FODMAP Elimination & Reintroduction

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Table of Contents
Probiotics Before Elimination Diet
The FODMAP Elimination & Reintroduction Diet
What Is A Normal Portion Size?
Reintroduction Importance And Tips
Prebiotics vs Low FODMAP Diet
Low FODMAP Prebiotics
Overcoming Low FODMAP Diet Challenges
Alternative Food Triggers
Further Reading And References

Probiotics Before Elimination Diet

If you are already eating as healthy a diet as you can, it is recommended to try a good probiotic which has scientific evidence for IBS prior to trying the FODMAP elimination and reintroduction diet, since the probiotic may make you more tolerant to some foods, which means that you may not need to eliminate certain foods unnecessarily. Equally, your symptoms might become much better controlled which means that you don’t need to try the FODMAP elimination and reintroduction diet at all. This is the best case scenario, since FODMAPs are good for your health, provide feed for your microbiome (are prebiotic) and you want to eat as many FODMAPs as you are able.

If you are not eating a healthy diet, purely out of habit (rather than food intolerances), it is best to try to improve your diet before anything else. You may find that this improves gut symptoms in the long term without needing to do anything further.

The FODMAP Elimination & Reintroduction Diet

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are types of carbohydrates found in some foods, that can cause symptoms in some IBS sufferers.

If a well studied probiotic has not reduced IBS symptoms sufficiently after a 3 month trial, you can use the FODMAP elimination and reintroduction diet to uncover any remaining food intolerances.

Please note that this is the only accurate method of finding out which foods that you are intolerant to. There are many ‘tests’ available to buy, but these have no scientific basis. By using these tests, you may only land on food intolerances by chance and you could end up eliminating foods unnecessarily due to their inaccuracy. (1)

It is worth reading the Diarrhoea & General Symptoms page which discusses gut microbes before reading this page if not done so already.

The FODMAP elimination and reintroduction diet is best conducted under the guidance of a dietitian via a GP referral.

If you download the Monash University FODMAP app, the app will tell you which foods contain FODMAPs and in what quantities. Registered Dieticians will also be able to provide you with the required booklets to help you follow the diet since some elements of it can be quite complex (2) (20).

In general and as a guideline:

eliminate all FODMAPs for 2 weeks
reintroduce one food from each FODMAP group at a time starting in small quantities, increasing over a 3 day period and wait up to 4 days for symptoms. The rules are a bit more complex than this since the booklets suggest some FODMAP foods, such as garlic, behave slightly differently to other foods in the same FODMAP group and need to be tested in addition to other FODMAPs in the same group. There is no need to test any other FODMAPs from the same group apart from the exceptions mentioned in the booklet.
from personal experience I have found it useful to go much slower than this – only introducing a small amount (1/4 to 1/3 of a normal portion size) of the same food for 3 days
during the testing period, keep a food diary with a daily symptom tracker. Record the date, what you have eaten and what symptoms you are experiencing that day. There are apps available for this, but I found keeping a simple spreadsheet was enough. I would include any new foods I am testing in bold, so that these stand out
increase the amount of food if tolerated or no symptoms or cut back to the previous amount if you have symptoms for longer and then try to increment again. Theoretically, your microbiome can adapt to handling a new food if introduced very slowly and your bad bugs are under control with a good probiotic. The idea is to find the quantity of that food that you can tolerate rather than eliminating the food altogether. Although you may find with some foods, they give symptoms no matter the quantity. As mentioned, ideally you want to eat as many FODMAPs as you can since they are good for your health
from experience I found that my transit time (eating food to waste elimination) is around 48 hours. When I had emptied from either diarrhoea or colonoscopy preparation, it was usually 48 hours before I experienced a bowel movement again. This also correlated with my food reintroductions. When I introduced something new, I would often experience symptoms not the next day, but the day after that. However, everyone will be different in this regard
if you do experience symptoms during the test of a specific food and you have completed that test, wait for the symptoms to subside before starting the next food test
if it became clear after some time, that I couldn’t tolerate a food even in small quantities, I would make a note of this in a different column and colour that food in red text. Conversely if a food was OK I would put that food in the same column in green text. It is important to do this, since as time goes on it is really easy to lose track of what you have tested and what the outcome was and you don’t want to get caught in an endless loop of having to retest foods unnecessarily
it is important to note that it is a good idea to periodically re-test some foods after a while of eliminating that food, in case that particular food intolerance has settled. For example, stressors may have reduced, you may have included stress reduction practices into your routine such as exercise and meditation or your microbiome diversity has improved – there can be a variety of factors that increase tolerance to a specific food. Plus staying away from a food for a while may help gut reactivity towards it. Equally a specific intolerance may remain after re-testing. All of this is under research and the science behind food intolerances needs expanding

