Dietary fiber is important for gut health more than probiotic supplements, new study shows.
A new study from the University of Texas MD Anderson Cancer Center says that cancer patients who said they ate more fiber-rich foods when they started immunotherapy treatment lived longer without their cancer growing than patients who didn’t eat enough fiber-rich foods or took probiotic supplements with low fiber foods.
Patients who did not use probiotic supplements saw the greatest effect. Preclinical experiments that were conducted concurrently with the observational data backed up the observational findings.
“Research from our team and others has shown that gut microbes impact response to immunotherapy treatment, but the role of diet and probiotic supplements has not been well studied,” according to the study authors.
“Our study sheds light on the potential effects of a patient’s diet and supplement use when starting treatment with immune checkpoint blockade. These results provide further support for clinical trials to modulate the microbiome with the goal of improving cancer outcomes using dietary and other strategies.”
The researchers started by looking at the gut microbiota profiles of 438 melanoma patients, 321 of whom had advanced cancer and were treated with systemic therapy, and 293 of whom exhibited a discernible response to treatment over time.
Immune checkpoint blockade, most often PD-1 inhibitors, was given to the vast majority of these patients (87 percent). A total of 158 patients took part in a lifestyle assessment about antibiotics and probiotic use, with 128 of them completing a food questionnaire before starting immune checkpoint therapy.
Patients who said they ate more fruits, vegetables, legumes, and whole grains met the study’s fiber consumption requirement.
In comparison to the 91 patients with insufficient fiber intake (median 13 months), the 37 patients with sufficient fiber intake had a better progression-free survival (median not attained).
A 30 percent lower risk of cancer progression or death was linked to every 5-grams of daily fiber intake.
When the patients were further divided into groups based on their fiber intake and use of commercially available probiotic supplements, response to immunotherapy was seen in 18 of 22 patients (82%) who reported both sufficient fiber intake and no probiotic use, compared to 60 of 101 patients (59%) who reported either insufficient fiber intake or probiotic use.
Response was defined as a complete or partial reduction of the tumor or a six-month period of disease stability. The use of probiotic was not linked to a meaningful difference in progression-free survival or the likelihood of responding to immunotherapy.
“Dietary fiber is important for gut health, just as it’s important for overall health, and the two things are very tightly intertwined,” added the study authors.
“In this study, we saw that dietary fiber also may be important to cancer treatment.”
In contrast to earlier findings, the overall diversity of gut flora was not linked to immunotherapy response, possibly due to the larger patient group.
To shed light on the probable processes behind the observational findings from the patient cohorts, the researchers also examined higher versus lower fiber diets and probiotic use in numerous preclinical melanoma models.
Probiotic use was linked to a decreased response to immune checkpoint inhibition, bigger tumors, poorer gut microbiome diversity, and less cytotoxic T cells in the tumor microenvironment in various models.
In preclinical models treated with PD-1 inhibitors, a high-fiber diet was linked to slower tumor growth and a much higher frequency of CD4+ T cells.
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