# Test a high-fibre diet as an immunotherapy adjunct

Source: https://onco.cc/ideas/idea-bio2-fibre-diet-io-trial/  
OnCo record `idea-bio2-fibre-diet-io-trial` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

People who eat more fibre appear to respond better to immunotherapy, while some probiotic supplements may do the opposite. A proper trial would settle it.

## Summary

Observational data in melanoma associate higher dietary fibre intake with improved checkpoint response, and over-the-counter probiotic use with worse response, with supporting mouse experiments. Diet is a cheap, scalable and modifiable exposure but has never been tested randomly alongside checkpoint therapy with microbiome and immune endpoints. Adherence measurement, through stool short-chain fatty acids, makes a rigorous trial possible.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: A supervised high-fibre dietary intervention during checkpoint therapy improves response rate compared with usual diet, with stool short-chain fatty acid levels mediating the effect.
- Rationale: Fibre fermentation produces short-chain fatty acids that alter T-cell differentiation, giving a plausible mechanism, and the observational effect size reported in melanoma was large. The intervention has no toxicity and independent health benefits.
- Proposed test: A randomised trial of provided high-fibre meals versus usual diet in patients starting checkpoint blockade, with objective response as primary endpoint and stool metabolomics and metagenomics as mechanistic endpoints.
- Maturity: early-clinical
- Actor: research

## Sources

- Bottleneck evidence (No one can predict who responds to immunotherapy): Haslam & Prasad (JAMA Network Open 2019): https://doi.org/10.1001/jamanetworkopen.2019.2535

## Connected records

- cancers: [Melanoma](https://onco.cc/cancers/melanoma/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/)
- technologies: [Dietary fibre and the gut microbiome for immunotherapy response](https://onco.cc/technologies/dietary-fibre-microbiome-io/), [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/)
- institutions: [MD Anderson Cancer Center](https://onco.cc/institutions/md-anderson/)
- people: [Laurence Zitvogel](https://onco.cc/people/laurence-zitvogel/)
- bottlenecks: [Cold tumours and the immunosuppressive microenvironment](https://onco.cc/bottlenecks/b-tme-immunosuppression/), [No incentive to repurpose cheap drugs](https://onco.cc/bottlenecks/b-generic-repurposing/), [No one can predict who responds to immunotherapy](https://onco.cc/bottlenecks/b-immunotherapy-response/)
- key papers: [Estimation of the Percentage of US Patients With Cancer Who Are Eligible for and Respond to Checkpoint Inhibitor Immunotherapy Drugs](https://onco.cc/key-papers/paper-haslam-jama-netw-open/)
- ideas: [Capture diet, fibre and antibiotic exposure in every immunotherapy pivotal trial](https://onco.cc/ideas/idea-nl-diet-covariates-io-trials/)

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