24-Hour Fast Boosts Gut Microbe That Helps Repair Radiation Damage

Fasting for 24 hours increased the amount of a gut bacterium called Akkermansia muciniphila in the small intestine, and that microbe helped the intestinal lining regrow after radiation damage, according to preclinical research from The University of Texas MD Anderson Cancer Center published in the Proceedings of the National Academy of Sciences.

The work has not been tested in people. Its authors hope it could one day point to ways of protecting healthy tissue during abdominal radiation therapy, possibly without asking patients to stop eating.

Why the gut suffers during radiation

Radiation is used against cancers in the abdomen, including pancreatic, colorectal and gynecologic cancers. It kills tumor cells but can also hurt healthy tissue nearby. The small intestine is especially exposed because its thin inner lining is very sensitive to radiation.

When that lining is damaged, patients can develop nausea, diarrhea and infections, and severe injury can be life threatening. The risk can also limit how much radiation doctors are able to give. Earlier preclinical work from the lab of Helen Piwnica-Worms had shown that fasting before radiation helped the intestine recover, but the reason was not known.

How a 24-hour fast prepares intestinal cells

The new study traces a chain of steps. During the fast, Akkermansia muciniphila (AKK for short) became more abundant in the small intestine. The bacterium makes a compound called propionate. Propionate, together with other metabolic shifts caused by fasting, changes histones, the proteins that DNA wraps around inside cells.

Small chemical tags on histones can switch genes on or off without altering the DNA code itself. Here, the changes opened up stretches of DNA that hold genes for tissue regeneration. A group of intestinal cells carrying these repair programs grew in number during the fast. After radiation, those primed cells expanded and helped rebuild the damaged lining.

Piwnica-Worms, a professor of Experimental Radiation Oncology who co-led the study with Kunal Rai, a professor of Genomic Medicine, compared the effect to giving cells “an emergency preparedness plan.”

Testing whether the microbe was needed

To check AKK’s role, the researchers removed the bacterium. Without it, fasting no longer gave the same regenerative benefit. The protection came back only when the bacterium was restored and the fast was repeated, which showed that neither fasting nor the microbe alone produced the full effect.

What it means for cancer treatment

The results link diet, gut bacteria and changes in how intestinal cells read their genes before an injury happens. If the same pathway works in humans, it could offer a way to help healthy tissue recover from radiation. The team is also interested in other fast-dividing tissues that cancer treatment can harm, such as bone marrow.

Because fasting is hard for many cancer patients, the researchers are looking at alternatives that might trigger the same repair process, such as giving the beneficial bacteria or the molecules they produce. Rai said fasting “is not always practical for cancer patients,” and that diet, targeted microbes or their metabolites are all possible routes.

What is still unknown

The study is preclinical, and the published summary does not report results in people. More research is needed to find out whether the mechanism operates in humans and whether using it would be safe and improve outcomes for patients receiving radiation. Only after that could clinical trials test the approach in people undergoing abdominal radiation. None of this work is a recommendation for patients to fast before treatment.

The research was funded by the National Cancer Institute, part of the National Institutes of Health, and the Cancer Prevention and Research Institute of Texas. The paper, by Praveen Barrodia and colleagues, appears in the Proceedings of the National Academy of Sciences, 2026, volume 123, issue 26. DOI: 10.1073/pnas.2529215123.

Source: ScienceDaily