FODMAP and Irritable Bowel Syndrome – is “healthy food” really healthy for everyone?

My food diary – 19th of January 2019
Two slices of rye bread + avocado spread
An apple + tea sweetened with honey
Salad with pulses, edamame and beetroot
Yoghurt with blackberries and almonds
Cauliflower pizza crust topped with mushrooms and fresh onions

This looks like a perfect food diary we could easily find in a magazine, blog or website dealing with healthy lifestyle – surrounded with trendy words such as high-protein content, wholegrain, good fats, healthy sugar or powerfood.

What do all these foods and food ingredients have in common?

One obvious answer is: “they are healthy!”

True, in a way.


All these foods also share a very important feature in common: they are high in FODMAPs.

FODMAPs? What is that? Is that a new trendy term in the world of health and lifestyle?

FODMAP is the abbreviation for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. Instagram – you know, the best source of information when I want to check how popular a trend is – informed me that it must be a rather new term for most of you, with only 200’000 hits for #fodmap.

But not for me.

I have been suffering from gastrointestinal issues for many years. Many. M-A-N-Y. For actually so long that I even did not recall how everything started. I do recall all the medical investigations I went through, all the tests I have done and I am still doing on a regular basis to check the evolution, all the weird and sometimes irrelevant diagnoses I received, all the medicine I swallowed – hoping to have the symptoms under control, all the trials I did with food to try to help my condition.

One day, around 7-8 years ago, I have been labelled with the diagnosis Irritable Bowel Syndrome (IBS). I recall I did not react very well to this diagnosis, having the feeling everyone suffering from unexplained gastrointestinal issues would be thrown in this catchall category. To be honest, I am still having the same feeling, but at least I have digested (haha) the fact that I will have to live with that for the rest of my life. Even if no real treatment exists – except trying to lower the impact of the symptoms to live as normally as possible.

Great that you share your intestines’ intimacy with your audience, but maybe you should start by explaining what this Irritable Bowel Syndrome is.

As highlighted in its name, IBS is a syndrome, meaning a condition characterized by a set of associated symptoms. It affects the large intestine (also called colon) with symptoms including cramping, abdominal pain, bloating, gas, as well as diarrhea and/or constipation. Yes, very elegant and very poetic. It is a complex chronic condition with up’s and down’s, which can lead to psychological disorders including depression and anxiety – for up to 40% of patients [1]. Another characteristic of IBS is the so-called visceral hypersensitivity, i.e., the fact that patients experience abdominal pain within the inner organs at a more intense level in response to pressure, stimulation or distension within the abdomen.

On the contrary of Inflammatory Bowel Diseases (IBD, which include Crohn’s disease and ulcerative colitis), IBS will not lead to fatal complications, but people with moderate to severe IBS all report a poor quality of life – something I can only confirm. The constant fight against all the possible triggers, the difficulty in having a normal social life, the strict discipline it involves, the sleepless nights because of this dull pain, the overall exhaustion because of all these symptoms, the fact no one really understands, and the breathtaking abdominal pain or severe diarrhea that suddenly occurs despite all the precautions – it is not fun (understatement).

Indeed, that doesn’t sound fun at all. But what is then the link between IBS and FODMAP, since we have been discussing both of them so far?

In this great and sometimes exhausting journey called “how to survive with IBS and lower its impact on my life”, I have discovered that the major trigger, in my case, is food.

A special category of food.


In the beginning of this journey, I had always suspected that food was playing an essential role but I could not find exactly what was in common between all “dangerous” food ingredients. I made a big step on the day I went to the hospital to take a hydrogen breath test to examine my tolerance to both lactose and fructose. I was diagnosed intolerant to both. Fructose and lactose are both disaccharides – yes, exactly, the “D” letter in the FODMAP term. I therefore started to investigate much deeper this path. Today, I can officially announce that the only approach that helps me to lower the impact of IBS on my life is…. *drum roll*… A low FODMAP diet.

But let’s assume that I don’t belong to the 10-15% of the population who suffers from IBS worldwide – why would I care about this topic?

For two very important reasons.

First, because a large majority (probably close to 70%) of population experiencing IBS symptoms have no clue about this condition, and even less clue about how to lower the symptoms and increase the overall quality of their life [2].

