Fiber may boost efficacy of fecal microbiota transplants for ulcerative colitis

Giorgia Guglielmi

28.07.2025

Fiber can influence how well bacteria from a fecal microbiota transplant successfully settle and grow in a person’s gut.

What is already known

Ulcerative colitis is a long-term colon disease that’s linked to an unhealthy gut microbiota. To treat it, scientists are exploring fecal microbiota transplantation, which has shown promise, but results vary due to factors such as donor differences, recipient characteristics, and how the treatment is given. Previous research has shown that diet, especially fiber, can help improve gut health and reduce inflammation. However, it’s unclear whether combining fecal microbiota transplantation with dietary changes could boost its efficacy.

What this research adds

Researchers investigated how psyllium, a dietary fiber, influences the success of fecal microbiota transplantation in people with ulcerative colitis. Fiber boosted the engraftment of beneficial donor bacteria, especially in people who initially did not respond well to fecal microbiota transplantation alone. Fiber also promoted certain microbial pathways related to sugar metabolism and increased the levels of helpful bacterial species.

Conclusions

Although the study couldn’t fully assess clinical outcomes, the findings show that fiber can influence how well bacteria from a fecal microbiota transplant successfully settle and grow in a person’s gut.

Ulcerative colitis is a chronic colon disease that’s hard to treat, as many people don’t respond well to treatment approaches such as fecal microbiota transplantation. Now, a new study found that dietary fiber can help beneficial bacteria from fecal transplants successfully take hold in the gut.

The findings, published in Med, suggest that fiber may improve outcomes for people with ulcerative colitis. The condition has been linked to an unhealthy gut microbiota, and while fecal microbiota transplantation has shown promise in treating it, results vary due to factors such as donor differences, recipient characteristics, and how the treatment is given.

Previous research has shown that diet, especially fiber, can help improve gut health and reduce inflammation. However, it’s unclear whether combining fecal microbiota transplantation with dietary changes could boost its efficacy.

Lasha Gogokhia at Weill Cornell Medicine in New York, USA and his colleagues set out to investigate this further in 27 people with mild to moderate ulcerative colitis.

Beneficial changes

The study participants were divided into three groups: people who received only a fecal microbiota transplant, people who received a fecal microbiota transplant and psyllium fiber, and a placebo group, some of whom also received fiber.

Three different donors were used, and one donor led to better clinical outcomes and greater, longer-lasting changes in recipients’ gut bacteria. The microbiota of this donor was more diverse and contained more beneficial bacteria associated with reduced inflammation than the microbiota of the other two donors.

Compared to people in the placebo group, those who received a fecal microbiota transplantation alone showed better clinical responses and changes in gut bacteria. These changes lasted for up to 12 weeks, and no serious side effects were reported.

Boosting engraftment

Certain beneficial gut bacteria, such as Bacteroides stercoris, were found more often in responders, suggesting a link between shifts in the gut microbiota and treatment success.

Although combining fecal microbiota transplantation with fiber didn’t show a clear added benefit, people who received fiber had increased levels of certain helpful bacteria. Many of these microbes stayed in the recipients’ guts long-term, the researchers found. Fiber also boosted the engraftment of beneficial donor bacteria, especially in people who initially did not respond well to fecal microbiota transplantation alone.

Although the study ended early and couldn’t fully prove the benefits of dietary fiber on ulcerative colitis, the findings support the idea that both having the right beneficial bacteria strains in the donor sample and successfully establishing those strains in the recipients are key to better outcomes, the authors say.