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What Food Should You Avoid On A FODMAP Diet?


Be prepared – the list of foods that can cause you to demonstrate an intolerance is pretty huge. Working out what you should and shouldn’t eat to alleviate symptoms is difficult and can consist of whole groups of food, or single items from one group or several groups.

You may wonder what FODMAPs are – they are small groups of carbohydrates that are indigestible to some people. Because they ‘refuse’ to break down, they then cause uncomfortable symptoms such as bloating, gas, diarrhoea, constipation and stomach cramping. The prospect of living with it can cause distress and make you extremely miserable. This is probably the simplest way of describing it.

The first step really is to consult your GP and ask him what he thinks. He may suggest tests before you embark on the low FODMAP system. He may be relaxed about it and suggest that if you have any ideas of what is causing it, that you should create a food diary, listing everything you eat and seeing if certain foods cause you grief when you consume them. You need to find a potential pattern, then gradually cut out the foods that compromise your digestion more often than not. It’s tricky to start, but by no means impossible to get results quickly, but you must record everything carefully.

Is there a relationship between FODMAPs and IBS?

The most common reason for needing to change your diet is undoubtedly IBS, an embarrassing condition that can leave you feeling isolated and not wanting to go too far from a bathroom. Around 4 million food intolerance sufferers find IBS a direct result of their discomfort, so it really is worth the effort to lessen the effect. Make no mistake though – IBS is a lifelong condition, but you can do things to improve it and make it liveable with. However, there can be several causes of IBS and other digestive issues which need to be ruled out, before commencing any form of dietary control.

Don’t quite understand low FODMAP?

Trying to explain FODMAP is quite difficult, but we have tried to simplify it as much as possible. Not everything is known about FODMAP, in fact, in comparison to other diet-related diseases, scientific studies are very limited. But here goes, as simply as possible:

Firstly, what does FODMAP actually stand for and examples?


F = Fermentable

When gut bacteria break down undigested FODMAPS to produce gases.


O = Oligosaccharides

Split into 2 different groups – FOS found in fruit and veg, flowering plants such as chicory. GOS found in food items such as legumes, soy milk (made from whole beans), oat milk, some nuts such as pistachios and a variety of other fruit and vegetables.


D = Disaccharides

3 most common – lactose, maltose and sucrose. Commonly found in milk, fruits and vegetables.


M = made up of fructose, galactose, and glucose.

High fructose means high FODMAP. Apples, asparagus, mango, orange juice and lots more may cause a reaction. The sweeter something tastes, generally the higher the fructose.


A = And…

P = Polyols

A high FODMAP count can be caused by sugar alcohols and result in strong gastro problems. Products containing isomalt, maltitol, mannitol, sorbitol and xylitol are some of the culprits. You may have heard of the latter, as it is used as an ‘artificial sweetener’. The others can also be used in artificial sweeteners but are not so well known.

If you are in fact disturbed by any of the above groups, you will find out somewhere between 6 and 24 hours later (where fermentation takes place in the colon, satisfactorily or not) and the symptoms manifest themselves.

It can be very worthwhile trying a low FODMAP diet, but not without consulting your medical professional first. They may well refer you to a registered dietician, once any possibilities of underlying illnesses have been ruled out. A registered dietician is valuable when suffering from IBS or anything related to food intolerances, and far more acceptable than reading advice from untrusted sources on the web.


Bacteria and the importance of fermentation

The digestive system is home to trillions of bacteria, some ‘good’ and some ‘bad’. It can vary from person to person. When the good bacteria are low in count, this is when problems can begin.

When you eat, you are also feeding the resident bacteria, so your diet should be based on good bacteria to prevent or lessen the effect of any non-fermentable items. This is why dieticians will recommend a low FODMAP diet. When you eat carbohydrates, they need to be broken down by enzymes to enable food to travel through the small intestine and into the large intestine, also called the colon. The good or friendly bacteria will also act to kill off the bad bacteria to allow the digestive process to take place. If you have an imbalance, this is when your gut does not perform correctly.

The good news on the horizon is that scientific results have demonstrated that around 70% of adults experience an improvement in their IBS once following the low FODMAP diet. However, please note that there is no concrete proof that this diet will act on other digestive issues, more testing must be done.


It’s worthwhile remembering the following points:

  • The diet is ‘low and not ‘no’. Never think about cutting out carbohydrates completely, they are beneficial if you moderate them.
  • Low FODMAP is neither gluten-free nor dairy-free, so if you have a gluten intolerance or dairy intolerance this is something to bear in mind. There will still be things you can tolerate or not, depending on your tolerance level.

It is wise not to maintain the low-FODMAP period over any length of time (recommended is up to 8 weeks for the introductory period). Always keep in touch with your dietician.

Whilst you can still glean almost all of the nutrition you need from a low FODMAP diet, you can sometimes show a small deficiency. The most likely deficits will be those of fibre and/or calcium. A dietician will be able to help you with any adjustments required.

We’ve created a full set of recipes including, low FODMAP breakfast recipes, low FODMAP lunch recipes, and low FODMAP dinner recipes. They’re a great way to get started on low FODMAP diets and we’ve included everything from the ingredients to the recipe methods.

Please also note that whilst you should seek the advice from your GP, they will not necessarily know everything regarding specific diets. They are likely to refer you to an experienced dietician, but your doctors’ surgery should always be your first point of call. You can also take an at-home advanced intolerance test to run a preliminary scan.

Sian Baker

Medically reviewed by Sian Baker, Dip ION mBANT mCNHC – Written by Beth Giddings.