The second reason is the one I find the most important. You remember the food diary listed at the beginning of this post? Yes, the very healthy one. Give this to an IBS patient and they will end up few hours later in their bed, in fetal position, sobbing and wondering what they did wrong. Yes, most of the food present in this food diary are high in FODMAP, therefore at high risk of triggering symptoms in IBS patients. And maybe also in a somewhat sensitive population.

Healthy for the common knowledge does not mean healthy for everyone. Apples, onions, honey, avocado, pulses, almonds, or cauliflowers have taken center stage in many lifestyle-related articles due to their potential health benefits. They might be healthy – but they are extremely risky for IBS patients.

Okay, you raised my interest. What are these FODMAPs, then?

FODMAPs are short-chain carbohydrates, in other words relatively small sugars, which have the three following characteristics [3-5]:

  • They are poorly absorbed in the small intestine during the digestion, so they basically continue their journey until they reach the large intestine;
  • They are rapidly fermented by the bacteria present in the intestine, leading to formation of gas; and
  • They are osmotically active, meaning they attract and hold water in the intestine, accelerating the intestinal transit.

***Isn’t it now time for the chemical intermezzo we all love?***

The family of carbohydrates, a macro-nutrient always listed in the nutrition facts of everything your buy at the supermarket, includes the following sugars:

  • Monosaccharides, such as glucose, fructose, and galactose. Monosaccharides are the simplest form of sugar we can find, the simplest sugar “unit”.
  • Disaccharides, such as lactose or sucrose. Disaccharides are formed with two monosaccharides bond together. Lactose is formed with one glucose and one galactose, while sucrose – the sugar you put in your coffee, also called saccharose – is formed with one glucose and one fructose. Lactase is the name of the enzyme that breaks down the lactose into glucose and galactose.
  • Polyols, such as sorbitol, xylitol, mannitol, maltitol, and isomalt. Polyols are sugar alcohols, meaning that their chemical composition also contain the so-called hydroxy function (-OH, which put them into the chemical category alcohols). Polyols are used in food industry as thickeners and sweeteners (especially in sweets and chewing gums) and in the pharmaceutical industry as excipients.
  • Oligosaccharides, which are carbohydrates formed with 3 to 10 units of monosaccharides and are mostly found in plants. Fructooligosaccharides (FOS), also called oligosaccharide fructans, are oligosaccharides with at least one unit of fructose. Similarly, galactooligosaccharides (GOS), are oligosaccharides containing at least one unit of galactose.
  • Polysaccharides, which are carbohydrates with more than 10 units of monosaccharides. Examples includes glycogen or starch, as well as cellulose. Polysaccharides made up of fructose molecules are called fructans.

Among all these sugars, I would rank fructose and fructans as the ones currently being subject to the researcher’s scrutiny due to the possible side effects on our health – especially in sensitive populations. But let’s first close this chemical intermezzo before getting a headache.

Awesome, now we all know what these compounds are. But how was it discovered that these carbohydrates could be linked to gastrointestinal symptoms?

The low FODMAP diet is actually a relatively new concept, since the term FODMAP has been for the first time coined only a decade ago. It had been known for a long time that some food, and especially some specific carbohydrates-containing food, could lead to gastrointestinal issues. However, it is in 2004 only that a group from the Monash University in Melbourne, Australia, introduced the acronym FODMAP and started to demonstrate with rather solid and well-conducted studies that IBS symptoms could be significantly decreased in IBS patients with reduction of FODMAPs intake [6].

Today, the Monash group remain the leading expert in this research. They are not only trying to better understand the mechanisms underlying the role of FODMAPs in IBS and other gastrointestinal conditions, but they also provide experimental data on the FODMAPs composition of a large diversity of food (i.e., they really measure this composition experimentally), which is extremely helpful for IBS patients.

Now that you mention that, so what is the role of FODMAPs in IBS pathology? How can such compounds lead to these symptoms?

These sugars are very nasty, because they have several effects in our bowel that can lead to annoying symptoms, most notably the following [7]:

  • Their presence in the intestine increase the amount of intestinal water, which can lead to pain due to intestinal distension (especially in patients with visceral hypersensitivity) and/or diarrhea.
  • Due to the fact they are poorly absorbed during their journey until they reach the large intestine, they will be fermented there by bacteria, which leads to the formation of two gasses: hydrogen and methane. This results in bloating and flatulence.

