Fructans & the Low FODMAP Diet

 Fructans & the Low FODMAP Diet

Garlic and onion on wooden background‘ by Antonova Anna licensed as Standard Image. Foods shown in photo contain high levels of fructans.

Fructans & the Low FODMAP Diet

Understanding what fructans are and how they fit with the low FODMAP diet can be tricky. Fructans like to lurk in a variety of foods, from fruit and veggies right through to cereal grains. They are also added to processed foods. This article is going to explain what they are and how to avoid them.

What are fructans and why are they a problem?

Fructans are oligosaccharides and polysaccharides that store carbohydrates in a variety of vegetables, for example, onions, garlic and artichokes, fruits such as bananas, and in cereals (Gibson & Shepherd, 2009; Muir et al., 2007; Monash University App, 2017). Unripe common bananas contain low levels of fructans and are safe to eat, however as the bananas ripen the fructan levels increase to a high FODMAP level. In the FODMAP acronym fructans belong under the ‘O’ for oligosaccharides. Humans lack the enzyme needed to break down the fructose molecule chains that fructans are made of, which means they end up being malabsorbed in our small intestines (Gibson & Shepherd, 2009; Muir et al., 2007). The fructans are then fermented by the gut bacteria, which can cause gas, bloating, pain, reflux, and altered bowel movements (Muir et al., 2007; Monash University App, 2014; Scarlata, 2010).

There are two types of fructans:

  • Fructans with shorter chain lengths (2-9 units) are called fructo-oligosaccharides (Oligos-FOS for short)
  • Fructans with longer chain lengths (10 units or greater) are called inulin. Inulin has already been discussed in depth in a previous article – you can read more about inulin here.

(Muir et al., 2007)

For the purpose of this article, there will be no differentiation between the types of fructans. Additionally, the different types of fructans are not labeled separately in the Monash University Low FODMAP app (Monash University App, 2014).

Fructans consist of soluble fibre (Scarlata, 2010). Adding fructans to processed food is a growing trend in the food manufacturing industry. This is because fructans (especially inulin) are considered a functional ingredient that can increase fibre content of processed food (Scarlata, 2010). The fermentable fibre is meant to help the growth of ‘friendly’ gut bacteria because they act like prebiotics (Gibson & Shepherd, 2009; Scarlata, 2010), which is great for normal people but not so great for people who can’t tolerate FODMAPs! This means you should check the labels of processed foods and supplements for inulin, added fibre, and other fructans.

Where are fructans found?

Plants use fructans as storage carbohydrates. This means fructans can be found in a wide range of fruits, vegetables and cereals (Gibson & Shepherd, 2009). Most types of beans/pulses/legumes and some nuts are also high in fructan containing oligosaccharides (Monash University App, 2014). One of our major sources of fructans is wheat, which means cutting out wheat can dramatically decrease our fructan intake (Gibson & Shepherd, 2009; Scarlata, 2010). Below is a table of high FODMAP foods that contain fructans. This table is by no means intended to provide a full list of fructan-containing foods, but to show how many different foods contain fructans. For a more comprehensive list of fructan-containing foods and their FODMAP levels, please refer to the Monash University phone app or low FODMAP booklet.

High FODMAP Foods Containing Fructans (non-exhaustive list)

  Fruits  Vegetables  Cereals
Grapefruit Chicory root Rye
Nectarine Globe artichoke Pumpernickel bread
Persimmon Jerusalem artichoke Kamut
Plum Beetroot   (>2 slices) Wheat (dependent on serving size)  
Pomegranate (>38g) Savoy cabbage (>1/2 cup) Barley
Watermelon Garlic Spelt   (dependent on serving size)
Some types of dried fruit   Leek (bulb)  
 Common banana (ripe) Mange tout (> 5 pods)  
  Onion (white, shallots, Spanish)    
  Spring onion bulb  
  Snow peas (> 5 pods)  

(Source: Muir et al., 2009; Monash University App, 2017)

Do different foods have different fructan levels?

Different foods can contain different levels of fructans. It is also important to note that cooking, manufacturing or refining processes, and the fermentation of foods can change their FODMAP rating and fructan levels. For example, spelt sourdough bread is lower in FODMAP levels as the yeasts use the fructans during the fermentation process (Monash University, 2015). Another example of changes in fructan levels is the drying of fruit. The drying process concentrates the sugar present in the fruit and can increase the fructan levels, even if these fructan levels weren’t detectable in the fresh fruit (Monash University, 2015). The processing of cereal grains can also change the fructans levels in the end-products.  The tables below indicate how fructan levels can change between foods.

