Walnuts and Colon Health

Study Purpose

The purpose of this research study is to examine whether adding walnuts to your diet can have a beneficial effect on the gut bacteria population, inflammatory markers in the blood, and the tissue that lines the inside of the colon.

Recruitment Criteria

Accepts Healthy Volunteers

Healthy volunteers are participants who do not have a disease or condition, or related conditions or symptoms

Study Type

An interventional clinical study is where participants are assigned to receive one or more interventions (or no intervention) so that researchers can evaluate the effects of the interventions on biomedical or health-related outcomes.

An observational clinical study is where participants identified as belonging to study groups are assessed for biomedical or health outcomes.

Searching Both is inclusive of interventional and observational studies.

Eligible Ages 40 Years - 75 Years
Gender All
More Inclusion & Exclusion Criteria

Inclusion Criteria:

  • - Individuals in one of the following groups: - Men and women between the ages of 40 to 75 years old, who are scheduled to undergo a routine screening or surveillance colonoscopy for colorectal cancer (CRC) and have a family history of CRC in a first degree relative diagnosed with CRC under the age of 65 years, or.
  • - Men and women between the ages of 45 to 75 years old, who are referred for colonoscopy following a positive fecal immunochemical test (FIT) and have not had a high quality colonoscopy in the past 3 years, or.
  • - Men and women between the ages of 45 to 75 years old, who have a personal history of colon polyps and are scheduled to undergo a surveillance colonoscopy.
  • - Willing and able to provide written informed consent for study participation.
  • - Willing to consume 2 ounces of walnuts daily for 3 weeks.
  • - Willing to avoid intake of ellagic acid/ellagitannin-rich foods (e.g., pomegranates, hazelnuts, pistachios, strawberries, raspberries, blackberries, oak-aged wines, and other food on a list given by researchers) and fermented dairy products containing viable Bifidobacteria or Lactobacilli) - Willing to stop taking dietary supplements, including probiotics.
  • - Willing to have 2 separate blood draws, as well as urine and stool collections.
  • - Willing to comply with all study requirements.

Exclusion Criteria:

  • - Individual has a personal history of CRC, or a history of any malignancy (other than skin cancer) within the past 5 years.
  • - Individual meets the Amsterdam criteria for Lynch Syndrome or has a history of familial adenomatous polyposis (FAP) - Individual has been treated with immunosuppressive agents or systemic steroids, excluding inhalers, at least two weeks prior to the Screening Visit and for the duration of the study.
  • - Use of antibiotics at least one month prior to the Screening Visit and for the duration of the study.
  • - Patients with severe medical illness or those at high risk for anesthesia, as determined by good clinical practice.
  • - Current evidence or previous history of ulcerative colitis or Crohn's disease.
  • - Colonoscopy performed for reasons other than screening or surveillance for CRC.
  • - HIV infection, chronic viral hepatitis.
  • - Allergy to walnuts or hypersensitivity to tree nuts.
  • - Peri-menopausal women with any chance or plan of pregnancy.
  • - Individuals with blood coagulation disorders or on anti-coagulant therapy.
  • - Any other condition that, in the opinion of the PI, might interfere with study objectives.
- No race/ethnicity, language or gender exclusions for this study

Trial Details

Trial ID:

This trial id was obtained from ClinicalTrials.gov, a service of the U.S. National Institutes of Health, providing information on publicly and privately supported clinical studies of human participants with locations in all 50 States and in 196 countries.


Phase 1: Studies that emphasize safety and how the drug is metabolized and excreted in humans.

Phase 2: Studies that gather preliminary data on effectiveness (whether the drug works in people who have a certain disease or condition) and additional safety data.

Phase 3: Studies that gather more information about safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs.

Phase 4: Studies occurring after FDA has approved a drug for marketing, efficacy, or optimal use.

Lead Sponsor

The sponsor is the organization or person who oversees the clinical study and is responsible for analyzing the study data.

UConn Health
Principal Investigator

The person who is responsible for the scientific and technical direction of the entire clinical study.

Daniel W. Rosenberg, Ph.D.
Principal Investigator Affiliation UConn Health
Agency Class

Category of organization(s) involved as sponsor (and collaborator) supporting the trial.

Other, NIH
Overall Status Recruiting
Countries United States

The disease, disorder, syndrome, illness, or injury that is being studied.

Colorectal Cancer, Diet Habit
Additional Details

This is a 29-day dietary intervention study where participants will be asked to consume 2 ounces of walnuts daily for 21 days, and at the end of the study period they will come in for a routine colonoscopy. After being informed about the study and potential risks, participants giving written informed consent will first start a 7-day wash-out period where they will be asked to avoid foods high in ellagitannins for the duration of the study. In addition, participants will be asked to complete food and activity questionnaires, a walnut consumption log, and two sets of 3-day dietary records during their participation in the study. Participants will also be asked to provide three urine samples, two blood samples, and two stool samples at multiple time points, and 8-10 colon tissue specimens (biopsies) will be collected during their colonoscopy procedure for the purposes of this study.

Arms & Interventions


Experimental: Walnut Consumption

Following enrollment, participants will start a 7-day wash-out period where they will be asked to avoid foods and beverages high in ellagitannins. These include pomegranates, hazelnuts, pistachios, walnuts (besides the samples given by the researchers), strawberries, raspberries, blackberries, oak-aged wines and spirits; a full list of foods and beverages to avoid will be provided. Then, participants will consume 2 ounces of walnuts daily with their usual diet while continuing to avoid ellagitannins for 21 days prior to their routine colonoscopy.


Other: - Walnuts

Participants consume 2 ounces of walnuts daily for 21 days

Contact a Trial Team

If you are interested in learning more about this trial, find the trial site nearest to your location and contact the site coordinator via email or phone. We also strongly recommend that you consult with your healthcare provider about the trials that may interest you and refer to our terms of service below.

UConn Health, Farmington, Connecticut




UConn Health

Farmington, Connecticut, 06032

Site Contact

Nuoxi Fan



Weill Cornell Medicine, New York, New York




Weill Cornell Medicine

New York, New York, 10065

Site Contact

Kevin Yeung