2020-09-14 11:17:33

IBS - What is it?

Bloating, gas, abdominal distention, diarrhoea, constipation, pain; these are just some of the symptoms associated with IBS. It is a chronic disorder with symptoms that come and go and vary in severity. The symptoms can have a significant impact on quality of life, leading to fear of travel and long journeys, increased sick days, negative effects on relationships, social isolation and increased depression and anxiety. This contributes to an overall increase in anxiety experienced by individuals with IBS and perpetuates the cycle.

The cause of IBS is unclear, but it appears that sufferers have an incredible sensitivity to normal messages that are sent to the brain from the gut. We’ve all heard about the gut-brain link and essentially, messages from the gut regarding changes in gut volume (stretching of the wall), speed of movement of food through the gut and the chemical compounds in food get sent to the brain and are incorrectly interpreted in the brain as pain. But it is not only about messages from the gut to the brain, the brain can also send messages to the gut so that stress or anxiety can independently trigger IBS symptoms. Stress reduction techniques such as yoga, meditation and exercise are therefore essential in IBS treatment.

Given that IBS symptoms overlap with other more serious medical conditions such as coeliac disease, inflammatory bowel disorders (Crohn’s disease and ulcerative colitis) and endometriosis, it is important that these are excluded before IBS is diagnosed. After excluding them, IBS is diagnosed based on symptom presentation using specific criteria.

Treating IBS with dietary management

Because food intake is often seen as a trigger for symptoms, surely cutting out everything that triggers symptoms can help? The problem is that long term unnecessary restriction can have far reaching, negative health consequences associated with nutrient deficiencies.

Dietary factors that are typically associated with IBS symptoms include fat, certain proteins in milk (β-casein) and grains (gluten), caffeine, alcohol and fermentable carbohydrates. While there have been a number of dietary approaches to help to control IBS symptoms, many of these diets have had limited success as they tend to focus on one aspect at a time rather than comprehensively addressing all potential contributing factors. This is where the low FODMAP diet has come into play.


There is a group of carbohydrates known as fermentable carbohydrates which are often poorly digested and absorbed and so end up in the small intestine. There, they attract water into the gut, increase fermentation by gut bacteria causing gas production, trigger diarrhoea or constipation and cause abdominal pain. These carbohydrates have been termed FODMAPS (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) and are found in a wide range of different foods (e.g. fruit, vegetables, legumes, grains and dairy).

Monash University has been involved in research in FODMAPS over the past few years and has refined the low FODMAP diet. The overall goal of this approach is ultimately to devise an individualized, minimally restrictive diet that significantly reduces symptom severity and improves overall quality of life i.e. avoids restricting food unnecessarily.

In order to do this the low FODMAP approach involves 3 key steps:

  1. Low FODMAP diet (4-6 weeks) - removes all FODMAPS from the diet to assess if this relieves IBS symptoms (i.e. are FODMAPs involved in triggering IBS symptoms?)
  2. Reintroduction of FODMAPs (6-8 weeks) - FODMAPS are gradually re-introduced into the diet to identify the individual’s sensitivity to specific FODMAP subgroups and at what dose/serving size (i.e. which particular fermentable carbohydrate is this individual sensitive to and how much is tolerated?)
  3. FODMAP Personalization - to expand the diet based on the individual’s tolerance (i.e. to devise a personalised diet based on the individual’s tolerance balancing minimal restriction and maximal symptom reduction).

Why one shouldn’t just follow a low FODMAP diet long term?

Phase 1 of the low FODMAP diet restricts all foods that contain these fermentable carbohydrates and as such may restrict particular food groups resulting in the diet being nutritionally deficient. Nutrients of concern include calcium, iron, fibre and natural prebiotics. Many of the FODMAP foods are sources of fermentable fibre which acts as a natural pre-biotic promoting the abundance of beneficial gut bacteria. Studies have shown that phase 1 of the low FODMAP diet results in decreases in numbers of the beneficial bacteria in the gut and increases in the less beneficial bacteria. Over the long term this can lead to increased health risks. These changes are however reversible and as such completion of Phase 2 and 3 are actively encouraged. Furthermore, through this approach it is possible to help the individual to better understand how to manage IBS symptoms without following an overly restrictive diet that impacts food choice, flexibility and ultimately quality of life, particularly in social settings.

The Low FODMAP approach to IBS symptom management should be carried out under the guidance of a registered dietitian who has training and understanding of this approach. Ultimately the final diet should be nutritionally complete with minimal restrictions while optimally managing IBS symptoms. It should also be remembered that IBS symptoms and symptom severity may change over time and this may require ongoing challenges to determine if restricted foods can be included in the diet.