Supplementing dietary fibres with a low FODMAP diet in IBS


Monash FODMAP team, 05 April 2022

While there has been lots of research looking at the benefits of a low FODMAP diet for reducing gut symptoms, there is also potential for the diet to reduce fibre intake. Reduction in fibre intake can have negative effects on certain aspects of gut health, especially maintaining regular bowel habits.

Fibre supplementation is one way we can address this. However, many common fibres are poorly tolerated by individuals with IBS. A new study by our group investigated whether supplementing specific fibres to a low FODMAP diet would improve bowel habits, without affecting the therapeutic effects of the diet itself.

What kinds of fibres were we interested in?

Sugarcanne bagasse, which is minimally fermented and has bulking properties. This means that it produces very little gas and may offer laxative effects. Resistant starch, which is slowly fermented. This means it produces gas, but at a lesser rate.

There were 3 dietary interventions the lasted 2 weeks each, participants had to complete all 3 interventions:

-          Low FODMAP diet with no added fibre

-          Low FODMAP diet supplemented with 10 g/d sugarcane bagasse

-          Low FODMAP diet supplemented with 10 g/d sugarcane bagasse and 12 g/d resistant starch

The main difference between diets was the amount of fibre participants received and at the time, both researcher and participant did not know which diet they were on. Researchers and volunteers cooked all low FODMAP meals for the participants in a commercial research kitchen. The lead researcher of the trial disguised the extra fibres in breads and cereals that looked identical across each 2-week dietary period.

Who were our participants?

26 participants were recruited from Melbourne Australia. 25 of these were female. 7 had IBS-C (constipation), 8 had IBS-D (diarrhea), 8 had IBS-M (mixed) and 3 were unknown. 6 withdrew from the trial, leaving our final number with 20. Participants were not already following low FODMAP diets before taking in the study.

What did we find?

Across all participants, the three dietary interventions led to improved gastrointestinal symptoms (abdominal pain, bloating, wind) compared with before they took part in the study. Stool volume also increased markedly during the two dietary interventions with fibre supplementation.

Interestingly, we found that in participants who had firm stools or were more constipated, the added fibre helped to soften stools. In those with looser stools, the added fibre helped firm up the stool. This shows us that the fibres could be useful for improving diarrhoea as well as constipation, providing a ‘normalising’ effect.

Most importantly, we found that a fibre, or at least these specific fibres, could be added to a low FODMAP diet without diminishing the diet’s therapeutic benefits. Results like these are exciting and highlight the value that specific fibres can offer to individuals with IBS!

To see the full study, see here.


Daniel So, Chu K. Yao, Zaid S. Ardalan, Phoebe A. Thwaites, Kourosh Kalantar-Zadeh, Peter R. Gibson, Jane G. Muir, Supplementing Dietary Fibers With a Low FODMAP Diet in Irritable Bowel Syndrome: A Randomized Controlled Crossover Trial, Clinical Gastroenterology and Hepatology

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