Effects of fiber supplements on gut bacteria in the colon

Changes in Colonic Microbiome With Fiber Supplementation

Not applicable Interventional OHSU Knight Cancer Institute · NCT05643859

This study is testing if taking daily fiber supplements can change the gut bacteria in the colon to help prevent precancerous polyps.

Quick facts

PhaseNot applicable
Study typeInterventional
Enrollment120 (estimated)
Ages18 Years and up
SexAll
SponsorOHSU Knight Cancer Institute Academic / other
Locations1 site (Portland, Oregon)
Trial IDNCT05643859 on ClinicalTrials.gov

What this trial studies

This clinical trial investigates how daily fiber supplementation influences the microbiome of the colonic mucosa over a 28-day period. Participants will take dietary fiber orally and may undergo standard procedures like proctoscopy or colonoscopy for assessment. The primary goal is to determine the impact of dietary fiber on the gut microbiome, which is crucial for preventing the development of precancerous polyps. Blood samples will also be collected for further analysis.

Who should consider this trial

Good fit: Ideal candidates include adults aged 18 and older with benign anorectal conditions who are undergoing standard colonoscopy procedures.

Not a fit: Patients with active malignancies, inflammatory bowel diseases, or hereditary colon cancer syndromes will not benefit from this study.

Why it matters

Potential benefit: If successful, this study could help in preventing the formation of precancerous polyps in patients at risk.

How similar studies have performed: Other studies have shown promising results in modifying the gut microbiome through dietary interventions, suggesting potential success for this approach.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Age \>= 18 years
* Ability to understand and the willingness to sign a written informed consent document
* Patients who present with a chief complaint of a benign anorectal pathology including hemorrhoids, anal fissures, and anal fistulas without underlying conditions such as colorectal cancer or Crohn's disease or are undergoing a standard of care colonoscopy procedure

Exclusion Criteria:

* Patients with an active malignancy, Crohn's disease, ulcerative colitis, and immunosuppressed patients
* Patients with hereditary colon cancer syndrome including Lynch syndrome or Familial Adenomatous Polyposis (FAP)
* Patients with a prior history of total or partial colon resection
* Colorectal pathology, such cancer or proctitis, after initial study scope

Where this trial is running

Portland, Oregon

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Benign Colorectal NeoplasmNon-Neoplastic Anal Disorder
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.