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FODMAP elimination diet: have I got a food intolerance?


Why are low FODMAP diets and food elimination diets becoming increasingly popular? Food intolerances seem to be on the rise: supermarket aisles are forever expanding with new free-from product ranges. Bloating, stomach aches and other digestive discomforts are incredibly frustrating – often, we’re programmed to think that an intolerance is the culprit behind such symptoms, leading many of us to avoid certain foods unnecessarily. 

It is indeed unadvisable to self-diagnose yourself with an intolerance without any conclusive evidence, which is why we’re here to advise you on what you can do if you suffer chronically from unpleasant symptoms, such as nausea, bloating, stomach aches or diarrhoea.

You'll be pleased to learn that there are ways to identify the source of your discomforts – whether it’s through a combination of methods or just one. Read on to find out more about elimination diets – more specifically the FODMAP elimination diet – intolerance IgG blood tests and more!

How does a food intolerance elimination diet work?

Elimination diets are short-term diagnostic diets used to identify foods to which you may be sensitive or intolerant, such as lentils, eggs or gluten. The point of an elimination diet is to avoid a certain food for around one month in order to see if symptoms improve. If there is an improvement, you can then deduce which foods you are less able to tolerate. 

Food intolerance elimination diets require a lot of motivation. Criticism that accompanies elimination diets includes the following:

  • they are often not strictly adhered to
  • many people do not ensure that they receive sufficient nutrients and vitamins elsewhere when they choose to eliminate an important food[1]

Please note: For breastfeeding mothers, it is particularly crucial that there are no nutrient deficiencies resulting from eliminating a certain food group.[1] To find out more about the ideal diet during pregnancy and breastfeeding, visit our Health Portal article.

When to do a food elimination diet

Healthcare professionals, such as nutritionists, gastroenterologists and allergists, are likely to recommend that you introduce an elimination diet if you have ruled out coeliac disease or a lactose or fructose intolerance with the relevant intolerance test. Once you have established with a professional the food you wish to eliminate, plus how to monitor your symptoms, you should introduce your new diet plan.

Dieticians or nutritionists may also help you figure out how to interpret certain packaging labels to make sure that the food you consume and buy is suitable for you.[2]

Does an elimination diet help with food intolerances?

Medical professionals often recommend trying an elimination diet as one of the most reliable ways of food intolerance testing. The NHS, for example, suggests eliminating certain foods from your diet and visiting a dietician if symptoms persist after the reintroduction phase. There are, of course, other ways you can test for food intolerances, many of which could complement the results of a food elimination diet well.

banner to food intolerance and food allergy test

What do you eat on an elimination diet?

Perhaps the question should rather be What do you not eat on an elimination diet?’. What you choose to eliminate from your diet varies greatly from person to person. We recommend talking with a dietician to determine which foodstuffs you should avoid as part of your elimination diet. Generally, however, you should aim to avoid any food to which you may be hypersensitive or intolerant.

You might also consider removing foods from your diet that commonly trigger symptoms such as bloating, diarrhoea and stomach pains. Such foods may include nuts, soy, dairy, certain fruits and vegetables, wheat, gluten, eggs and seafood.

A very specific type of food elimination diet that has gained attention over recent years is the FODMAP elimination diet, which involves avoiding staple everyday foods such as onions, garlic, ripe bananas and mushrooms.

What is the FODMAP elimination diet?

FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are natural substances found in many foods. However, they can cause digestive problems. They are short-chain carbohydrates such as fructose and galactose (monosaccharides), lactose (disaccharide) and fructans (oligosaccharide) as well as mannitol and sorbitol (polyols).

These sugars and sugar alcohols are poorly absorbed in the small intestine and enter the large intestine where the bacteria living there ferment them. This means that they are converted by our gut bacteria – our gut microbiome – which produce gases and short-chain fatty acids. These short-chain fatty acids have many health benefits, but a very high concentration can also cause discomfort and bad gut health. These gases can lead to bloating, abdominal pain and diarrhoea or constipation.[3]

low-FODMAP foods

What are the worst FODMAP foods?

Individual foods can be divided into high and low FODMAP foods. For example, grains such as wheat, rye, barley and spelt contain many FODMAPS, whereas rice, oats, corn and quinoa contain only a few FODMAPs.

Milk and dairy products contain many FODMAPs, which is why a low-FODMAP elimination diet involves consuming lactose-free or plant-based milk alternatives, such as almond, hemp or coconut milk.

