A gluten free diet is all the craze nowadays for irritable bowel syndrome (IBS)… because it does seem to help (at least, to a certain extent) in many cases, when it comes to symptom relief. But is gluten really the culprit of your IBS symptoms, or could it be fructans – or both?
According to the latest research, the majority of IBS sufferers who feel better on a gluten free diet may actually have a fructan intolerance – a subtype of FODMAP intolerance which masquerades as a non-celiac gluten sensitivity. (1, 2)
- In some cases, however, gluten may still be an issue – specifically for IBS sufferers who also have intestinal hyperpermeability, aka “leaky gut.” (3) This is a conversation for another time!
Another major caveat I’ve noticed is that my clients who don’t tolerate foods high in fructans still may not feel 100% relief on a low fructan diet. That’s because their fructan issues seem to go hand-in-hand with other types of FODMAP intolerances. (Think: lactose, fructose, polyols, etc.)
- TLDR: Even if you have a fructan intolerance, a low-fructan diet may still not be enough as a stand-alone intervention to relieve IBS symptoms.
When using a root-cause approach, IBS symptoms rarely – if ever – boil down to ONE food (or category of foods) – because foods don’t cause IBS!
I’ve learned (as a former IBS sufferer and gut health dietitian) that the root causes of IBS symptoms and food intolerances exist at deeper levels such as digestive insufficiency, microbial imbalance, and nervous system dysregulation.
Whether you’re someone who follows a gluten free diet for IBS (and aren’t getting 100% symptom relief), or you’re a clinician who’d like to support your patients with IBS more holistically from a nutrition standpoint, keep reading.
Let’s break down this whole fructan intolerance thing step-by-step!
Disclaimer: This article is educational and generalized. The information in this post should not replace medical/nutritional advice from your healthcare team. Consult with your healthcare providers 1-1 for customized advice tailored to your bio-individual needs.
Affiliate disclosure: This post contains affiliate links*. I may earn a commission on qualifying purchases at no extra cost to you!
Table of Contents
What are fructans?
Fructans are a type of fermentable short-chain carbohydrates which consist of a small number of individual fructose units conjoined together, with one glucose molecule at the end.
Examples of fructan molecules most commonly found in food are inulin, levanare and geraminan. (4)
From a molecular standpoint, fructans are categorized as a subtype of oligosaccharide, the “O” in FODMAP.
Foods high in fructans are restricted on a low FODMAP diet for IBS, because they’re poorly digested and thus highly fermentable in our small intestine, leading to IBS symptoms like gas, bloating and diarrhea. (4, 5)
What is a fructan intolerance?
A fructan intolerance (aka “fructan malabsorption”) means the fructans are not getting properly broken down, digested and absorbed in our intestines.
In this case, consuming foods high in fructans may trigger unwanted IBS symptoms.
Fructans and IBS
A 2024 study found that ~49% of 186 IBS sufferers tested positive for fructan malabsorption, according to hydrogen breath testing samples which were collected every 30 minutes for 3 hours following consumption of a 10-gram fructan solution. (6)
TLDR: Almost half of people with IBS and/or SIBO seem to have some degree of a fructan intolerance, and thus will feel sick after consuming high-fructan foods.
Fructan intolerance: signs and symptoms
In cases of a fructan intolerance, eating foods high in fructans will trigger some or all of the following symptoms:
- Abdominal pain
- Gas
- Bloating/distention
- Diarrhea
- Constipation (sometimes)
- Nausea, with or without vomiting
- Heartburn/reflux
- Indigestion
- Burping
That’s because these poorly digested food particles may feed microbes in our intestines, leading to fermentation and excessive gas production.
Much like lactose intolerance, undigested fructan particles entering our colon may also pull in excess water (by osmosis), leading to diarrhea, abdominal cramping, gas, bloat, and a sense of urgency to “evacuate”.
Another clue that you (or your clients) may have a fructan intolerance is feeling somewhat better on a gluten free diet, since the majority of foods that contain gluten also happen to be high in fructans.
