Inulin fibre, bile acids and type 2 inflammation in mice
What it found
In mice, an inulin fibre diet changed gut bacteria and raised levels of bile acids, which triggered type 2 inflammation in the gut and lungs.
The same effects occurred in mice given human gut bacteria, and cholic acid copied the effect.
What they found
Animal and lab studies
Gut bacteria changes
In mice, inulin increased Bacteroidetes and decreased Firmicutes in the faeces. Some of these bacteria are also found in the human gut.
Bile acids in blood
Inulin raised levels of several bile acids in the blood, especially cholic acid. Faecal levels of some bile acids dropped, suggesting they were reabsorbed.
Type 2 inflammation
Mice on inulin had more eosinophils in the colon and lungs, starting within one week and lasting over two months. This required gut bacteria, as germ-free mice did not show it.
Human gut bacteria
Mice given human gut bacteria also showed raised bile acids and type 2 inflammation after inulin, showing the effect is not limited to mouse bacteria.
Allergy and infection
In mice exposed to allergens or infected with a parasite, inulin made type 2 inflammation worse but also helped clear the parasite faster, in an eosinophil-dependent way.
Studies in people and animals
Cholic acid mimics effect
Giving mice cholic acid copied the inulin effect, raising eosinophils and IL-5-producing ILC2 cells. Cholic acid also increased these cells in human blood cells in the lab.
What the authors conclude
“Taken together, these data reveal that dietary inulin fibre triggers microbiota-derived cholic acid and type 2 inflammation at barrier surfaces with implications for understanding the pathophysiology of allergic inflammation, tissue protection and host defence.”
Also in their conclusions
- They conclude that dietary inulin fibre triggers microbiota-derived cholic acid and type 2 inflammation at barrier surfaces.
- They propose that the immune outcome of eating inulin depends on the balance between different microbiota-derived metabolites and immune pathways.
- They suggest this could provide insights into barrier immunity during infection, allergic inflammation and tissue protection.
How it was done
The authors wanted to understand how dietary fibres and the metabolites made by gut bacteria affect the immune system, because most of these effects are not well defined.
They fed mice a diet with 30% fibre (26% inulin and 4% cellulose) or a control diet for 2 weeks, then measured gut bacteria, metabolites in blood and faeces, and immune cells. They also tested mice with human gut bacteria, mice lacking certain immune cells or receptors, and mice infected with a parasite or exposed to allergens.
What it can’t tell you
- These are mostly animal studies. They cannot show what happens in people.
- The human cells were tested in the lab, not in the body, so the full effect in people is not known.
- The study used a specific high-fibre diet, so results may not apply to other amounts or types of inulin.
Who paid
- Funding
- Funded by NIAID NIH HHS; NIAMS NIH HHS; NICHD NIH HHS; Howard Hughes Medical Institute; NIDDK NIH HHS; NCATS NIH HHS; NIGMS NIH HHS; NHLBI NIH HHS (from the PubMed record).
- Conflicts
- Competing interests D.A. has contributed to scientific advisory boards at Pfizer, Takeda, FARE and the KRF. F.C.S. is a cofounder of Ascribe Bioscience and Holoclara. The other authors declare no competing interests.
- Authors work at
- Cornell University, USA
The paper
- Title
- Inulin fibre promotes microbiota-derived bile acids and type 2 inflammation
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Arifuzzaman M, Won TH, Li TT, et al (2022). Inulin fibre promotes microbiota-derived bile acids and type 2 inflammation. Nature. doi:10.1038/s41586-022-05380-yFree full textPubMed 36323778DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error