Scientists are now studying if fiber can help cancer treatments be more effective. It turns out that some cancer patients respond to immunotherapy, and some don’t. Scientists have found that patients who harbor certain gut bacteria have better responses to immunotherapy than patients who lack them. Some of the gut microbes that appear to improve how patients respond to immunotherapy are known to thrive on fiber. Their findings, published in Science in December, showed that every five-gram increase in daily fiber intake was associated with a 30% lower risk of death or cancer progression.