like fruits, vegetables and additional grains. Garlic, onion, leeks, scallion, shallot, asparagus, brussels sprouts, pomegranate and banana are all particularly high in fructans.

Differences between gluten diseases and fructan intolerance

Anyone diagnosed with celiac disease, non-celiac wheat sensitivity or wheat allergies must follow a gluten free diet. When those with celiac disease consume the gluten protein, even in small amounts, it triggers an autoimmune response that damages the absorptive capacity of the small intestine.

Wheat allergy does not directly damage the intestine in the same way, but does also trigger an immune response, which can occur within minutes to days following ingestion of the gluten protein. Roughly 1% of the US population has celiac disease, while the prevalence of wheat-based food allergy is likely in the range of 0.2% to 1%.

The mechanism behind non-celiac wheat sensitivity is less understood, but also triggers digestive and sometimes systemic symptoms. Because of the lack of extended epidemiological studies, the reported prevalence of non-celiac wheat sensitivity varies greatly from 1% to 13%.

Diagnosing fructan intolerance

There is no formal way to diagnose fructan intolerance. An estimated 10-15% of the global population has irritable bowel syndrome, though many more may not have received a formal diagnosis but meet the diagnostic criteria. About three quarters of those with irritable bowel syndrome are sensitive to FODMAPs, like fructans.

The low FODMAP diet is a 3 step process developed by Monash University used to help identify triggers of digestive distress and manage the symptoms of irritable bowel syndrome. The diet includes the elimination phase, personalization phase, and the reintroduction phase.

Many FODMAPs, including fructan rich foods, provide benefits for digestive health, so the aim of the low FODMAP diet is to identify the high FODMAP foods and their amounts that cause digestive symptoms and then add back in foods that are well tolerated. Among those who find they do have FODMAP intolerances, tolerance thresholds will vary greatly.

Should you avoid gluten or fructan?

The overlap between gluten-containing foods and high FODMAP foods lies with the grains wheat, rye, and barley, all of which contain both gluten and fructans.

Is gluten free also fructan free?

Switching to a gluten free diet often also tends to be lower in fructans. Remember, gluten free foods are often recommended on the low FODMAP diet as they remove wheat, rye, and barley, but this also significantly reduces intake of fructans. In turn, the reduction in gluten also indirectly leads to a reduction in the overall FODMAP burden in the digestive system.

However, fructans are found in far more foods than just wheat, rye and barley. This fact can provide clues toward whether gluten or fructans are causing symptoms. Once an irritable bowel syndrome diagnosis is made and other gluten-related diseases are ruled out, consider whether a gluten free diet is helping with gastrointestinal symptoms due to the elimination of gluten or due to the reduction in fructans.

Fructan might be your trigger if:

Fructan intolerance may be the cause of your symptoms if you find gluten free foods like garlic, onion, Brussels sprouts, savoy cabbage and grapefruit triggering. These are are all high-fructan yet gluten-free foods, so digestive symptoms related to any of these may point toward fructan intolerance.

High-FODMAP, gluten-free foods:

  • Fruits: Cranberry, dried currant, Medjool dates, dried fig, grapefruit, pomegranate, ripe banana
  • Vegetables: Artichoke, asparagus, raw beet, Brussels sprouts, fennel, garlic, white parts of leek, all onion, pea, pumpkin, savoy cabbage, white parts of scallion, shallot
  • Grains: Amaranth, chickpea flour & products, soy flour & products
  • Other: Almonds & almond butter, most beans, cashews, lentils, oats or oat bran in large portions, pistachios, silken tofu

Gluten free alternatives: the inulin factor

Several gluten free alternatives, like pizza crusts, dried pasta and cookies, are considered low FODMAP foods, but not all gluten free products are automatically low in fructans or FODMAPs. High FODMAP ingredients are often lurking in gluten free certified products.

For example, many gluten free products are often low in fiber. To counter this, manufacturers might add inulin (chicory root extract), apple fiber, fructo-oligosaccharides (FOS), oligofructose, or other high FODMAP fiber sources to increase their nutritional value.

Plus, several flours are gluten free but not low FODMAP. For example, soy flour, coconut flour, and chickpea flour are all high FODMAP. Apps like Spoonful can help determine whether a gluten free flour is high or low FODMAP.

Bread in the gluten free diet and low FODMAP diet

Globally, bread is a major dietary source of fructans. Some artisan bakery breads have a significantly low gluten content but are high in fructans.

A 2011 study reported that some brands of gluten free bread might contain the same amount of fructans (1 g/100 g) as regular bread. While some gluten free breads may be low FODMAP (0.1 g fructan/slice), some may be very high FODMAP (0.55 g fructan/slice).

Another, more recent study, also points toward the wide range of gluten and fructan content in breads.

What about sourdough bread?