Fructans in food: High and low fructan foods list
Foods high in fructans
Fruits
- Apricots
- Currants
- Figs
- Goji berries / “wolfberries”
- Grapefruit (1/2 cup or more)
- Medjool dates (more than 1)
- Nectarines
- Peaches
- Pears
- Plums
- Prunes
- Persimmons
- Raisins (more than 1 TBSP)
- Dried pineapple
- Pomegranate seeds (more than 2 TBSP)
- Watermelon
Veggies
- Artichokes
- Asparagus
- Beetroot
- Brussels sprouts
- Button mushrooms
- Savoy cabbage
- Okra (more than 7 pods)
- Onions
- Pumpkin
- Shallots
- Scallions (white parts)
- Snow peas (more than 23 pods or 3/4 cup)
Grains and starches
- Wheat (commonly found in regular bread, cereals, bagels, biscuits, buns, flour tortillas, flatbreads, pancakes, waffles, muffins, pastries – cookies, cakes, etc.; pasta, pizza, noodles, crackers, couscous, granola bars, and other all-purpose flour products)
- Wheat bran
- Barley
- Rye
Proteins (beans/legumes)
- Black beans
- Mung beans
- Split peas
- Red kidney beans
Nuts & seeds
- Cashews
- Pistachios
Herbs/spices
- Chamomile tea
- Fennel
- Garlic and garlic powder
Miscellaneous ingredients
- Inulin
- Chicory root
- Fructo-oligosaccharides (found in some prebiotic/probiotic supplements)
Low fructan foods
Fruit
-
- Strawberries
- Blueberries
- Raspberries
- Dried cranberries (2 TBSP or less per serving)
- Medjool date (up to 1)
- Naval orange (1 medium)
- Clementines (2)
- Pineapple, fresh (1 cup or less)
- Honeydew melon (1/2 cup or less)
- Cantaloupe (3/4 cup or less)
- Kiwi
- Banana (medium yellow, firm)
- Papaya (1 cup fresh)
- Dried banana chips (up to 15)
- Plantains (1/2 cup cooked)
- Starfruit
- Passionfruit (up to 2)
- Pomegranate seeds (up to 2 TBSP)
- Prickly pear
- Raisins (up to 1 TBSP)
- Avocado (high in healthy fat; contains persitol)
- Mango (contains fructose)
- Apples (contain fructose and sorbitol)
- Blackberries (contain sorbitol)
- Grapes (contain fructose)
- Cherries (contain fructose and sorbitol)
Veggies
- Bell peppers
- Bok choy
- Broccoli
- Celery (contains mannitol)
- Cauliflower (contains mannitol)
- Collard greens
- Cucumbers
- Hearts of palm (up to 1/2 cup)
- Jicama (up to 1/3 cup)
- Kale
- Lettuce
- Okra (7 pods or less)
- Oyster mushrooms
- Purple cauliflower
- Leafy greens
- Red cabbage (from 3/4 cup raw or less)
- Snow peas (up to 23 pods or 3/4 cup)
Grains/starches
- Sourdough bread (contains gluten)
- Sweet potatoes
- Regular potatoes
- Cassava flour
- Oats & oat flour(up to 1/2 cup)
- Rice
- Quinoa
- Corn
- Polenta
- Grits
Proteins
- Beef (ground, steak)
- Eggs
- Chicken
- Turkey
- Fish/seafood
- Pork
- Tofu, firm (up to 1 cup)
- Cheese
- Cottage cheese
- Yogurt (may contain lactose and/or fructose unless plain, lactose free)
- Chickpeas (contain GOS if more than 1/4 cup canned)
Note: Any of the above proteins seasoned with sauces or herb/spice blends containing garlic/onions are not low in fructans.
Nuts & seeds
- Almonds
- Walnuts
- Hazelnuts
- Chestnuts
- Pecans
- Brazil nuts
- Sunflower seeds
- Pumpkin seeds
Herbs/spices
- Basil
- Cacao
- Coriander
- Chives
- Curry
- Dill
- Fenugreek
- Herbs de Provence
- Gotu kola
- Ginger
- Marjoram
- Sage
- Parsley (1 teaspoon, dried)
- Rosemary (1 teaspoon, dried)
- Tarragon (1 teaspoon, dried)
- Peppermint
- Thyme (1 teaspoon, dried)
- Bay leaves
- Oregano
- Turmeric
- Lemongrass
- Hibiscus
How to know if you have a fructan intolerance
If you feel better on a gluten free diet but you don’t have celiac disease, and/or you DO have celiac disease but aren’t finding 100% relief on a gluten free diet, there are a few different ways to determine whether or not you have a fructan intolerance.
Lab testing
The most clear and direct method is to run a hydrogen breath test, where breath samples are taken every 15 to 30 minutes for 3 hours after consuming a fructan solution.
(If breath gases are high, it indicates fructan malabsorption.)
Low FODMAP elimination and reintroduction diet
As I mentioned earlier, the majority of folks with a fructan intolerance also seem to have at least one or more other types of FODMAP intolerances.
That being said, you may benefit from a 6 to 8-week low FODMAP elimination and reintroduction diet (with guidance and clinical supervision from a FODMAP-trained gut health dietitian), if you have a healthy relationship with food.
Switch to sourdough
I’ll be frank – nailing down your food-symptom triggers is not always a straight-forward, cookie-cutter process. It often takes some trial, observation, and detective work!
