produce short-chain fatty acids with anti-inflammatory, anti-tumor activity.
Past research has suggested that the gut microbiome can influence cancer patients’ responses to immune checkpoint inhibitors. Those drugs, such as Keytruda and Opdivo, are used to treat several types of cancer, and work by releasing a particular “brake” on immune system T-cells, freeing them to find and attack cancer cells.
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Can a high-fiber diet help cancer patients?
So an intriguing question is whether diet, including fiber, can alter patients’ responses to those treatments, study author Dr. Jennifer Wargo, of the University of Texas MD Anderson Cancer Center in Houston says.
To investigate, her team studied 128 patients with advanced melanoma, the deadliest form of skin cancer.
Diet questionnaires showed that 37 of those patients had “sufficient” fiber intake — at least 20 grams per day from foods like vegetables, fruit, beans and whole grains. The rest were getting too little dietary fiber.
On average, the study found, patients eating enough fiber fared better: 76% responded to immunotherapy, versus 60% of those with low-fiber diets. That meant their tumors had at least partly regressed, or their cancer remained stable for at least six months.
No such benefit was found among the 49 patients who said they used probiotic supplements, however. And the best response rate was seen among patients who ate plenty of fiber but took no probiotics — at 82%.
None of that proves fiber was the reason.
So the researchers next studied lab mice with melanoma tumors. They found that giving the animals commercially available probiotic supplements interfered with their response to immune checkpoint inhibitors.
In contrast, a high-fiber diet slowed tumor growth in mice treated with the drugs, and appeared to boost