Sourdough bread is often well tolerated among those sensitive to fructans. During sourdough fermentation, bacteria and yeasts break down fructans, thus reducing fructan levels in the final product.

Additional signs of fructan intolerance

If you’re able to tolerate real, authentic sourdough bread made from wheat flour, this indicates that fructans, rather than gluten, may be a digestive trigger. However, make sure to base your assessment using sourdough bread made with traditional fermentation techniques, which include an extended fermentation period.

Many mass-produced sourdough products use a condensed baking process that skips or shortens the fermentation and therefore does not reduce fructan content. High-FODMAP breads that market themselves as sourdough but were not made with traditional fermentation techniques will likely not be tolerated and are not helpful to learn if fructans are driving symptoms.

How to know if gluten is your trigger

If you’ve received a diagnosis of gluten intolerance, celiac disease, non-celiac wheat sensitivity or wheat allergy, your doctor will provide guidance on whether a gluten-free or wheat-free diet is necessary. If you tolerate the high-FODMAP, gluten-free fruits, vegetables and whole grains listed above, this is good evidence gluten is your trigger and you might want to raise concerns around a gluten-related condition with your medical provider.

Note that lactose intolerance may occur with poorly managed gluten-related conditions. This is because damage to the intestinal lining from consumption of gluten may cause a temporary reduction in the enzyme that breaks down lactose, called lactase. With implementation of a gluten-free diet and intestinal healing, lactose intolerance can generally be reversed.

How to decide to eat gluten free or low FODMAP

To summarize, not all gluten free products are low FODMAP foods. Just because a product says it is gluten free does not mean it is low FODMAP or that it will be well tolerated. Check for low FODMAP certified products using an app like Spoonful if you’re in doubt when trying new products.

Following an overly restrictive diet can be time consuming, expensive and frankly no fun. A gluten free diet can mean cutting out lots of delicious, whole grain foods, while a low FODMAP diet can lead to fewer fruits and vegetables on your plate. Both a gluten free diet and low FODMAP diet can be low in fiber and many important nutrients.

These drawbacks mean it’s important to work with a Registered Dietitian to understand your digestive triggers so you know what foods to avoid to manage symptoms – and what you can add back!

How to enjoy fructan foods

If you find that wheat, garlic, onions, asparagus, Brussels sprouts and more are causing digestive issues, fructans (not gluten) may be the culprit. One option is to avoid or limit your intake of these fructan foods based on your tolerance level.

Another way to manage the gut distress related to fructan intolerance is to target the troublesome fructans (and other FODMAPs) using a digestive enzyme, so you don’t have to limit your diet.

Managing FODMAPs

Digestive enzymes target and break down FODMAP triggers so that they cause less gut distress as the food passes through the digestive tract.

For example, FODZYME® is a digestive enzyme and a particularly helpful tool to manage FODMAPs and find relief from digestive discomfort. When sprinkled on a meal, FODZYME® breaks down the FODMAPs fructan, GOS, and lactose into simple carbohydrates that are easily absorbed in the small intestine.

This reduces the amount of FODMAPs in the gut by targeting FODMAPs directly, turning high FODMAP meals into low FODMAP ones. Using a digestive enzyme can help reduce stress around food choice, enable more food freedom and allow for a more nutrient-rich diet.

New Research on gluten and FODMAPs

It’s important to note that gluten and FODMAP research is ongoing. For instance, a new study found that while buckwheat is gluten free and currently considered low FODMAP, it might be a trigger for some due to its fagopyritol content.

In essence, though both gluten free and low FODMAP diets aim to reduce digestive discomfort, they serve different needs and aren’t interchangeable. An individualized approach is important to understand which is right for you.

Join the Conversation

  1. My son was recently diagnosed with fructose intolerance, so I find this article very informative. We have yet to find out what the trigger factor is which leads to “flare up” as he has months where he can tolerate any amount of sweet foods then he may start to get tummy pains & upset.

    1. Hey Jay – thanks for writing! Just a heads up that this article covered “fructans” vs “fructose”. These are both elements of the FODMAP acronym but involve different foods.

  2. I’m lactose intolerance and I am still having stomach issues , it seems like I have some of the fructan issues, I was wondering if the food Ap would work for me.

    1. Hey Cindy – the Low FODMAP diet might be worth a shot if you suspect fructans are the culprit. Here’s an article we wrote that covers the basics on how to get started:

      If possible, always work with a medical professional when doing this diet as it can be quite restrictive.

  3. Carolyn Huffman says:

    Where can I obtain FODZYME?

    1. Hey Carolyn – you can pick some up via their website – Hope this helps!

  4. I’ve found that true sough dough works for me and the best way I’ve found to guess whether it’s the real thing is to look for yeast in the ingredient list.
    I’m curious what is known about whether other fermented foods- kombucha, sauerkraut, beer, wine- are helpful in IBS?

