By Hélène Baribeau, Nutritionist and Éric Simard, Ph. D., researcher in the field of aging.


Do you know the symptoms that characterize irritable bowel syndrome (IBS)? Abdominal pain, bloating, gas, alternating loose stools and diarrhea: these are some of the symptoms. This syndrome greatly reduces the quality of life. It is the second leading cause of absenteeism from work and school. Its prevalence in Europe and North America is around 10 to 15% of the population …

Changing the fiber intake in the diets of people with irritable bowel syndrome has been a staple in managing the problem for several years. However, the results of studies on increasing or decreasing fiber content are contradictory, as the evidence is weak regarding the impact of total fiber in this syndrome. On the other hand, it seems that soluble fiber, such as those found in oats, psyllium, as well as in many fruits and vegetables, may contribute to some reduction of symptoms.

In recent years, another approach seems to be more effective. It’s the FODMAP diet, developed by Australian nutritionist Sue Shepherd, to fight irritable bowel syndrome. This diet is gaining more and more attention thanks to the positive and significant results obtained through intervention studies. It would provide relief from IBS in about 75% of cases according to Sue Shepherd.

1- What does the acronym FODMAP stand for?

F = Fermentable (quickly fermented by bacteria in the colon)

O = Oligosaccharides (fructans and Galacto-oligosaccharides or GOS)

D = Disaccharides (lactose)

M = Monosaccharides (excess fructose of glucose)

A = And (and)

P = Polyols (sorbitol, mannitol, xylitol and maltitol)

The FODMAP diet would reduce symptoms by limiting foods containing carbohydrates (= sugars) which are poorly absorbed in the small intestine and poured in large quantities into the colon. Once in the large intestine, these sugars in some foods are fermented by bacteria, causing symptoms of bloating, gas, and abdominal pain. The FODMAP diet also limits the absorption of small carbohydrate molecules with osmotic capacity that increase water load in the colon, resulting in symptoms of loose stools and diarrhea.

2- What are the most concentrated sources of FODMAP that should be limited*?

  • Wheat (refined or whole), rye, barley, onion, garlic, artichoke, cashew nuts, pistachios → presence of fructans.
  • Legumes (lentils, peas, beans) → presence of GOS (galacto-oligo-saccharides).
  • Milk and yogurt → presence of lactose.
  • Apple, pear, watermelon, mango, honey, asparagus → presence of excess fructose in glucose.
  • Mushrooms, cauliflower, blackberries, mint and sugar-free chewing gum → presence of polyols.

* Non-exhaustive list

3- How to follow the FODMAP diet?

It is essential to get a nutritional assessment and be monitored by a nutritionist to apply this diet, as this approach has many restrictions and you have to know how to replace the foods that should be limited.

For example:

  • Wheat can be replaced by oats, rice, quinoa and buckwheat and gluten-free products made from rice, potatoes or tapioca.
  • Regular milk can be sourced from lactose-free milk or alternative milks such as almond, rice and oat.

Also, after following this diet for 2 to 8 weeks, it is important to carry out food tolerance tests to know which foods cause the most issues, in order to obtain an adapted eating plan. depending on the level of individual tolerance.

4- Is it for everyone?

Although reducing foods that are sources of FODMAP may improve the condition of people with IBS, that does not mean that FODMAPs should be eliminated from the diet of people who do not have a bowel disorder. FODMAPs, if well tolerated by the body, should be encouraged, as they are important for healthy gut flora.

5- The researcher’s opinion

This is a fascinating subject because it is very important to many people and because science is changing rapidly. I’ve witnessed this, since part of my PhD focused on digestive health on the use of a new species of probiotic. Let’s go back a bit to situate the science of today within this area.

Thirty years ago, we were convinced that antibiotics had no impact on the gut microbiota because when medication was stopped, the proportions of different bacteria returned to normal. This is what we believed. This is what was observed. The earth was flat.

Unfortunately, that was not the reality. This observation was due to the fact that we were unable to see changes in the proportions of the majority of the species present, and that we based the observations on the presence of the large groups of bacteria and yeast. It was subsequently possible, about ten years ago, to observe that certain species disappeared completely after the use of antibiotics. It was even possible to make a link between the use of antibiotics in children and an increased risk of developing irritable bowel syndrome for several years after treatment. Analytical methods now make it possible to closely follow minute variations in the composition of the microbiota in order to better understand their implications for human health.