For example, if you’d like to determine whether it’s fructans versus gluten and/or wheat, as culprit(s) of your IBS symptoms, consider integrating sourdough bread (a type of low fructan, low FODMAP bread which contains wheat and gluten) into your low FODMAP diet.
How it works: If you feel sick after eating this wheat and gluten-containing grain, then gluten and/or wheat may be linked with your gut issues.
- This was the case for me, as someone with a non-celiac WHEAT sensitivity but still able to eat other types of foods containing both gluten and fructans – such as rye and barley!)
Keep a detailed food-symptom journal
Tracking your food intake and symptoms will make the detective work (in terms of uncovering your food-symptom triggers) a whole lot easier for you!
Recommended reading: Why & How to Keep an IBS Food Diary
Try out fructan enzymes
Alternatively, if you are prone to disordered eating and/or unintentional weight loss, dietary restriction may not be the best path to better health.
Trying a fructan-specific digestive enzyme (such as FODZYME* or FODMATE) with higher FODMAP foods may help to reduce symptoms associated with fructan intolerance as well as other potential FODMAP intolerances.
- Enter my affiliate code WHOLEISTICLIVING for 15% off your FODZYME order!
(However, results vary and more research is needed when it comes to enzyme replacement therapy for fructans! When in doubt, listen to your body, take what works and leave the rest. And of course always consult with your treatment team!)
Frequently asked questions (FAQ’s)
Are fructans bad for you?
Fructans aren’t inherently bad for us. In fact these fermentable carbohydrates have even been shown to have prebiotic activity in a healthy gut.
More specifically, fructans seem to increase the abundance of healthy probiotic microbes such as Lactobacillus spp. and Bifidobacterium spp. (7, 8)
However, if you have IBS or SIBO, you may be more prone to having a fructan intolerance and may experience a negative reaction to foods high in fructans.
What are the best fructan digestive enzymes on the market?
Based on my own experience and research, FODZYME (powder) and FODMATE (capsules) are the best fructan digestive enzymes worth trying.
An added benefit of these is they also help digest and break down other types of FODMAPs.
Fructans vs. gluten – what’s the difference?
From a molecular standpoint, fructans are carbohydrates while gluten is a type of protein.
Some of the food sources of fructans vs. gluten share some overlap and similarities, but they aren’t all the same.
For example, both fructans and gluten are found in certain types of grains: wheat, barley, rye, and oats.
However, fructans are not exclusively found in those grains. Fructans are also found in many other types of plant foods (such as fruits, veggies, gluten free grains, nuts, beans, and even some herbs), depending on the serving size.
Fructans vs. fructose – what’s the difference?
Fructose is a type of monosaccharide (single-unit sugar molecule similar to glucose), while fructans are made up of chains of fructose ranging from 2 to 60 fructose molecules per each fructan molecule.
The food sources of fructans are also mostly different from food sources of fructose, although there’s some overlap. (For example, a medium pear contains both fructose and fructans.)
Many people with a fructan intolerance may also have a fructose intolerance, although this isn’t always the case.
Related articles
- What are Polyols? Exploring the “P” in FODMAP
- When Is Oatmeal Low FODMAP?
- Beans and IBS: Expert Advice on Enjoying Low FODMAP Beans & Legumes
- Lactose Intolerance vs. Dairy Sensitivity: How to Tell Them Apart
- Wheat vs. Gluten – What’s the Difference?
- What’s the Best IBS Diet for You? (Expert Guidance)
Recap & final thoughts
A fructan intolerance (aka fructan malabsorption) will cause you to experience IBS symptoms such as gas, bloating, abdominal pain, constipation, and/or diarrhea after consuming foods high in fructans.
That’s because the undigested food particles will ferment with microbes when they enter our intestines, producing gases as a bi-product.
Fructan intolerance often gets mis-labeled as a non-celiac gluten sensitivity/intolerance, because the majority of gluten-containing foods are also high in fructans. This is one reason why so many IBS sufferers feel better on a gluten free diet.
Approximately ~50% of IBS sufferers may have a fructan intolerance, according to research.
The caveat is that a low fructan diet may not be enough to resolve IBS symptoms, since so many people who don’t tolerate fructans will have at least one additional type of food intolerance (usually in the form of a FODMAP intolerance).
In addition to keeping a detailed food-symptom journal (such as an IBS food diary), a fructan malabsorption test, low FODMAP elimination & reintroduction diet, and/or fructan enzymes can help you to identify or rule out a fructan intolerance.
As always, make sure to listen to your body and consult with your healthcare providers when in doubt! 😉
Next steps
Did you find this helpful? Would you like to continue learning about how to navigate IBS symptoms and food intolerances holistically? If so, make sure to download our free comprehensive low FODMAP foods list PDF here!
Wishing you all the best,
XX – Jenna