Flatulence? What is that?

An elegant word to say farts. Very interesting to see the diversity of words that can be used to refer to farts. I personally like flatus. Or wind, to be semi-elegant.

Abdominal pain, flatulence, bloating, gas, diarrhea… That doesn’t sound nice. What are the food that are high in FODMAPs, then?

An easy answer to this question would be a lot, followed by a list of foods that are at high risk to trigger symptoms in IBS patients. But it is unfortunately not so easy, since the FODMAPs content is also influenced by multiple other factors.

But let’s start with a small overview showing some basic trends, with first a selection of foods that are low in FODMAPS:

… And now a similar table, showing this time the foods high in FODMAPS:


This is only the starting point. Indeed, if you start to dig deeper into the low FODMAP diet, you will realize that:

  • For many food, the symptoms are dependent on the quantity eaten. For instance, having some roasted pumpkin pieces (less than 30g) in your salad will not be an issue. A pumpkin soup, however, can lead to serious pain because a soup basically concentrate all these carbohydrates during the process.
  • The amount of FODMAP in a dish is dependent on how the dish is prepared. Garlic and onions are both absolutely no go’s. These two are very nasty because they are typically added at the beginning of the preparation, so the FODMAPS (mostly fructans) will have plenty of time to be dissolved in the dish and be therefore “spread” everywhere. The only way to add a garlic flavor to a dish is to first sauté the garlic clove in oil during few minutes before removing the clove. FODMAPs being soluble in water but not in oil, they will not be present in the dish – but the flavors will.
  • Food from the same category do not always follow the same trend. Nuts are a good example: walnuts are okay (except if you eat more than 135 g in one go, which is pretty uncommon), macadamia nuts and peanuts as well. Almonds are okay only if you limit your consumption to ca. 10 nuts – same for hazelnuts. Cashew and pistachio nuts are not recommended – whatever the quantity ingested. All nuts indeed have a significant amount of GOS and fructans, but the amount depends on the variety of nuts. Now you can understand why I am always sorting out nuts during receptions or parties – not because I am not adapted to life (well…)
  • FODMAPs also depend on the part of the plant that is eaten, and its Two examples: bananas can be consumed when unripe (limited to one medium banana) but become high in fructans during the ripening process. One serve (75g) of broccoli heads is totally okay, but broccoli stalks contain a higher amount of fructose and should be therefore avoided.

 Oh, this sounds really complicated! What should I then do if I suffer from IBS and want to investigate this direction?

It is complicated, and that is why it is very important to (i) look for accurate and trustworthy information, and (ii) get professional support (GP, gastroenterologist, nutritionist, dietician, etc.) during your investigations.

Despite being less popular than other food-related topics, FODMAPS have gained more attention in the last couple of years, meaning that the amount of information that can be found online is also now substantial – but sometimes inaccurate. The most adequate information I fully recommend comes from the Monash University, especially:

  • The Monash University FODMAP Diet app, available for both iOS and Android and downloadable here, that contains clear recommendations about the foods that should be eaten or avoided. You’ll have to pay for the app ($12.99 AUS) but it is clearly, CLEARLY worth it. They don’t exaggerate when they say that it is a life-changer app – and the money you pay is anyway used for further research on this topic.
  • The Monash FODMAP blog, where research on FODMAP and IBS is shared with the readers, using easy words and always followed by clear recommendations.

But does this mean that I should remove all FODMAPs from my diet for the rest of my life? That I am not allowed to eat honey, mango and asparagus anymore?

No. The first important message is that we are discussing a low FODMAP diet – which is not the same than a no FODMAP diet.

Secondly, since IBS-related symptoms and FODMAP sensitivity is also very much individual, the implementation of a low FODMAP diet should follow these three phases [1,5]:

  • Elimination phase – a strict low FODMAP diet lasting 2-4 weeks to see which improvements can be observed in IBS symptoms;
  • Reintroduction phase – lasting 6-8 weeks, where FODMAP-containing foods are systematically reintroduced and symptoms recorded, to identify the individual sensitivity to FODMAPs and determine intolerances and tolerances;
  • Personalization phase – application of the personalized version of low FODMAP diet.