Balance is in order

We now know that the balance of the gut microbiota is very important for a vast array of health problems and above all, digestive problems. For example, a reduction in bacteria from the Bacteroidetes and Firmicutes group, as opposed to an increase in Proteobacteria and Actinobacteria, has been shown to be a key factor linked to the development of inflammatory bowel disease (IBD). These are large groups of bacteria. Fine composition analysis is very complex.

This balance influences and depends on our immune system. Some people will thus have an imbalanced immune system because their microbiota is imbalanced, or even have imbalanced microbiota because their immune system is imbalanced. Both are possible and it depends on a number of factors including genetics and some external causes such as smoking, history of antibiotic use, and diet.

Food modulates the composition of the microbiota on a daily basis. Everything we eat each day creates variations in composition between the different species of bacteria that make up our gut microbiota. This is why the FODMAP diet can work well for IBS, but also for gluten intolerance or celiac disease. However, for the majority of people, these fermentable sugars are prebiotics; food for our good bacteria beneficial to health.

Each person is unique

Since this balance between good and bad bacteria depends on our genetics, with what we eat and our lifestyle, each person will react differently to the effects of food on its composition. Recall that there are approximately 100,000,000,000,000 bacteria in the intestine and that is approximately 10 times the number of cells in the human body and 150 times the number of genes in our cells. A recent study even showed that there are almost 2,000 new species of bacteria in our microbiota. Until recently, we considered the microbiota to be made up of 400 to 500 species of bacteria.

In this context of diversity, the FODMAP diet aims to restrict the set of molecules that can be problematic because they could promote the growth of bacteria causing inflammation. It’s not all molecules, and not all people, that will be problematic. It is therefore recommended to be accompanied by a nutritionist and to try to gradually reintegrate FODMAPs in order to find the ones that suit you. This should be applied over a long period of time in order to allow a new balance to occur in the microbiota for each of the foods considered. For this reason, periods of 2 to 8 weeks are usually recommended.

Some other foods should also be considered, such as meat consumption or food additives. Especially for preservatives, these are molecules that can kill certain groups of bacteria in our microbiota (good and less good) and modify our balances. It is therefore preferable to avoid them as much as possible.

What about supplements?

Besides FODMAPs, omega-3/omega-6 balance is also a very important facet within the diet. Omega-3s are used to produce anti-inflammatory molecules and omega-6s are used to produce pro-inflammatory molecules. Thus, when a person consumes too much omega-6 (especially animal fats and certain vegetable oils) at the expense of omega-3s (fatty fish and certain vegetable oils), they will have a tendency to develop more inflammation more easily. It’s best to eat fish more often but taking an omega-3 supplement can be a good way to make sure you get enough.

Taking probiotics can certainly help restore certain balances. It seems that some products would be more effective for some people. It may therefore be relevant to try different products to find the one that suits you best. The frequency of use needed will also depend on the person and their needs.

The next group of supplements to consider for gut inflammation issues are the polyphenols group. Be careful here, polyphenols are a group of more than 10,000 different molecules, mostly of plant origin. It is therefore a very generic term. First and foremost, make sure you’re getting enough fruits and vegetables for a good dose and variety. We consume between 900 mg and 1 g on average of plant polyphenols per day. It seems that the most studied polyphenol for intestinal inflammation is quercetin. Several fruits and vegetables contain it (and note that many of them contain high amounts of FODMAP).

However, the reported doses of these polyphenols in the scientific literature are very high and difficult to achieve even with supplements. Other polyphenols that may be of interest for intestinal inflammation are curcumin and resveratrol. The doses used in the published studies are also at high doses and remember that the quality of products on the market is very variable, especially for plant extracts.

We hope you will find this information useful, and we will be more than happy to answer your questions.



References :

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  • Varjú P, Farkas N, Hegyi P, Garami A, Szabó I, Illés A, Solymár M, Vincze Á, Balaskó M, Pár G, Bajor J, Szűcs Á, Huszár O, Pécsi D, Czimmer. Low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet improves symptoms in adults suffering from irritable bowel syndrome (IBS) compared to standard IBS diet: A meta-analysis of clinical studies. PLoS One. 2017 Aug 14;12(8):e0182942.
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