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FODMAP Symptoms

The symptoms of FODMAP sensitivity are gut symptoms. 

  • Bloating

  • Stomach cramps/ pain

  • Diarrhoea

  • Constipation

  • Excess wind

You may be more prone to diarrhoea or constipation or go between the two.

These symptoms can also be caused by other issues.....


It is really important that you are diagnosed medically with Irritable Bowel Syndrome (IBS) as these symptoms can overlap with other conditions. In fact there are a number of common diseases that share similar gastrointestinal symptoms to IBS such as Coeliac Disease and Irritable Bowel Disease.

In fact, Coeliac Disease is more common in people with IBS (3.3%) than those in the general population (.3-1%). Appropriate treatment of CD will for the majority of cases resolve the IBS symptoms (1).


Consequently, there is a risk of misdiagnosis and that other diagnosis are missed. For example endometriosis may be missed (up to 16% chance) and coeliac disease (up to 5% chance). With improved diagnostic capabilities, a misdiagnosis of Irritable Bowel Disease (including microscopic colitis) now occurs in a much smaller proportion of patients (approximately 1- 4 % of IBS patients). There is also a small chance of missing gastrointestinal cancers, ovarian cancers, diverticular disease, pelvic floor disorders, endocrine disorders and pancreatic exocrine insufficiency (1).

So go to your doctor and have a medical work up before deciding to go on a low FODMAP diet.


FODMAP symptoms are largely confined to the gut as this is where the problems are occurring. Extra reactions such as rashes or migraines are not FODMAP issues but more likely to be other food intolerance reactions. If this is your case, you may benefit from discussing this with me to see if food chemical sensitivity is a better option.


To make things confusing, food chemical sensitivity can also cause gut symptoms such as gut pain, bloating, excess wind, constipation and diarrhoea so if a low FODMAP diet does not resolve the issues then food chemical sensitivity could be explored.



FODMAP issues start higher up in the gut (the small intestine) where the smaller osmotically active FODMAPs (fructose, lactose and polyols) attract water into the gut and then continue into the large intestine where our friendly gut bacteria ferment the FODMAPs and trigger the symptoms.

People suffering from IBS (Irritable Bowel) will have a hypersensitivity to the FODMAP fermentation by the gut bacteria which after eating causes significant bloating,  gut pain, constipation, diarrhoea or alternating between the two, excessive wind and borborygmi (gut noises).

As the gut is 7 1/2 - 8 1/2 metres long, it takes a while for the FODMAPs to reach the large intestine where fermentation occurs. This takes about 4 - 24 hours (or even more) for the food and drink consumed to travel through the gut and reach the large intestine.

There are few cases where symptoms can be felt sooner, for example taking a high lactose load on an empty stomach but generally this is not the case.

What can actually happen is eating can cause the next bit of food lying in the gut to move onto the next section. So eating could cause intestinal contents reflected a food eaten a day or two days ago to be pushed into the large intestine where fermentation and gut symptoms may then quickly occur.

Rather than attributing gut pain or symptoms to a food just eaten, you may need to look what you have eaten over the last couple of days. This is particularly true for foods containing oligosaccharides such as onion and garlic.

Reducing FODMAPs has been shown to help 75% of IBS sufferers within 6 weeks. However, most people will find symptom improvement within within days or a week!


  1. Monash University Dietitian Low FODMAP for IBS training course, January 2018

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