Table One: High FODMAP Vegetables Containing Fructans

  Vegetable  Grams of Fructans Per Average Serve*
 (serve size in brackets)  
  Grams of Fructans per 100g  
Beetroot   0.27 (68g)   0.40
White onion   0.28 (16g)   1.8
Spanish onion   0.30 (16g)   1.8
Leek whole   0.43 (83g)   0.5
Garlic  0.52 (3g)   17.4
Spring onion bulb   1.01 (16g)   6.3
Shallots  1.1 (12g)   8.9
Jerusalem  artichoke   6.1 (50g)   12.2

 (Source: Muir et al., 2009)

Table Two: Cereals Containing Fructans

  Cereal  Grams of Fructans per 100g  
Unprocessed Rye   4.2
Unprocessed Wheat     1.3 – 1.9
Unprocessed Spelt 1.1

(Source: Verspreet et al., 2015)

Reintroduction of Fructans

Section Updated on 21/04/2016

After the elimination phase of the diet, fructans can be re-challenged and reintroduced. Fructan levels can vary greatly between different fruits, vegetables, and cereal grains. This means you need to test one to two foods in each of the different fructan groups to find your tolerance levels (Martin, 2015). FODMAP reintroduction specialist, Lee Martin (RD), recommends that you re-challenge each fructan group separately:

Number of Re-challenges

Fructan Group

Examples

Choose Two

Fructan containing vegetables

Garlic, leek bulb, onion (red or white), spring onion bulb

Choose One

Fructan containing fruit

Dried dates, dried pineapple, raisins, grapefruit, persimmon

Choose Two

Fructan containing bread, cereals & grains

Barley flakes, rice krispies, spelt flakes, white wheat bread,  cous cous

(Table Information Sourced from: Martin, 2015)

For more information, you can find my overview of the reintroduction phase here. Otherwise for a complete guide on reintroducing FODMAPs, check out Lee Martin’s Complete Guide to Re-challenging and Reintroducing FODMAPs.

Testing different fructan containing foods means you are more likely to find a fructan level you can tolerate. Hopefully you will be able to add some fructan containing foods back into your diet depending on your tolerance levels.

Final Thoughts

Until you figure out your tolerance levels to fructans you need to avoid high fructan foods in the elimination phase of the diet. Also remember to check all processed foods for added fructans from high FODMAP food sources like inulin and chicory root. If you are lucky, you might be able to add some fructans back into your diet during the reintroduction phase.

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REFERENCES

1. Gibson P. & Shepherd S. Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach. Journal of Gastroenterology and Hepatology Journal of Gastroenterology and Hepatology. 2009: Volum 25: Issue 2. 252-258. Retrieved from:http://onlinelibrary.wiley.com/doi/10.1111/j.1440-1746.2009.06149.x/abstract. Retrieved on: 2015-05-25. (Archived by WebCite® at http://www.webcitation.org/6YnUvKR7O)

2. Muir J., Shepherd S., Rosella O., Rose R., Barrett J., & Gibson P. Fructan and Free Fructose Content of Common Australian Vegetables and Fruit. Journal of Agricultural and Food Chemistry. 2007: Volume 55: Issue 16. 6619-6627. Retrieved from:http://pubs.acs.org/doi/abs/10.1021/jf070623x. Retrieved on: 2015-05-25. (Archived by WebCite® at http://www.webcitation.org/6YnVSnpCi)

3. Monash University App. About Section & Food Guide. The Monash University Low FODMAP Diet App. 2014: Edition 4.  Retrieved from :http://www.med.monash.edu/cecs/gastro/fodmap/iphone-app.html. Retrieved on: 2015-05-25. (Archived by WebCite® at http://www.webcitation.org/6Wog73c8B)

4. Scarlata, K. The FODMAPs Approach — Minimize Consumption of Fermentable Carbs to Manage Functional Gut Disorder Symptoms. Today’s Dietitian. 2010: Volume 12: Issue 8. 30. Retrieved from:http://www.todaysdietitian.com/newarchives/072710p30.shtml. Retrieved on: 2015-05-25. (Archived by WebCite® at http://www.webcitation.org/6YnW8k8LB)

5. Monash University. Frequently Asked Low FODMAP Diet Questions. Monash University. 2015. Retrieved from:http://www.med.monash.edu/cecs/gastro/fodmap/low-fodmap.html#4. Retrieved on: 2015-05-25. (Archived by WebCite® at http://www.webcitation.org/6YnWbqvZc)

6. Verspreet J., Dornez E., Van den Ende W., Delcour J., Courtin C. Cereal grain fructans: Structure, variability and potential health effects. Trends in Food Science & Technology. 2015: Volume 43: Issue 1. 32-42. Retrieved from:http://www.sciencedirect.com/science/article/pii/S0924224415000266. Retireved on: 2015-05-25.

