Fibre blend reshapes gut bacteria in IBS patients without worsening symptoms

A fibre blend combining resistant starch and psyllium husk changed the gut microbiota of people with irritable bowel syndrome (IBS) without aggravating their symptoms, according to researchers at Edith Cowan University (ECU) in Australia. Participants were following a low-FODMAP diet, and they also reported less gut-related anxiety. The randomised, double-blind controlled trial was published in the European Journal of Nutrition.

The problem with restrictive IBS diets

IBS is a common disorder of gut-brain interaction. In Australia, nearly 11 per cent of people are affected. Its cause is not fully understood, though stress, infections and some medications are thought to play a part, and symptoms can be triggered by food, poor sleep, hormonal changes and other lifestyle factors.

A low-FODMAP diet, which restricts fermentable carbohydrates, is a widely used strategy for managing symptoms. The same restriction can reduce beneficial gut bacteria and lower fibre intake over time. Fermentable fibres could in principle help, but in people with IBS they often increase gas and discomfort, so they are usually avoided.

What the team tested

The team at ECU's Nutrition and Health Innovation Research Institute tested a supplement called ur gut, which combines resistant starch with psyllium husk. The researchers propose that psyllium slows the rate at which gut bacteria ferment the resistant starch. More of the starch would then reach deeper regions of the colon before being broken down, which may increase the production of compounds that support intestinal health. This mechanism is presented as a likely explanation rather than something the trial directly proved.

The paper, led by Dr Tina Yan with Professor Amanda Devine, Associate Professor Claus Christophersen and colleagues, reports that participants on the blend did not experience increases in abdominal pain, bloating, diarrhoea or constipation.

Microbiome and anxiety findings

Alongside stable symptoms, the researchers observed marked shifts in the composition of participants' gut bacteria. They described these as large for such a short intervention. Professor Devine said the blend supported bacteria that have been linked to both gut and mental health.

Participants also reported reductions in gut-related anxiety. This is a notable secondary signal, given the close relationship between IBS and psychological stress. The researchers caution that more work is needed to establish whether the benefits extend beyond the digestive system.

Limitations and next steps

Several points should be kept in mind when reading the results:

• The source material does not report the number of participants, the length of the intervention or the exact outcome measures, so the strength of the evidence cannot be judged from it.
• The study showed that symptoms did not worsen, not that they improved. Whether the blend relieves IBS symptoms remains an open question.
• Changes in microbiota composition do not by themselves demonstrate lasting clinical benefit.
• Two of the authors, Devine and Christophersen, are described as co-creators of the supplement, which is already sold commercially. Independent replication would therefore be valuable.

The findings are relevant to dietitians and gastroenterologists because they suggest that dietary management of IBS might aim to maintain microbial health as well as avoid trigger foods. Larger and longer trials, ideally including independent groups, would show whether the microbial and anxiety effects persist after the low-FODMAP phase and whether they translate into better long-term outcomes for patients.

Source: A new fiber supplement could help millions suffering from irritable bowel syndrome (ScienceDaily: health and medicine, 14 November 2026).

Image: AI-generated illustration.