- Design
- Randomised, double-blind, placebo-controlled pilot trial
- Population
- 26 adults with IBS following a low FODMAP diet
- Primary outcome
- Gut microbiota, symptoms, diet, sleep and quality of life
- Effect
- Symptoms stable; microbiota composition shifted (P<0.01); GI-specific anxiety improved (P=0.01)
A small double-blind pilot randomised 26 adults with irritable bowel syndrome already on a low FODMAP diet to a commercial dietary fibre blend or placebo for three weeks.
Symptoms and sleep stayed stable in both groups. The fibre group increased resistant starch intake and showed shifts in gut microbiota composition, including a 5.5-fold rise in one Ruminococcus genus, and improved gastrointestinal-specific anxiety. Faecal and blood biomarkers did not change.
A low FODMAP diet can reduce fibre and alter the microbiota. This tiny, short trial suggests a tolerated way to add fibre back, but it is far from proof of benefit.
- A low FODMAP diet can cut fibre intake; plan reintroduction with a dietitian
- Fibre supplements may be tolerated during a low FODMAP phase, on limited evidence
- Use the low FODMAP diet as a short elimination phase, not a permanent diet
- Soluble fibre such as ispaghula has the best general evidence in IBS
Why it matters
It addresses a known downside of the low FODMAP diet.
Don't overread it
A 26-person, three-week pilot cannot show clinical benefit.
The statistics, in plain English
With 13 people per group, the trial can detect only large effects; microbiome changes are surrogates, not proof of clinical benefit.
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