8. Martin, L. Re-Challenging & Reintroducing FODMAPs: A guide to the whole reintroduction phase of the low FODMAP diet. Lee Martin. 2015. Retrieved from:http://www.reintroducingfodmaps.com/welcome.html. Retrieved on: 2015-12-07. (Archived by WebCite® at http://www.webcitation.org/6dbukJJ4o)

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Comments

  • Lisa 26/05/2015 1:29am (2 years ago)

    excellent post Alana! Very informative and helpful :)

    • Alana Scott 26/05/2015 3:22am (2 years ago)

      Thanks Lisa!

  • Jen 21/08/2015 2:32am (2 years ago)

    Great article. Thanks Alana :)



    Can I ask why bananas seem to be mentioned above and in other resources as containing fructans but they don't usually appear on the list of fruit to avoid. I keep coming across it

    • Alana Scott 21/08/2015 4:14am (2 years ago)

      Hi Jen,
      Bananas do contain fructans but they are at a low level that is generally well tolerate, which is why they are on the safe list. Hope that helps :-)

  • lisa 27/09/2015 2:03am (2 years ago)

    Love this website for great recipes and informative articles - keep it up!

    • Alana Scott 27/09/2015 3:56am (2 years ago)

      Thank you for the lovely feedback Lisa!
      Alana x

  • Sarah 11/10/2015 7:53pm (2 years ago)

    Hiya :-)



    another really helpful post.



    Do you know if it is likely that a person may be able to tolerate some foods that are in the same group but not others or would a person react to- in this example- all foods that contain fructans?



    I am not eating any of the foods listed above at present but I recall that I used to have a problem with onions and garlic which caused me abdominal pain but don't recall ever having any problems with grapefruit or beetroot.

    I also found raw onions were less tolerated than cooked onions which caused less symptoms.





    I wondered what your thoughts/experiences are?

    • Alana Scott 11/10/2015 8:37pm (2 years ago)

      Hi Sarah,

      Different foods have different FODMAP levels so it is possible you will be able to tolerant some foods in a particular FODMAP group but not others. This means you can test different foods within a FODMAP group and see if you can tolerate them. For example beetroot contains low amounts of FODMAPs when compared to onion or garlic, which might be why you tolerate beetroot better.

      We also know that cooking foods can alter their FODMAP content, although it is hard to tell if cooking a food would reduce the FODMAPs enough for their ratings to change from high to low. This does explain why some people can tolerate cooked onion better than raw onion.

      I hope that helps!

  • Karli 08/01/2016 4:33am (22 months ago)

    Currently testing my levels for Fructan malabsorbtion and have had varied results.... Can I ask why if garlic has a high level of fructans than onion it is only Level B where as onion is Level C?

    Also I had a reaction to wholemeal bread but in 50% of my tests I have been okay with onion and sometimes garlic. I also tested rye bread and had mixed results....

    Thanks

    Karli

    • Alana Scott 08/01/2016 4:42am (22 months ago)

      Hi Karli,
      Okay so generally you would eat a much larger serve of onion than you would eat of garlic and this is why they are rated differently. If you are okay with the other fructans but consistently reacting to bread then it is possible you are reacting to something else in the bread. Hope that helps.
      Cheers,
      Alana

    • Suzi 03/02/2017 4:29am (9 months ago)

      Hey Karl, I am a bit like you, I think. I am only just starting to research this because of garlic and to a lesser degree, wheat bread. I am sick of being sick! Funny that I can eat fresh garlic but not processed and not wheat bread. Took me a long time to figure it out

  • Caitlin 24/02/2016 12:25am (20 months ago)

    This website has been so helpful to me through my FODMAP journey! Thank you for posting such valuable information.

    In line with some questions above, I have just finished testing the first Fructan group. It seems that I don't have a reaction to the wheat bread, but I do to the rice crispies. Does that mean it's specifically inulin that I need to avoid? I am having trouble understanding the difference between the two food items. Thank you!

