Fecal microbiome transplant in food allergy: bile acid metabolites implicated in oral tolerance
Oral encapsulated FMT showed a preliminary signal of increased peanut reactivity threshold in a subset of allergic adults, with a mechanism linked to bile acid metabolites and RORγt+ Treg cells.
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What the study showed
In 15 peanut-allergic adults, 6 of 15 participants showed an increased reactivity threshold after FMT, with higher response rates in the antibiotic-pretreated group (3/5 vs 3/10). Responders displayed increased RORγt+ Treg cells and decreased TH2 cells. In murine models transplanted with microbiomes from human responders, protection was associated with greater Bacteroides colonization and increased bile acid metabolites.
How it was done
Phase 1 open-label, uncontrolled trial (NCT02960074) enrolling 15 peanut-allergic adults receiving oral encapsulated FMT, with or without antibiotic pretreatment. Mechanistic experiments were conducted in mouse models.
Risk of bias
A sample of 15 participants with no control group makes it impossible to distinguish FMT effect from natural variation or placebo effect. Open-label phase 1 design precludes efficacy inferences; mechanistic data derive primarily from animal models.
What this study does NOT prove
The study does not prove that FMT induces sustained tolerance to food allergy in humans or that bile acid manipulation is a viable therapeutic approach.
In clinical practice
Evidence is insufficient for any clinical recommendation; this study provides phase 1 safety data and an exploratory efficacy signal only. No change in clinical practice is justified based on this study alone.
Limitations
A sample of 15 participants with no control group makes it impossible to distinguish FMT effect from natural variation or placebo effect. Open-label phase 1 design precludes efficacy inferences; mechanistic data derive primarily from animal models.
Technical appendix
Version history
- 1.0 · 2026-08-06 — Auto-generated under Evidence Standard v1.0
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