Many people with IBS don’t have diverse gut bacteria – it has been found that people who lack a diverse microbiome are more prone to diseases in general. In the long run, if you can get your symptoms under control, the ideal situation is to have a very varied diet – lots of different coloured fruits and vegetables, a variety of protein and carbohydrate sources including cereal fibres. This encourages different types of bacteria to increase in numbers in the gut in order to handle these different foods resulting in bacterial diversity. The fact that you may not be able to consume a whole portion of a specific food may not be such a bad thing, since this means that you can make up that portion with another food which you can only eat in small amounts, which helps to improve the diversity of bacteria in your gut overall. This may seem a long way off, but with the right treatment all of this is possible. At my worst, most foods, even low FODMAP ones triggered symptoms and at other times all I could consume to control my IBS was white rice, protein and very limited low FODMAP vegetables. Using the approach above (particularly introducing Alflorex) I am now able to consume far more foods including lots of cereal fibres and wholewheat bread which was unheard of for me, though some food intolerances still remain.

What Is A Normal Portion Size?

If you are going to start testing foods with a 1/4 or 1/3 of a normal portion size, you may ask what is a normal portion size? There are some useful links here, here and here to help guide you. IBS symptoms from a specific food can be very quantity dependent. You may find there are some foods that you can only eat in small amounts, but to aid diversity in the diet, it may still be worthwhile consuming these in the amounts that you can tolerate. Some people may simply be overconsuming certain foods i.e. consuming more than a normal portion size and experience trouble. In these instances it might just be a case of checking the quantity of the food against the standard serving size. Sometimes reducing to a normal serving size resolves the issue.

Another thing to be aware of is the concept of FODMAP stacking, whereby multiple ‘green’ servings of FODMAPs are consumed in one meal. Monash University advises that their ‘green’ servings are quite conservative and should allow for more than one FODMAP containing food as might be found in a meal. However, for those experiencing problems, this is something to bear in mind. There is guidance on this here and here.

Reintroduction Importance And Tips

This topic and tips on reintroducing FODMAPs are discussed in-depth in these articles (3) (4) (5).

Foods containing Fructan and GOS (galacto-oligosaccharides) FODMAPs act as feed for your good gut bacteria, helping them to grow and increase in number. The good bugs help to control the bad bugs, which can cause IBS symptoms. Canned legumes such as chickpeas or 4 bean mix contain small amounts of GOS, which shouldn’t cause significant symptoms, but enough to gradually help the good bacteria to grow. Much of the GOS leaches into the water in the can, so rinse the canned pulses thoroughly, which leaves a small amount of GOS behind. (21) (7)

Note that the FODMAPs that you react to can change over months or years, depending on your symptoms. You may find that you are able to reintroduce more FODMAPs in time. It is important to slowly reintroduce some higher FODMAP foods and, as discussed above, re-test your tolerance occasionally and in varying amounts. (3) (6) The key is to customise your diet so that you are eating as wide a variety of foods as possible, in quantities that you can tolerate, whilst also controlling symptoms. Moderate amounts of Fructans and GOS are often better tolerated. (6)

For the fibre-sensitive it is best to make any increases in fibre very slowly, particularly in regard to cruciferous vegetables such as: cabbage, broccoli, and cauliflower. In studies, those who are fibre sensitive can tolerate fibre more effectively after consuming 1-2 tablespoon of fibre rich foods daily for two weeks. (8)

The gut microbiome and digestive enzymes secreted are crafted by the foods that we eat regularly. If possible, it is best to rotate your diet every few weeks to increase diversity of your gut bacteria and enzymes. In practice, this could mean only eating foods that you have reintroduced just once or twice a week rather than every day. (9)

If you need FODMAP friendly sweeteners, there is an article on this here (10).