Vegetables vary greatly in their FODMAP content. For example, artichokes, asparagus, cabbage, onions and garlic contain abundant FODMAPs. Carrots, spinach, cucumber and aubergines, on the other hand, are low in FODMAPs. The same applies to fruit. Large portions of fruit should generally be avoided in a low FODMAP diet.

Legumes such as chickpeas, lentils and beans are high in FODMAPs – only tofu (made from soybeans) and peanuts are low in FODMAPS. Sweeteners such as honey, agave and corn syrup are high in FODMAPs. Dextrose, ordinary table sugar or even maple syrup provide few FODMAPs. Nuts and seeds are also often high in FODMAPs – especially pistachios.

Eggs, fish and meat do not usually contain FODMAPs. The exception is some canned fish and sausages that contain additives.[6, 7]

How to do an elimination diet for IBS

On a low-FODMAP elimination diet, you avoid foods that contain FODMAPs – this is to relieve digestive symptoms. This diet is usually recommended for people with irritable bowel syndrome – also known as IBS.

However, there are currently no uniform dietary recommendations for the treatment of IBS. The dietary recommendations are specifically based on individual symptoms. If IBS is associated with symptoms such as frequent abdominal pain, bloating and diarrhoea, a diet low in FODMAPs could be a useful form of treatment. Before you change your diet, however, you should definitely rule out coeliac disease as well as a wheat allergy and possible food intolerances.[6, 7]

A low-FODMAP elimination diet should primarily be seen as a diagnostic test. Together with a food intolerance test and a nutritionist, you can check whether your intestine reacts positively when you reduce your FODMAP intake. Seeing a nutritionist will ensure that you avoid possible nutrient deficiencies. The reactions to FODMAP-rich foods vary from person to person and should be closely monitored. Therefore, switching to a low FODMAP diet is divided into three FODMAP elimination phases.[9, 10]

What are the FODMAP elimination phases?

A change in your diet should always be implemented gradually. This way, you can recognise and be aware of your body’s reactions. You will find out which amounts of FODMAPs you can still tolerate well and how you can skilfully incorporate them into your diet.

FODMAP elimination phase 1

The first phase of a low FODMAP diet is the elimination phase. Over a period of about four to six weeks, you should strictly reduce FODMAP-containing foods to relieve symptoms. 

Keep a food diary: in order to recognise certain triggers of your symptoms as well as the severity and duration of your discomfort, you should keep a diary. In it, you should record which foods you eat every day. Make a note of existing symptoms and rate their severity on a scale – for example, 0 = no symptoms to 10 = very severe symptoms.

Did you know that other stimulants such as alcohol, nicotine and caffeine or your meal times can also trigger irritable bowel syndrome? You should also record the consumption of these stimulants in your diary.

FODMAP elimination phase 2

The second phase begins when you notice an improvement in your symptoms. If you don’t experience any change in the severity of your symptoms, you should check other possible triggers – for example, stress, portion sizes or spices.

FODMAP foods that were not consumed during the elimination phase are gradually reintroduced in the second phase. It is important to test one FODMAP at a time, once a day, for several days. For example, if you reintroduce fructose, you can have honey once a day.

You should also continue updating your food diary with your meals and symptoms. In this test phase, you first find out how much of – for example – fructose-containing foods you can tolerate. Afterwards, other FODMAPs can be tested: lactose, for example, by eating milk; sorbitol with apricots; and mannitol with mushrooms.

FODMAP elimination phase 3

In this FODMAP elimination phase, you’ll learn how to reintroduce FODMAPs back into your diet. This is where you set a long-term diet plan. The main goal is to eat with as few restrictions as possible. In the test phase, you have found out which foods you tolerate well and which you tolerate less well and which quantities are suitable for you in each case. This is the basis for your long-term diet! If you have to completely avoid some FODMAP-containing foods, it is especially important to find suitable alternatives.[8, 13]

Fodmap elimination phase

How long should a low-FODMAP elimination diet last?

How long you should follow a low FODMAP diet is not exactly set in stone. The phases of your dietary changes are always based on your individual symptoms. In the best case, your low-FODMAP elimination diet plan will cause you no to little discomfort and will allow you to consume all important nutrients, such as sufficient protein and micronutrients such as iron and vitamin C. If this is successful, you can maintain this diet in the long term!

It is absolutely crucial that your long-term diet does not lead to any nutrient deficiencies – if you are unsure or would like to double-check that your nutrient levels are optimal, you can take various vitamin deficiency tests or nutrient deficiency tests. If you don’t regularly check your nutrient levels, this could lead to serious health effects in the long run.

