Inulin and gut bacteria in people with mild constipation
What it found
Taking 12 g of inulin daily for four weeks changed the levels of three types of gut bacteria in healthy adults with mild constipation.
The drop in one type, Bilophila, was linked to softer stools and feeling better.
What they found
Studies in people
Three bacteria shifted
Inulin raised the amounts of Bifidobacterium and Anaerostipes in the gut. It lowered the amount of Bilophila. No other bacteria groups showed consistent changes.
Softer stools and comfort
When Bilophila levels dropped after taking inulin, participants reported softer stools. They also felt less physical discomfort and were more satisfied with how their constipation was managed.
Stool chemicals unchanged overall
The researchers looked at 382 volatile chemicals in the stool samples. Taking inulin did not change the overall pattern of these chemicals compared to the placebo.
One chemical rose
Only one chemical, called dodecanal, was found in higher amounts after people took inulin. Its rise tracked with the increases in Bifidobacterium and Anaerostipes.
Overall gut variety dipped slightly
The total number of different bacteria types seen in stool samples went down a little during the inulin period. This small drop did not match up with changes in how often people went to the toilet or how firm their stools were.
What the authors conclude
- They conclude that inulin selectively changes just a few types of gut bacteria rather than shifting the entire community.
- The authors note that the drop in Bilophila is linked to improved comfort and softer stools, making it a promising focus for future research.
- They suggest this selectivity could help tailor dietary interventions to target specific gut imbalances.
How it was done
Scientists wanted to see if inulin changes only a few specific gut bacteria or shifts the whole bacterial community. Earlier work in mice suggested broad changes, but this had not been checked fully in people.
Forty-two healthy adults with mild constipation took part in a trial where each person tried both treatments. They took either 12 g of chicory-derived inulin or a placebo every day for four weeks, with a break in between. Researchers then tested their stool samples for bacteria and chemical byproducts.
What it can’t tell you
- This trial only included healthy adults with mild constipation.
- The results might not apply to people with other digestive conditions or different health backgrounds.
- The study measured stool chemicals that evaporate easily, so changes in other types of chemicals might have been missed.
Who paid
- Funding
- Funded by Medical Research Council (from the PubMed record).
- Conflicts
- Competing interests: MS and ST are employees of BENEO/Südzucker Group. The authors alone are responsible for the content and writing of this article.
- Authors work at
- KU Leuven - University of Leuven, Belgium; Center for Microbiology, Belgium; Vrije Universiteit Brussel, Belgium
The paper
- Title
- Prebiotic inulin-type fructans induce specific changes in the human gut microbiota
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Vandeputte D, Falony G, Vieira-Silva S, et al (2017). Prebiotic inulin-type fructans induce specific changes in the human gut microbiota. Gut. doi:10.1136/gutjnl-2016-313271Free full textPubMed 28213610DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error