Irritable Bowel Syndrome and Low FODMAP diet

Irritable Bowel Syndrome (IBS) is a common gastrointestinal (GI) condition wherein the exact cause remains unknown. It is characterized by recurrent abdominal pain, bloating, distension, cramping, flatulence, diarrhoea and/or constipation. It has been proposed that in those with IBS, the nerves that affect perception of intestinal stretching and motility, may have some disturbances secondary to interaction between factors such as genetics, psychosocial and post-inflammatory changes after GI infection. Diagnosis of IBS can be difficult as there is no structural, biochemical or physiological abnormality demonstrated in those with IBS. Thus, IBS diagnosis is based on symptoms reported.


Pharmacological treatment for IBS is tailored and dynamic as symptoms vary in the same individual over a period of time as well as between individuals.


The low FODMAPs diet is one dietary strategy that has been used to manage IBS symptoms. This is considered to be a second line dietary approach after the dietary and lifestyle factors are assessed and managed, as these may contribute to IBS symptoms too. Current evidence suggests that low FODMAP dietary approach (compared to no dietary intervention) can reduce GI symptoms in up to 75% of individuals with IBS. FODMAPs are types of sugar (short-chain carbohydrates) naturally found in foods, which are poorly absorbed in some people or not absorbed at all. FODMAP is an acronym for these sugar molecules and it stands for Fermentable Oligosachharides Disachharide Monosachharide And Polyols.


One can malabsorb either one or a combination of FODMAPs in their small bowel, which then end up in large bowel in undigested forms. This leads to:
a) Increased delivery of water into the large bowel to dilute the concentrated
undigested FODMAPs (as they are osmotically active)
b) Increased gas production secondary to large bowel bacteria feeding on them
c) In turn, bowels expand and their motility is affected (i.e. functioning of bowel
muscles is altered)


In individuals susceptible to IBS, these events could have a combined effect of bowel distension and altered bowel motility causing people to report symptoms like bloating, flatulence, abdominal pain and altered bowel habits (constipation and/or diarrhoea). The low FODMAP dietary approach assists in identifying the potential FODMAP of concern for the individual. Accordingly, a planned and systematic reintroduction challenge of high FODMAP foods will identify which foods can be reintroduced to the diet based on individual’s tolerance levels to achieve symptom relief. It is very important that this is done in consultation with an Accredited Practising Dietitian (APD) to ensure nutritional adequacy throughout the trial and reintroduction phase of low FODMAPs diet.


The implementation of dietary approach can take between 12-14 weeks. It is important to note that long-term restriction of FODMAPs is not recommended as that could lead to nutritional deficiency and may have an unfavourable effect on GI microbiota.

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