Fiber supplements may alter gut bacteria linked to colon cancer risk
NCT ID NCT05643859
First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This trial is testing whether taking daily fiber supplements can change the types and amounts of bacteria living in the colon. The study involves 120 adults with benign anal or colorectal conditions who are not currently on fiber supplements. Researchers will compare gut bacteria samples before and after fiber supplementation to see if the microbiome shifts in a way that might help prevent precancerous polyps.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- dietary fiber supplement
- What this could lead to
- If successful, this study could point toward a simple dietary strategy to reduce colon polyp risk.
- What could go wrong
- This is an early observational study, not a treatment trial. It only measures microbiome changes, not actual polyp prevention, so results may not lead to direct health benefits.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Not a phased trial
Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.
- Participants
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About 120 people
The number the study aims to enrol. It can still change while the study runs.
- Started
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Apr 2023
- Expected to finish
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Dec 2026
An estimate. End dates often move.
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 years and older
- Sex
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Anyone
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
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
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Get notified about this study
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
How to take part
Only the study team decides who joins. These are the ways to reach them.
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The places running it
1 site. The list below names each one and where it is.
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The official record
ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.
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A doctor treating you
A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.
Contacts and locations
Locations
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OHSU Knight Cancer Institute
RECRUITINGPortland, Oregon, 97239, United States