Researchers at MD Anderson Cancer Center studied melanoma patients being treated with immune checkpoint inhibitors, tracking their diets and any probiotic use alongside stool samples of their gut bacteria, then tested the same variables directly in mice to confirm cause and effect.
Among 128 melanoma patients on checkpoint inhibitors, those reporting sufficient dietary fiber had significantly longer progression-free survival, and the benefit was clearest in those who also took no probiotic supplements. Mice fed a low-fiber diet or given probiotics responded worse to treatment, with fewer cancer-fighting T cells inside their tumors.
The probiotic result ran against a common assumption that supplement-bottle bacteria help the immune system; in the mice, popular probiotics weakened the response to treatment. The work was observational in patients and causal only in mice, so a clinical trial of dietary fiber in cancer patients is the next step before doctors recommend it.
Read the original study
Spencer et al., Science, 2021 · doi.org/10.1126/science.aaz7015
Fiber helped; the probiotic pill did not.
Source
- Spencer, C. N., McQuade, J. L., Gopalakrishnan, V., McCulloch, J. A., Vetizou, M., Cogdill, A. P., Khan, M. A. W., Zhang, X., White, M. G., Peterson, C. B., Wong, M. C., Morad, G., Rodgers, T., Badger, J. H., Helmink, B. A., Andrews, M. C., Rodrigues, R. R., Morgun, A., Kim, Y. S., . . . Wargo, J. A. (2021). Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response. Science, 374(6575), 1632–1640. https://doi.org/10.1126/science.aaz7015