Dietary fibre and the gut microbiome for immunotherapy response
Patients who eat plenty of fibre and avoid probiotic pills seem to respond better to immunotherapy for melanoma, probably because fibre feeds the right gut bacteria. A proper trial is under way.
In 128 melanoma patients on checkpoint inhibitors (Spencer et al., Science 2021), each 5 g/day of dietary fibre was associated with a 30% lower risk of progression or death, and the combination of sufficient fibre (at least 20 g/day) with no probiotic use had the best outcomes; in mice, low fibre or probiotics impaired the anti-PD-1 response. Gut taxa such as Faecalibacterium, Ruminococcaceae and Akkermansia repeatedly associate with response across cohorts, though the specific species differ by study and geography. This is observational in humans and confounded by overall health, so a fibre-intervention trial is the right next step; a randomised high-fibre diet trial in melanoma patients starting immunotherapy is recruiting at MD Anderson. The pragmatic message that is defensible today: eat more fibre, do not take over-the-counter probiotics, and avoid unnecessary antibiotics around immunotherapy.
How it works
Fermentable fibre yields short-chain fatty acids and sustains bacterial taxa that enhance dendritic-cell antigen presentation and systemic interferon tone, increasing CD8 T-cell infiltration into tumours.
- Consistent microbiome-response associations across independent cohorts
- Fibre is safe and cheap
- Mechanistic mouse data support causality
- Human data observational and mostly in melanoma
- Taxa vary between cohorts; no validated microbiome test
- Diet recall is noisy
Latest papers
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