A surprising study suggests that what gut microbes eat may influence how well cancer immunotherapy works—but the finding is from mice, not a dietary recommendation for people. Researchers at McGill University tested 12 diets and found that diet and gut bacteria could work together to affect responses to immune checkpoint inhibitors, a widely used class of cancer treatments.
What did the researchers find?
In mouse models, some diets associated with weight gain were linked to stronger responses to immunotherapy. The results suggest that body weight alone may not explain the effects: the interaction between diet and the gut microbiome—the community of microorganisms living in the digestive tract—also mattered. In experiments, the researchers found that particular gut bacteria, including Lactobacillus johnsonii, could cooperate with diet to support anti-tumour responses.
Why this discovery is unexpected
It challenges a simple assumption that diet affects cancer treatment only through body weight or general health. The findings point instead to a more specific question: could food components shape gut microbes and their metabolites in ways that influence immune activity? The study offers a research lead for understanding why some patients respond differently to immune checkpoint blockade.
Important: this is not advice to eat an unhealthy diet
The results do not show that a high-fat or weight-promoting diet treats cancer, improves immunotherapy in people, or should be adopted by patients. The experiments were conducted in mice, and diet-related health risks remain. The researchers say further work is needed to identify the mechanisms and determine whether safer, targeted approaches could be developed for human care. Anyone receiving cancer treatment should discuss nutrition changes with their oncology team.
Research paper: Desharnais et al., “Diet–microbiome synergy underlies obesity-associated immunotherapy efficacy,” Nature. Read the paper. Research context: McGill University’s summary.
