If the gut microbiome shapes how patients respond to cancer immunotherapy, then diet — the single biggest lever on the microbiome — should matter too. In December 2021, a study in Science from a team at MD Anderson, the NCI and Harvard put numbers on it.

Among 128 advanced-melanoma patients on immune checkpoint blockade, those reporting sufficient dietary fiber (at least ~20 g/day) had markedly better progression-free survival: median survival was not reached, versus 13 months for those eating less. Every additional 5 g of daily fiber was associated with a 30% lower risk of progression or death.

The probiotic wrinkle

The most provocative finding was an interaction. Patients who reported both sufficient fiber and no use of over-the-counter probiotic supplements did best of all — an 82% response rate versus 59%.

More fiber, fewer indiscriminate probiotics. The microbiome rewards feeding what’s already there over flooding it with strangers.

Caveats matter here: this is observational data from a single cohort, the upper confidence bound sat right at the edge of significance, and probiotic use on its own wasn’t statistically significant. It’s a strong association, not a prescription. But it lands on a consistent theme: a generic, high-dose probiotic is not automatically “more health.”

Sources

  1. Spencer et al., “Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response,” Science (Dec 23, 2021)
Editorial content for general information only — not medical advice, diagnosis or treatment. Talk to a qualified clinician about your own health.