To the surprise of researchers, certain diets often considered "unhealthy" or "fattening" were associated with better responses to a type of cancer immunotherapy.
"There is a synergistic relationship between the bacteria that reside in our GI tract, and the food we eat," said Daniela Quail , Associate Professor in the Department of Physiology and Principal Investigator at the Rosalind & Morris Goodman Cancer Institute.
"Even with the right composition of bacteria in your gut, the foods you eat to nourish those populations can determine whether or not you respond to treatment," said Quail, who co-led a team investigating how diet could affect the success of immune checkpoint inhibitors, a common form of immunotherapy. Other senior members of their team included McGill researcher Logan Walsh, and CR-CHUM collaborators Bertrand Routy and Arielle Elkrief. Their research was published in Nature.
"Our findings were surprising because they highlighted a benefit of some obesogenic diets," she said. "That tells us the relationship between diet and cancer treatment is more complex than a simple message to eat healthy and exercise."
The findings do not mean people with cancer should adopt diets associated with weight gain, which carries well-known health risks. Instead, researchers hope to find out what is driving the effect on the gut microbiome, the trillions of bacteria that live in the digestive tract, and harness it to improve treatment.
New insights into 'obesity paradox'
The study was inspired by a puzzling phenomenon known more broadly as the "obesity paradox." While obesity is generally associated with higher cancer incidence and mortality, several studies have shown that cancer patients with a higher body mass index (BMI) often respond better to immune checkpoint inhibitors.
By testing 12 different diets in mice, researchers found that some diets associated with obesity improved immunotherapy responses, even after shorter exposure times.
The findings help explain an emerging mystery in cancer research, suggesting the link between obesity and immunotherapy may have less to do with body weight than previously thought and more to do with how diet and gut bacteria synergize to influence the immune system.
About the study
" Diet–microbiome synergy underlies obesity-associated immunotherapy efficacy" by McGill PhD graduate Lysanne Desharnais and Daniela Quail et al., was published in Nature. Funding was provided by the Canadian Institutes of Health Research, the Canadian Cancer Society, the Terry Fox Research Institute, the Canada Foundation for Innovation and philanthropic partners including La Vie en Rose and the Bachynski Family Foundation.
