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Fructans may be responsible for your IBS symptoms

Irritable Bowel Syndrome (IBS) is a condition that is very common and affects 15% population worldwide. Since we don’t know what exactly causing the development of IBS, there is no cure. The only way people can control their symptoms is by finding their individual triggers and prevent the onset of flare ups. This can be done through diet and lifestyle changes.  Low FODMAP diet has been studied extensively with clinical research to back up its effectiveness in managing IBS. It involves limiting high FODMAP foods which may cause adverse reactions in the gut. You can read about a low FODMAP diet here.  

One of the subgroups on a low FODMAP diet that should be tested for tolerance is fructans.  Fructans are carbohydrates found in cereal grain, fruits, and vegetables and are made up of fructose units with glucose at the end.

There are 2 types of fructans: short chain and long chain. Short chain fructans consist of 2-10 fructose units and are called fructo-oligosaccharides (FOS) whereas long chains contain more than 10 fructose units and are called inulin.  

Here is the list of foods where fructans are found:

Cereal grains

  • Barley
  • Rye
  • Wheat
  • Bulgur
  • Couscous
  • Farina
  • Kamut
  • Spelt
  • Einkorn ⠀⠀⠀⠀⠀⠀
  • Emmer⠀⠀⠀⠀⠀⠀⠀⠀⠀
  • Farro⠀⠀⠀⠀⠀⠀⠀⠀⠀
  • Freekeh⠀

Baked goods

  • Any products that have wheat flour added
  • Pasta
  • Crackers
  • Cookies
  • Cakes
  • Muffins
  • Bagels
  • Pizza
  • Burger buns
  • Flour tortillas


  • Ripe banana
  • Grapefruit
  • Plum
  • Peach
  • Persimmon
  • Pomegranate
  • Nectarine
  • Watermelon


  • Asparagus
  • Beetroot
  • Brussel’s sprouts
  • White daikon
  • Jerusalem artichoke
  • Chicory root
  • Garlic
  • Onions

Humans lack the enzyme needed to break down fructan to single units to be absorbed. So, it travels to the large intestine where it is fermented by bacteria leading to prolifereation of bifidobacteria and lactobacilli. Good bacterial population in the colon has a range of positive effects on the body, such as supporting the immune system, killing harmful pathogens in the colon, producing vitamins and increasing calcium absorption. In addition, the by-product of bacterial fermentation is the production of short-chain fatty acids: butyrate, propionate and acetate that have been shown to have a number of beneficial properties for the body.

Since fructans are considered to be prebiotics, they are added to many processed foods to improve the quality of the product by increasing the fiber content. The most common fiber that is added to foods is inulin. Many people, who cannot tolerate FODMAPs, experience GI symptoms when they consume excessive amount of inulin. Checking the food label for the presence of inulin will help to prevent a flare up.

Note: You need to limit or avoid inulin only if it triggers your symptoms. If it doesn’t have an adverse effect on your body, this can be a good addition to your diet.

Fructan intolerance can be easily mistaken for gluten intolerance due to the presence of similar symptoms. Some people think that they are gluten intolerant because they experience bloating, flatulence and diarrhea from eating wheat products and avoid all foods that contain gluten.  In addition, gluten-free foods are marketed as healthier options, which is not true. You should be avoiding gluten if you have celiac disease or non-celiac gluten sensitivity which involves the immune response and can damage the intestinal lining.

Moreover, people who can’t tolerate fructans may be able to include small amounts with no problem. Tolerance level is individual and should be tested. You can see a Registered Dietitian to help you find your personal triggers and amount you are able to eat. There is no need to exclude wheat products if small or moderate amounts can be tolerated well. Monash University in Australia tests different foods at the lab for fructan presence and lists the amounts at which most people will or will not experience any adverse reactions.

For instance, some people may tolerate small or moderate amounts of fructans found in sourdough bread, 1 slice wheat bread or ½ cup spelt pasta, so there is no need to eliminate wheat products completely.

In summary, fructans are carbohydrates that may cause bloating, excessive gas, diarrhea, abdominal pain and/or constipation in some people with IBS and finding the amount that will not cause any GI distress will help to include a variety of foods in the diet.

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