Troubleshooting on the Low FODMAP Diet

Troubleshooting on the Low FODMAP Diet

Written by Melinda Braithwaite (Accredited Practising Dietitian) from Lifestyle Nutrition.

Have you been following a low FODMAP diet but are finding your gut symptoms are still not improving? This is can be very frustrating and disheartening, however before you give up hope it can be worth having another look over your diet and considering medical and lifestyle factors. 

Check you are using up-to-date and reputable FODMAP guides

When it comes to FODMAPs and food lists there is so much information on the internet. Unfortunately many of these lists are often incorrect or contain outdated information. I recommend using the Monash University low FODMAP diet guide book and Monash app as they continually update their information as they test foods. The FODMAP friendly app can also be useful as they also undertake FODMAP food testing and certify food products.

Check portion sizes

If you are not responding to a low FODMAP diet it is important to double check your portion sizes using the Monash University low FODMAP diet guide booklet or app. Several low FODMAP foods can become high FODMAP if you exceed the recommended portions. It also worth noting that fruit should be limited to 1 serve of low FODMAP fruit per meal/snack to avoid the FODMAP content becoming high. I often recommend a fruit serve in the morning and then another fruit serve in the afternoon or evening.

Check for hidden high FODMAP ingredients in packaged foods

It is important to check all packaged food for potentially high FODMAP ingredients. Some of the most common high FODMAP ingredients which I see accidently consumed include soy flour, chickpea/besan flour, chicory root/inulin, fruit juice concentrate and honey. Also check products do not contain sweeteners such as mannitol, sorbitol, xylitol, isomalt, malitol and lacitiol. Lastly, be on the lookout for stocks and pre-made sauces with vegetable powder or dehydrated vegetables listed as an ingredient as these may contain onion or garlic.

Assess fibre intake

Both excessive fibre and low fibre intake can contribute to IBS symptoms (1, 2). Often on a low FODMAP diet fibre intake does reduce as many high-fibre grains, fruit and vegetables are reduced or eliminated. This does have the potential to aggravate symptoms especially constipation. It is a good idea to check your fibre intake. Both the Monash University FODMAP guidebook and app include fibre counters. The recommended intake is 25g fibre/day for women and 30g fibre/day for men. If fibre intake does need to increase research has shown that soluble fibres such as oats and psyllium are generally better tolerated (1, 2). Studies have also shown that 1-2 tablespoons/day of linseeds may be effective at reducing bloating and wind (1, 2). It is important to ensure adequate fluids when increasing fibre to prevent constipation.

Check your diet for other non FODMAP food triggers

Several non FODMAP food triggers can also cause IBS symptoms. Potential triggers include alcohol, caffeine, carbonated drinks, fatty foods and spicy foods (1, 2). These non FODMAP triggers can cause changes in the gut such as altered gut motility. It is worth assessing your intake and potentially reducing these triggers if you feel they could be contributing to your symptoms. In addition long gaps between foods or missed meals may also aggravate IBS symptoms so ideally ensure regular small meals.

Consider other potential food intolerances

If you are not responding to a low FODMAP diet and have taken into account other IBS triggers it may be a good idea to discuss with your health professional whether you have a non-FODMAP related food intolerance. This can be easier to identity if you have been keeping a food symptom diary. In some instances a low food chemical diet reducing salicylates, amines, glutamates and some food additives may be indicated especially if you have additional symptoms such as fatigue, headaches/migraines, mouth ulcers, hives or sinus congestion.

Check any current medications and supplements for potential gut side effects

Several medications and supplements can cause IBS like symptoms. Several pain medications and iron supplements can often cause constipation and stomach upset (3). On the other hand antibiotics, metformin (common diabetes medication), non-steroidal anti-inflammatories and magnesium supplements can cause diarrhoea, stomach upset and nausea (3). If you feel your medication or supplement may be affecting you I would recommend speaking with your GP or health professional.

Consider if stress is affecting your IBS symptoms

Stress is well known to contribute to IBS symptoms. Stress can reduce blood flow to the gut, reduce gut motility and increase gut sensitivity. If you are struggling with stress it is important to try to address this and incorporate some stress management techniques that will work for you. 

In conclusion, if you are finding the low FODMAP diet is not working for you I would recommend speaking with your health care professional. I would also recommend working under the guidance of a dietitian who specialises in IBS and gut health to work out the best approach forward for you.


  1. McKenzie YA, Bowyer RK, Leach H, Gulia P, Horobin J, O'Sullivan NA, Pettitt C, Reeves LB, Seamark L, Williams M, Thompson J and Lomer MCE. British Dietetic Association systematic review and evidence‐based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update). Journal of Human Nutrition and Dietetics 2016; 29(5): 549.757.
  2. National Institute for Healthcare and Excellence. Irritable bowel syndrome in adults: Diagnosis and management clinical guideline. Published 2008, updated 2017. Available from
  3. Stewert R. Griffin handbook of clinical nutrition and dietetics 4th edition. Queensland: Rowan Stewert, 2012.

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