Immunotherapy Response Depends on Healthy Gut Bacteria – and Whole Grains!


One of the most striking discoveries in recent years revealed that “friendly” bacteria living in your digestive system — your gut microbiome — are actually crucial in helping immunotherapy drugs work for cancer patients. Immunotherapies represent a major advance in cancer treatment, firing up sluggish or suppressed immune systems to kill cancer cells in ways that other therapies have not succeeded. Kidney cancer, melanoma and lung cancer are just a few of the lethal cancers that immunotherapy has on the run, with astonishing stories of disease remissions appearing in scientific literature and responsible internet reports.

But one of the bewildering problems with immunotherapy is why not all patients experience these astounding remissions. For instance, the immunotherapy drug Keytruda cuts mortality risks in half for lung cancer patients. That’s terrific for those patients whose disease “disappears.” But what about the other patients who are failed by the drug? Why don’t they gain the same excellent response from the same drug?

Doctors first suspected that the microbiome might be involved. They observed that patients who received antibiotics when starting immunotherapies were much less likely to have remissions than those not given antibiotics. Antibiotics are known to kill the friendly bacteria of the microbiome (not just kill the pathogens), and it had been established that the microbiome worked together with the immune system. So researchers started analyzing more precisely the characteristics of patients’ microbiomes who did versus those who did not respond to immunotherapy.
Soon multiple research groups published papers noting that people whose microbiomes were composed of many bacterial species (”high species diversity”) — associated with a healthy digestive system — did better with immunotherapy. This ushered in a new field of research, exploring ways to improve the microbiome for cancer patients.
Of course, when we consider promoting friendly gut bacteria, our thoughts may automatically jump to probiotics — supplements given to patients after antibiotic treatments. But should immunotherapy patients start taking probiotics?

Probably not! A study presented this month at AACR (American Association of Cancer Research) cast doubt on using probiotics during immunotherapy. Researchers at MD Anderson had studied the influence of probiotics and diet in a group of melanoma patients getting immunotherapy. They took stool samples so they could identify which bacteria appeared in the microbiomes of patients who had good immunotherapy outcomes.

This study found that patients who took probiotics were 70% less likely to have good immunotherapy outcomes! Surprisingly, rather than improving the composition of the microbiome, probiotics were associated with significantly less species diversity, resulting in the poor response. This observational study, therefore, suggests caution in using probiotic supplements if you are receiving immunotherapy. It also indicates that probiotics alone will not solve microbiome problems in cancer patients.

But the MD Anderson team did discover certain dietary patterns that link to a substantial advantage in immunotherapy and the microbiome. Patients who ate high-fiber diets were over five times more likely to respond to immunotherapy than those who ate low fiber diets. And specific food patterns connected favorably to microbiome composition: For example, whole grains were linked to bacterial species associated with good immunotherapy response. On the other hand, diets with high levels of added sugars or processed meat had bacteria associated with poor response to immunotherapy.

Why do whole grains and fiber promote useful, beneficial bacteria? Our digestive system uses the fiber in certain foods we eat to help desirable bacteria grow. And simply, whole grains are one of the best sources of dietary fiber. Significantly, this high fiber intake can explain the healthy bacterial populations in the immunotherapy responders. BUT PLEASE NOTE: Sugar and processed meat (careful, all you bacon fans!) do not support healthy bacterial growth.

These days, whole grains have been attacked by a lot of criticism among some big-name diet writers. Yet based on solid, reliable science, we have always advised that whole grains – not refined grain products — are essential in a healthy diet for cancer patients. And this study reinforces their importance, especially for patients in treatment. These findings also boost our fundamental contention that supplements alone – probiotics in this case – do not by themselves represent a solo way to get healthy (though within a whole fully integrative system they definitely can help address specific lab findings showing clinical needs.)

A healthy diet designed for each individual that eliminates refined sugars and emphasizes plant foods including whole grains — as factors within a well-balanced, personalized nutrition plan — is what we recommend for each of our cancer patients. Our clinical staff members are prepared to help design with you and for you a full set of dietary and detailed lifestyle recommendations that support your process of enhancing genuine health.

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