Prebiotics vs Low FODMAP Diet

In a study, IBS patients were either put in a low FODMAP group (given a low FODMAP diet plus a placebo supplement) or a prebiotic group (given the prebiotic supplement, galacto-oligosaccharides plus a Mediterranean-type diet).

For 4 weeks during the diet/supplementation period, gut microbiota composition and gas production were monitored and for 2 weeks after discontinuation. (11) (12)

Those on the low FODMAP diet experienced improved IBS symptoms (such as pain, distension, bloating, and flatulence), but decreased Bifidobacteria, presumably due to reduction in prebiotic fructan and GOS intake. (11) (12) (13) This was in line with previous studies. Two weeks after discontinuation of the low FODMAP diet Bifidobacteria increased, showing that this effect was temporary. (11) (12) Bifidobacteria perform an important role in digestion and keeping harmful bacteria at bay (14). In fact, Bifidobacteria probiotic supplementation reduces IBS symptoms (13). Additionally, those on the low FODMAP diet showed increases in Bilophila wadsworthia, a bacterium implicated in excess gas and intestinal inflammation, which persisted for two weeks following discontinuation of the diet. This matched with an increase in bloating over this period. (11) (12)

A combination treatment of low FODMAP diet and Bifidobacteria probiotic supplementation has never been explored, but may guard against the negative effects of the low FODMAP diet on the gut microbiome. (13)

Those in the prebiotic group also experienced reduction in pain, distension, and bloating by the end of week 4. However, Bifidobacterium increased and Bilophila wadsworthia decreased; both changes persisted after 2 weeks of discontinuation of the prebiotic. Symptom improvement was maintained in the 2 weeks following prebiotic supplementation; however, this improvement was not maintained by the low FODMAP group in the 2 weeks following discontinuation of the low FODMAP diet. (11) (12)

At first, the prebiotic group experienced an increase in flatulence, which resolved as the gut microbiota got used to the prebiotic. Flatulence returned to the levels normally felt by the IBS patients 7-10 days after adjusting to the supplement, but had not improved as it had with the low FODMAP diet. (11) (12)

Symptom improvement from prebiotic fibres would have been related to changes in the gut microbiota. Further research is needed to understand how long symptom improvement lasts with prebiotic supplementation, helping to guide the best use of prebiotics in the management of IBS. (11) (12)

A low FODMAP diet reduces feed for the microbiome, due to a decrease in the availability of fermentable carbohydrates leading to a reduction in beneficial Bifidobacterium, Faecalibacterium prausnitzii and Clostridium Cluster IV levels. Therefore FODMAP restriction should only take place in the short term, followed by reintroduction and personalisation, preferably with the support of registered dietitian. (19) For these reasons IBS sufferers should try to eat as many FODMAPs as are tolerated.

Restrictive diets are not necessarily the panacea for digestive issues. Emerging data
indicates that that microbiome adapts to the consumption of dietary fibres using fermentative pathways that lower gas production. (15)

The above study mentions the potential positive effect of taking prebiotics on IBS. It is unclear whether the study takes into account individual reasons for someone’s IBS. For instance if they have some dominant bad bugs. Potentially, in these cases, the bad bacteria would be fed by the prebiotics, making the situation worse. Intuitively, it would be better to take a well studied probiotic first, to reduce the numbers of bad bacteria and then take a prebiotic in time once symptoms have settled; for example, after 3 months of probiotic administration, since the prebiotic will encourage those good bugs in the gut to grow further, perhaps to some point in future when the probiotic may no longer be needed.