FODMAPs and elimination diets – at a glance

How does a food intolerance elimination diet work?

Food intolerance elimination diets are seen as diagnostic tests used to identify foods that may be causing you discomfort when you digest them. Symptoms include flatulence and bloating, cramping and stomach pain. The aim of an elimination diet is to avoid a certain food for around four to six weeks in order to see if symptoms improve. If there is an improvement, you can then identify which foods you are less able to tolerate. 

What do you eliminate?

You should eliminate any foods you suspect may be the trigger for your discomfort. If you’re unsure which food is causing you problems, discuss eliminating common problematic foods with a nutritionist or dietician.

What is a FODMAP?

FODMAPs are short-chain carbohydrates, such as fructose, lactose, fructans, or even mannitol and sorbitol. These natural substances are found in many foods. They are poorly absorbed by our small intestine and therefore reach the large intestine, where they are then fermented. This can lead to increased symptoms such as bloating, abdominal pain or even diarrhoea and constipation.

Can elimination diets help with food intolerances?

Elimination diets are widely recommended by medical professionals and nutritionists as a way to spot a food intolerance or sensitivity. By avoiding foods you believe you might be sensitive to, such as FODMAP foods, you can determine just how intolerant you are to certain foods if you find that symptoms improve whilst on the food elimination diet.


[1] Urisu, A., Ebisawa, M., Mukoyama, T., Morikawa, A., Kondo, N. 'Japanese Guideline for Food Allergy: Review Article’ Allergology International, vol. 60(2), 221–236, 2011, doi:10.2332/allergolint.11-RAI-0329.

[2] NHS 'Diagnosis: Food allergy’ April 2019, available at https://www.nhs.uk/conditions/food-allergy/diagnosis/, accessed on 9 March 2021.

[3] PTAheute, Nervöser Darm – was verbirgt sich hinter dem Reizdarmsyndrom? | PTAheute’. available at https://www.ptaheute.de/news/spezial/wissen-am-hv/magen-darm-beschwerden/nervoeser-darm-was-verbirgt-sich-hinter-dem-reizdarmsyndrom/, accessed on 7 July 2020.

[4] Deutsche Apotheker Zeitung, Darm in Aufruhr’, DAZ.online, March 2017, available at https://www.deutsche-apotheker-zeitung.de/daz-az/2017/daz-13-2017/darm-in-aufruhr, accessed on 7 July 2020.

[5] Deutsche Gesellschaft für Ernährung e. V., Ernährungstherapie bei Reizdarmsyndrom’, available at https://www.station-ernaehrung.de/fachinformationen/spezielle-kostformen/reizdarmsyndrom/ernaehrungstherapie/, accessed on 30 July 2020.

[6] Halmos, E. P., Power, V. A., Shepherd, S. J., Gibson, P. R., Muir, J. G. A Diet Low in FODMAPs Reduces Symptoms of Irritable Bowel Syndrome’, Gastroenterology, vol. 146(1), 67–75.e5, 2014, doi:10.1053/j.gastro.2013.09.046.

[7] Gravina, A. G. et al., Adherence and Effects Derived from FODMAP Diet on Irritable Bowel Syndrome: A Real Life Evaluation of a Large Follow-Up Observation’, Nutrients, vol. 12(4), 2020, doi:10.3390/nu12040928.

[8] Deutsche Gesellschaft für Neurogastroenterologie und Motilität e.V. und Deutsche Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselkrankheiten,Update S3-Leitlinie Reizdarmsyndrom’, 2020.

[9] Bellini, M. et al., Low FODMAP Diet: Evidence, Doubts, and Hopes’, Nutrients, vol. 12(1), 2020, doi:10.3390/nu12010148.

[10] Reese, I. Low-FODMAP-Diät’, Ernährungs Umschau, 11 April 2018, https://www.ernaehrungs-umschau.de/print-artikel/11-04-2018-low-fodmap-diaet/, accessed on 7 July 2020.

[11] Schumann, D., Klose, P., Lauche, R., Dobos, G., Langhorst, J., Cramer, H. Low fermentable, oligo-, di-, mono-saccharides and polyol diet in the treatment of irritable bowel syndrome: A systematic review and meta-analysis’, Nutrition, vol. 45, 24–31, 2018, doi:10.1016/j.nut.2017.07.004.

[12] Schmidt, A., Hofer, J.-H., Bästlein, C.,FODMAP – Richtig essen bei Reizdarm’, 2015.

[13] Maissen S., Kiss, C. FODMAP-Konzept: Praktische Umsetzung und Fallbeispiele’, 6.

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