Unhealthy diets boosted cancer immunotherapy in mice, study finds

Some diets considered unhealthy improved the effectiveness of a common cancer immunotherapy in mice, according to new research. The study indicates that treatment success may hinge on the foods that nourish gut bacteria, not just the bacteria themselves. "There is a synergistic relationship between the bacteria that reside in our GI tract, and the food we eat," said Daniela Quail, an associate professor at McGill University's Rosalind & Morris Goodman Cancer Institute. She noted that the right foods can determine whether a patient responds to treatment, even with optimal gut bacteria. Quail co-led the research, which was published in the journal Nature.

The findings revealed that some diets linked to weight gain appeared to make immunotherapy more effective. "Our findings were surprising because they highlighted a benefit of some obesogenic diets," Quail said. This challenges straightforward advice to simply eat healthy and exercise during cancer care. The researchers stress that the results do not mean cancer patients should adopt diets that promote obesity, as excess weight carries known health risks. The team instead aims to understand how different foods influence the gut microbiome.

The work addresses a known puzzle in cancer research called the "obesity paradox." While obesity increases cancer risk and mortality, some studies show heavier patients sometimes respond better to immune checkpoint inhibitors. To explore this, the team fed mice 12 different diets. They found that some obesogenic diets boosted the animals' responses to immunotherapy, even over short periods. This suggests the treatment advantage may not come from excess body weight itself. It may instead stem from how diet and gut bacteria together affect the immune system. By understanding these interactions, scientists hope to find ways to replicate the beneficial effects without the risks of obesity. The study was led by McGill PhD graduate Lysanne Desharnais and Quail, with collaborators from McGill and the CR-CHUM. Funding came from the Canadian Institutes of Health Research, the Canadian Cancer Society, the Terry Fox Research Institute, and several philanthropic foundations.

With files from Science Daily