    • Alana Scott 24/02/2016 8:47pm (20 months ago)

      Hi Caitlin,

      Both wheat and rice cripsies contain fructans. It is possible that your wheat bread is lower in fructans than your rice cripsies which is why you are only reacting to the rice cripsies. There are two different types of fructans: fructo-oligosaccharides and inulin. Unfortunately the Monash app does not distinguish between the two types of fructans. It is not clear which ones are in the wheat bread or rice cripsies. What I think is happening is that you tolerate cereal fructans at a certain level and if you stay under that you will be able to manage your symptoms. If you want to specifically test your response to inulin try testing with chicory root or globe and Jerusalem artichokes as these foods are known to be high in inulin. Let me know if you need more information.
      Cheers,
      Alana

      • Caitlin 01/03/2016 9:41pm (20 months ago)

        Thanks so much for the information! I'll give the Jerusalem artichokes a try and see what happens.

        • Alana Scott 03/03/2016 8:48pm (20 months ago)

          That's okay - have you tested fructose yet? I've just remember that Jerusalem artichokes also contain fructose which can give conflicting results when testing them if you are sensitive to fructose. Your other options are to try just testing globe artichokes (they only contain fructans), onion or garlic which also contain vegetable fructans (some of which is inulin). I hope that helps :-)

  • Katrina Moore 25/04/2016 6:13am (18 months ago)

    Hi Alana, could you please tell me if fejoias and nashis are ok on the fodmap diet.I cant find anything about either of them.Thanks Katrina

    • Alana Scott 25/04/2016 7:22pm (18 months ago)

      Hi Katrina,
      Do you have the Monash Low FODMAP app? If you don't I highly recommend you grab it as it contains the most up-to-date food lists for low and high FODMAP foods straight from Monash University who are the lead researchers of the low FODMAP diet.

      In terms of your question. Fejoias are high FODMAP for fructose. Nashi pears are high FODMAP for both fructose and polyols. This information is from the Monash low FODMAP app. I hope that helps!

  • Lanie sidney 25/04/2016 1:13pm (18 months ago)

    Hi there. My 5 year old is diary free from 6 months then following various elimination diets, diagnosed as fructose malabsorption. I've recently been handed FODMAP food supplier booklet by his dietician. This seems to contradict some of the info I've found on fructose malabsorption. Can you shed any light, dietician isn't very sure. Many thanks.

    • Alana Scott 25/04/2016 7:48pm (18 months ago)

      Hi Lanie,

      Could you tell me what booklet you have been given? That way I can figure out exactly where the differences are.

      Remember that the low FODMAP diet was originally designed for IBS before it was discovered that it works for many people with fructose malabsorption. The goal is the low FODMAP diet is to remove foods that contain excess fructose. This means some foods (like tomatoes) that have equal glucose to fructose ratios but high overall fructose levels. This means these foods should be well tolerated by most people (the glucose helps us absorb the fructose), however very sensitive fructose malabsorbers (and sometimes children) these foods might need to be tested then removed as needed.

      Does that answer your question?

  • Lee Savard 30/10/2016 7:18pm (12 months ago)

    I was diagnosed with severe Fructose Malabsorption and Lactose Intolerance in 2011. I had to do all my own research, since there was not much out there at the time. I was very hungry for quite a while and gradually was able to tolerate more foods, but others were out of the question. I did well most of the time, but now I am back in a bad "bout" due to eating too much of the things that I had built up a toleration for, and I seem to be starting from "scratch." I am trying to find recipes for bread without white flour, no wheat. Not sure if corn is safe since the FODMAP charts conflict. I have started drinking rice milk and I'm not sure if that is causing my severe constipation. I have a bunch of new "safe" flours, Amaranth, Oat flour, Teff, Rice flour, tapioca, but all the recipes I find for bread, have other things that I can't have and it's hard to substitute. I have been eating Rice Krispies, but not sure if that is o.k. Also, oatmeal every other a.m., but again the charts conflict. Any information out there for this extreme sufferer?

    • Alana Scott 30/10/2016 8:06pm (12 months ago)

      Hi Lee,

      I'm sorry to hear you are struggling. As your symptoms have gotten worse I would recommend you check in with your doctor just to check there isn't any thing else going on. Also if you haven't seen a dietitian yet I would ask for a referral.

      Going back onto the low FODMAP elimination plan might help ease some of your symptoms, but it may not ease your constipation completely. Often constipation needs multiple management strategies. You might find this article useful https://www.alittlebityummy.com/blog/12-tips-for-managing-constipation/

      Also for the most up-to-date low and high FODMAP food lists I would recommend you get the Monash low FODMAP app. This app has been developed by Monash University (they created the diet) and contains recommended portion sizes for each food, which is helpful as you try and get your symptoms under control. You can find out more about the app here: http://www.med.monash.edu.au/cecs/gastro/fodmap/iphone-app.html

      Please let me know if there is anything else I can help with.

      Cheers,
      Alana

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