    1. Hi Debbie!
      I’m so glad you’re a true sourdough detective now! You bet: if we see flour, salt and water (sometimes “sourdough starter” is listed too) then we are more likely getting the real deal.

      As for fermented foods and their impact on someone’s IBS, my answer would be “it depends”.

      In general, these foods and beverages may fit into someone’s diet, and contain novel chemicals that are only found in fermented foods.

      Beer and wine (and alcohol in general) however, may be gut irritants/triggers for some folks with IBS.

      Sauerkraut, may be fine for some with IBS, however if one’s triggers include the FODMAP subgroup mannitol (like yours truly), which sauerkraut is high in, then this food may trigger symptoms.

      Kombucha may vary in its ingredients, and this may be variable in terms of FODMAPs, for example. So with foods and beverages like this, it might be worthwhile to scan on the Spoonful app, or, try a small amount and monitor for any symptoms.

      So, to sum, it is highly individual, the way that fermented foods may or may not fit well into someone with IBS’s diet.

      Best thing would be to work with a Dietitian to include the most variety possible, while balancing symptoms and any other health goals one may have.

      I hope that helps!



      I hope that

  5. Lori Jablonowski says:

    I am 62 and have been dealing with IBS and GERD for most of my adult life. I have been to many gastroenterologists over the years and have learned more from websites than from the doctors. I believe my biggest triggers are Fructans and Lactose and follow the FODMAP diet. Biggest triggers are onion and garlic and some dairy products. I get very frustrated with symptoms still occurring even on a very limited diet. I have never been “tested” for food sensitivities or intolerances and wonder what you would recommend. I have never been to registered dietitian. I have looked into the Fodzyme product but afraid to try it because if I eat something with garlic or onion and the powder doesn’t work then my stomach will go crazy and I want to avsid an episode at all cost. Any suggestions?

    1. Hi Lori,

      As a person with IBS-D herself, I can 100% understand, intimately, where you are coming from when you say you try to avoid an episode at all costs. I’ll try my best to summarize my thoughts below, and hopefully it’ll help guide you for next steps:

      Food intolerance/sensitivity testing: Unfortunately there are no (science-based) tests that can give the whole picture on someone’s food sensitivities or triggers.

      There are lactose breath tests that can be helpful, for identifying lactose intolerance for example. Also, I always recommend someone is screened for Celiac Disease/IBD (every couple of years, or if symptoms seem to change or worsen suddenly, in particular). These are blood tests (for Celiac Disease, called an IgA-tTg) and blood & stool, and possible scopes, to screen for IBD, typically. Your doctor might recommend scopes, imaging or other tests as well based on one’s age and family history.

      The next thing I would say is that investing in a Registered Dietitian who focuses on IBS in their practice would probably be very worthwhile. In the Monash app or website there is a Dietitian Directory and you can search by Country, State/Province to find one near you. These Dietitians have undertaken special training in serving clients/patients with IBS.

      As for FODZYME, I use this in my life when I know I’m eating a food that contains fructans (one of my most problematic triggers). It has sound science behind it. Always, of course, we want to ensure we loop in our doctor or pharmacist before making any dietary or supplement changes.

      Lastly, I always remind folks that they may have additional layers to their story, like SIBO, or Histamine intolerances for instance.

      Also, in my practice I’ve found that taking a IBS-subtype specific approach helpful. For instance, the steps I recommend for IBS-D (diarrhea-predominant IBS) can be markedly different than the steps I might give clients with IBS-C (constipation-predominant IBS).

      I have a library of free resources for each subtype of IBS (D, C, M, U) on my website, available for anyone to download.

      I hope this helps.


  6. Very, Very helpful article, thank you. I have been dealing with IBS – D for over 4 years since a sports related concussion. It started as IBS – C, turned into Methane Positive SIBO and it’s been super IBS – D for a long time now. I have gone various routes over the years, following FODMAP (or trying) and it’s been a very stressful, frustrating up & down journey. Especially when I don’t eat anything that I know will trigger me (like garlic/onion/wheat) and then I get bloated/low energy/stomach pains/constipated etc. I’ve gained weight I cannot drop, despite eating low calories & being very active. I started seeing a natural medicine practitioner about a year ago and it’s been helpful, but quite costly and it’s a long process of figuring stuff things out, but she HAS helped me balance my gut bacteria better so I pray that I’m on my way to feeling better. I have never gotten to the “re-introduction phase” after trying to eat fodmap for 4 years. This article was very helpful in breaking down a few things and especially more detailed info about Fructans. I will ask her about the FODZYME, especially since I travel & sometimes it’s impossible not to eat out and I never know what is really in my food (spices) despite my “dietary requests” when I order.

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