Low FODMAP Prebiotics

Prebiotics which have a Monash FODMAP green serve size (see the Monash FODMAP app for the serving) include (6):

Fruits & Vegetables	Grains & Cereals	Legumes, Nuts & Seeds
Artichokes	Oats	Mung beans
Beetroot	Buckwheat kernals	Lima beans
Butternut pumpkin	Wheat free gnocchi	Nuts – almonds & hazelnuts
Pomegranate seeds	Wheat bran	Canned chickpeas
Dried paw paw	Pasta (wheat/spelt), cooked and cooled	Canned lentils

Source: Erin Dwyer, Research Dietitian. Monash University (2016) (6)

Overcoming Low FODMAP Diet Challenges

The table below, formulated by Gut Microbiota For Health by ESNM, describes ways to minimise the challenges of the low FODMAP diet, preferably supported by a registered dietitian specialising in gut health (16).

Challenges of the low FODMAP diet	Guidance for overcoming them
Altered gut microbiota composition.	Incorporate a Bifidobacteria-containing probiotic during the first restriction stage of the low FODMAP diet. Undergo structured and personalised reintroduction of FODMAP-rich foods (ensure the period spent following the first stage is as short as possible).
Compromised nutrient intake (i.e. fibre, iron and calcium) and diet quality.	Optimize intakes of calcium- and iron-rich foods during the restriction stage of the low FODMAP diet. Gradually optimize dietary fibre intake (preferably from food sources) without worsening gut symptoms.
Difficulties with adherence (due to the need for extensive label-reading abilities, high cost of foodstuffs low in FODMAPs and fewer social activities, among others).	The first-line dietary advice in patients with IBS is to follow healthy eating advice. Only when that is unsuccessful in resolving symptoms can the low FODMAP diet be tried with registered dietitian support. Naturally FODMAP-free foods should be encouraged over specialist products in the context of a balanced diet.
Getting caught on the low FODMAP diet for too long and without the supervision of a registered dietitian.	The personalised support of a registered dietitian specialising in gut health is necessary to better follow the low FODMAP diet without incurring nutritional deficits. Supplementary tools such as recipe books and mobile applications cannot replace dietetic advice.
Up to 50% of patients do not respond to the low FODMAP diet.	While the baseline gut microbiota is being explored as a means of predicting the clinical response to a low FODMAP diet, no tests are currently available in routine clinical practice to determine individual response to the low FODMAP diet.

Source: Andreu Prados, GUT MICROBIOTA FOR HEALTH by ESNM (2021) (16)

The first step in the table is similar to my recommendation of taking Alflorex which contains Bifidobacteria first. Although the table states to take Bifdobacteria in the FODMAP restriction phase, personally I recommend a 3 month trial of Alforex prior to starting any dietary restrictions and to continue this during the restriction period. Though many may find they wish to continue with the probiotic after the restriction phase if the probiotic is continuing to provide benefit.

Staying low FODMAP long term is not ideal, since you will be starving your gut flora, reducing bacteria numbers and their diversity. Some prebiotic fibres are better tolerated by IBS patients such as Bimuno (17). This product delivers the GOS FODMAP, but it is derived from milk so may not be suitable for some people. Plus GOS intake can be achieved from canned legumes which have been rinsed.

If you are concerned about not being able to eat broccoli, which contains anti-cancer compounds called glucosinolates, the same compound can be found in swede, which is low FODMAP and contains many other healthful nutrients (18).

Alternative Food Triggers

There may be other components of FODMAP containing foods, that play a role in IBS. These include gluten, amylase trypsin inhibitors and cow’s milk protein that may act as antigens resulting in symptoms in some people. (22)

Additionally, histamine-containing foods (e.g., some fruits and vegetables, oily fish, aged cheeses, alcohol, nuts, eggs, cured meats, and chocolate) have been found to trigger symptoms in almost 60% of IBS patients. This area of potential IBS symptom triggers has not been sufficiently scientifically studied. (22)

Some IBS suffers may suspect salicylate containing foods cause symptoms. It has been shown that IBS patients who reduce dietary salicylates did not improve digestive symptoms compared to a balanced diet high in salicylates. (22)