If you’re suffering from gastrointestinal symptoms or if you’ve been diagnosed with irritable bowel syndrome (IBS), you might have heard of the low FODMAP diet.
This diet is recommended for people who suffer from IBS to relieve and manage uncomfortable and debilitating gastrointestinal symptoms. Studies show that around 75% of people with IBS see symptom improvement on the low FODMAP diet.
Although the low FODMAP diet is effective for managing IBS symptoms, it can be restrictive and challenging to follow. Therefore, it is recommended that people try the low FODMAP diet with the help of a dietitian.
What is the low FODMAP diet and what are FODMAPs?
Around 60% of people who have IBS report that their diet impacts on their symptoms. The low FODMAP diet can help to pin-point which foods might be the culprits by identifying if any fermentable carbohydrates (sugars) are setting off symptoms.
FODMAP stands for Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols which are types of fermentable carbohydrates. These fermentable carbohydrates are not digested very well by your body and so they pass through your digestive system relatively intact.1 During this time, the FODMAPs draw water into your digestive system.2 When the undigested FODMAPs enter the large intestine they are fermented by the bacteria that naturally live there. During the fermentation process the bacteria produce gas and other by-products.2
The combination of increased water, gas and by-products created by the bacteria can be problematic if you have IBS. This is because people who have IBS have sensitive nerve endings in their intestines. The water, gas and by-products build up and can cause uncomfortable and painful symptoms like abdominal pain, bloating, gas, diarrhea and constipation.1, 2

How does the low FODMAP diet work?
The low FODMAP diet works by temporarily reducing your FODMAP intake to see if your symptoms improve. If your symptoms improve it can help you to identify exactly which FODMAP groups are the problem. Once you know which FODMAP groups are an issue you will be able to tailor your diet long term to help:
Manage your symptoms.
Increase the variety of foods in your diet.
Improve your overall quality of life.
Who should try the low FODMAP diet?
If you have ongoing gastrointestinal symptoms it is important to be thoroughly checked over by your doctor before starting the low FODMAP diet (or any other diets including a gluten free diet). The symptoms of IBS can be very similar to symptoms of many other disorders.
Once you have ruled out other medical conditions as a cause for your symptoms it is best to first touch base with a dietitian before starting the low FODMAP diet. Sometimes other smaller diet changes can be made to improve your symptoms. If small diet changes are not effective your dietitian will probably then recommend trying a low FODMAP diet next.
The low FODMAP diet in three steps
The low FODMAP diet has three steps which you should work through with the help of your dietitian.
Step one: low FODMAP diet
During this first step you remove all high FODMAP foods from your diet for 2-6 weeks to see if your symptoms improve. If your symptoms improve you will move on to step two: FODMAP reintroduction.
Many people think that if they feel better during step one they don’t need to move to the next step. Although you might be feeling better, the low FODMAP diet is only meant to be temporary. It can unnecessarily restrict your overall diet, impact on the diversity of your gut bacteria and be associated with developing disordered eating patterns.
Step two: FODMAP reintroduction
Step two: FODMAP reintroduction lasts for 8-12 weeks. You will complete food challenges so that two things can be tested:
We want to know which FODMAP groups you are sensitive to and which you can tolerate.
We want to know how much (or the quantity) FODMAP you can eat without getting significant symptoms.
Each food challenge lasts for 3 days with a 3-4 day break between challenges. Each FODMAP group is tested individually so that you can get an accurate result.
Step three: FODMAP personalisation
Once you have completed the FODMAP reintroduction phase you are at the last step: FODMAP personalisation. The aim of this step is to give you the greatest amount of flexibility in your diet while avoiding foods that cause significant symptoms. The results from the food challenges will help to achieve your personalised, long-term diet.
Examples of FODMAPs in foods
FODMAPs are found in many foods:
Oligosaccharides: wheat, rye, onion, garlic, legumes/beans, cashews, pistachios
Disaccharides: milk, yoghurt, ice cream, cream, some soft cheeses (ricotta, cottage cheese)
Monosaccharides: apples, mango, pear, figs, fruit juice, some dried fruit, honey
Polyols: stone fruits, blackberries, cauliflower, mushroom, some artificial sweeteners
Some foods only contain one type of FODMAP but many foods contain multiple FODMAP groups. For example, watermelon contains oligosaccharides, monosaccharides and polyols. This can be an area where many people go wrong as they will reintroduce foods with multiple FODMAPs, have a reaction but from this we can't tell which FODMAP you have reacted to. Therefore it is important when reintroducing each FODMAP we are choosing foods with only one FODMAP per test to obtain clear results.

What if the low FODMAP diet doesn’t work for me?
Unfortunately, the low FODMAP diet doesn’t work for everyone. Around 25% of people who follow the low FODMAP diet will not see significant symptom improvement. If this is the case, there are other strategies you can try to help manage your IBS. Our dietitians can assist you in identifying these options and get you back to living life without being limited by your IBS.
Final thoughts
The low FODMAP diet can be an effective option to manage your IBS. It is not meant to be a long-term diet but instead can help you to identify and avoid your food triggers.
Before starting a low FODMAP diet we recommend seeing your doctor to rule out other medical conditions and then coming to see one of our specialised gut health dietitians at Dietitians NT for personalised support. We offer appointments for people in Darwin, Palmerston and around Australia.
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