It is therefore important to remember that the elimination phase is not meant to be a long-term solution, but a first essential step before reintroducing FODMAPs individually.

But since IBS symptoms are improved in many IBS patients during the elimination phase, as supported by studies, why not just sticking to this diet during the entire life?

Obvious reasons are that it is difficult to follow such restrictive diet more than few weeks and that it can lead to vitamins, dietary fiber and micronutrients deficiency.

More importantly, FODMAPs do have positive physiological effects, including stimulation of beneficial microbes in the gut microflora and reduction of cholesterol levels in blood [1,4,5]. The gut microbiome (all the microorganisms living in our gastrointestinal tract, including roughly trillions of bacteria – yes, trillions) is currently one of the very hot topics in today’s research due to the potential role it might play in multiple diseases, but it remains unclear what effects modifications of the microbiome composition may have on our health.

Similarly, we do not have sufficient data yet to evaluate the efficacy and safety of a low FODMAP diet on a long-term basis, i.e., more than 18 months. Sticking to a strict elimination of all FODMAPs during many months is therefore not recommended. The long-term effect of a low FODMAP diet is for sure the field of research where efforts will be put in the coming years.

And in the meantime?

That flatus (plural: flatuses) becomes the Word of the Year 2019.

That restaurants stop topping their salads with microscopic pieces of fresh onions.

That this post creates a wake-up call in those who have adopted a healthy lifestyle, but who have just not felt okay since that time.

Don’t forget that something labelled as good or healthy by your friend, your neighbor, this famous Insta-influencer, this health-guru podcast-host or your personal trainer and fitness hero does not mean that it is also healthy for you.

Stay tuned… And critical!

Dr. Iza

tl; dr

  • The acronym FODMAP refers to Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.
  • FODMAP are poorly absorbed in the intestine, rapidly fermented and osmotically active, leading to bloating, cramps, pain, gas, constipation or diarrhea in sensitive population, particularly in patients suffering from irritable bowel syndrome (IBS).
  • FODMAPs are present in a lot of foods that are often labelled as healthy, such as avocado, onions, honey, pulses, many vegetables and fruits, some nuts, etc. The amount and impact of FODMAPs is also influenced by the quantity eaten, the way a dish is prepared, the ripening and part of the plant used.
  • If you want to follow this diet or get more information on the content of FODMAP of specific food, refer to official guidelines and source of information, such as the Monash app/blog.
  • Is this diet better than other approaches in IBS? A majority of IBS patients indeed report a better quality of life with a low FODMAP diet, with decreased symptoms.
  • The long term effects of a low FODMAP diet (longer than 18 months) remains poorly studied yet, especially on the microbiome composition and the impact on the organism (beyond the gastrointestinal tract).
  • A low FODMAP diet is not the same than a no FODMAP diet.
  • Food labeled as healthy or superfood might indeed bring some benefits in a healthy population, but it might trigger many discomfort and severe symptoms in a relatively large part of the population, which probably ignore this.
  • If you experience unusual pain, bloating, discomfort, diarrhea or any other gastrointestinal symptoms after having eaten “healthy food”, discuss it with your GP.


  1. Mitchell, J. Porter, P.R. Gibson, J. Barret, M. Garg, Review article: implementation of a diet low in FODMAPs for patients with irritable bowel syndrome – directions for future research. Aliment Pharmacol Ther 49 (2019) 124.
  2. Canavan, J. West, T. Card, The epidemiology of irritable bowel syndrome. Clin Epidemiol 6 (2014) 71.
  3. Vakil, Dietary fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) and gastrointestinal disease. Nutr Clin Pract 33 (2018) 468.
  4. Catassi, E. Lionetti, S. Gatti, C. Catassi, The low FODMAP diet: many questions marks for a catchy acronym. Nutrients 9 (2017) E292.
  5. Eswaran, J.P. Farida, J. Green, J.D. Miller, W.D. Chey, Nutrition in the management of gastrointestinal diseases and disorders: the evidence for the low FODMAP diet. Curr Opin Pharmacol 37 (2017) 151.
  6. R. Gibson, History of the low FODMAP diet. J Gastroenterol Hepatol 32 (2017) 1:5-7.
  7. M. Staudacher, K. Whelan, The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS. Gut 66 (2017) 1517.

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