Walnuts and Colon Health

Microbiota, Metabolites and Colon Neoplasia

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.

Study Overview

• Status: Completed
• Conditions: Colorectal Cancer; Diet Habit
• Intervention / Treatment: Other: Walnuts

Detailed Description

This is a 30-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.

• Study Type: Interventional
• Enrollment (Actual): 140
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Connecticut
    • Farmington, Connecticut, United States, 06032
      • UConn Health
  • New York
    • New York, New York, United States, 10065
      • Weill Cornell Medicine

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 40 years to 75 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Men and women between the ages of 39-75 years old who meet the criteria of one of the following groups and are eligible to undergo a routine screening or surveillance colonoscopy for colorectal cancer (CRC):

   1. Individuals who have a family history of colon polyps or CRC in a first-degree relative diagnosed with CRC under the age of 65 years, or
   2. Individuals who are referred for colonoscopy following a positive fecal immunochemical test (FIT) or a positive Cologuard screening test and have not had a high-quality colonoscopy in the past 3 years, or
   3. Individuals who have a personal history of colon polyps
2. Willing and able to provide written informed consent for study participation
3. Willing to consume 2 ounces (56 grams) of walnuts daily for 3 weeks
4. Willing to avoid intake of EA/ET-rich foods and beverages (e.g., pomegranates, hazelnuts, pistachios, strawberries, raspberries, blackberries, oak-aged wines, and other items on a list given by researchers) and fermented dairy products containing viable Bifidobacteria or Lactobacilli)
5. Willing to stop taking dietary supplements, including probiotics
6. Willing to have two separate blood draws, as well as urine and stool collections
7. Willingness to comply with all study requirements

Exclusion Criteria:

1. Individual has a personal history of CRC, or a history of any malignancy (other than skin cancer) within the past 5 years
2. Individual meets the Amsterdam criteria for Lynch Syndrome or has a history of familial adenomatous polyposis (FAP)
3. 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
4. Use of antibiotics at least one month prior to the Screening Visit and for the duration of the study
5. Patients with severe medical illness or those at high risk for anesthesia, as determined by good clinical practice
6. Current evidence or previous history of ulcerative colitis or Crohn's disease
7. Colonoscopy performed for reasons other than screening or surveillance for CRC
8. HIV infection, chronic viral hepatitis
9. Allergy to walnuts or hypersensitivity to tree nuts
10. Peri-menopausal women with any chance or plan of pregnancy
11. Individuals with blood coagulation disorders or on anti-coagulant therapy
12. Any other condition that, in the opinion of the PI, might interfere with study objectives
13. No race/ethnicity, language or gender exclusions for this study

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

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

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Bacterial composition and taxonomy changes in the fecal microbiome	Bacterial composition and taxonomy changes in the fecal microbiome will be assessed using 16 Svedberg unit (16S) ribosomal ribonucleic acid (rRNA) sequencing, at day 7 (post-washout/pre-walnut supplementation) and at day 28 (post-walnut supplementation).	Day 7 and Day 28
Bacterial diversity changes and strain-level variations in the fecal microbiome	Bacterial diversity/abundance changes and strain-level variations in the fecal microbiome will be assessed using metagenomic shotgun sequencing at day 7 (post-washout/pre-walnut supplementation) and at day 28 (post-walnut supplementation).	Day 7 and Day 28
Bacterial gene expression profile changes in the fecal microbiome	Bacterial gene expression profile changes in the fecal microbiome will be assessed using metagenomic ribonucleic acid (RNA) sequencing at day 7 (post-washout/pre-walnut supplementation) and at day 28 (post-walnut supplementation).	Day 7 and Day 28
Correlation of urolithin levels with fecal microbiome composition	Detailed statistical analyses will be used to correlate urolithin formation with the composition of the fecal microbiome at day 7 (post-washout/pre-walnut supplementation) and at day 28 (post-walnut supplementation).	Day 7 and Day 28
Urolithin levels in urine	Urolithin levels will be measured in urine by ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry at day 0 (baseline/pre-washout), day 7 (post-washout/pre-walnut supplementation) and day 30 (post-walnut supplementation/end of study).	Day 0, Day 7 and Day 30
Association of urolithin levels with presence (and type) of colonic lesions	Baseline urolithin levels measured in the urine by ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry will be associated with the presence (and type) of colonic lesions (e.g., advanced adenomas (AAs) or sessile serrated adenomas/polyps (SSA/Ps)) detected during the colonoscopy procedure at the end of the study (day 30).	Day 30
Correlation of colonic lesion gene expression with urolithin production	Colonic lesion (AAs and SSA/Ps) biopsies obtained at the end of the study (day 30) during the colonoscopy procedure will undergo DNA sequence-based analysis to determine gene expression profiling. These results will be compared to urinary urolithin levels measured at baseline to establish correlations between urolithin production and colorectal cancer risk markers.	Day 30
Association of urolithin levels with the immune composition of the tumor microenvironment	FFPE colon polyp tissue sections will be analyzed by the NCI Imaging Core (Frederick, MD) using imaging mass cytometry (IMC) to determine immune cell populations present within the tumor microenvironment. This data will be used to establish correlations with urolithin production.	Day 30

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Short-chain fatty acid composition in stool	Short-chain fatty acids in freeze-dried stool samples will be measured using differential mobility separation at day 7 (post-washout/pre-walnut supplementation) and at day 30 (post-walnut supplementation).	Day 7 and Day 30
Bile acid metabolism in stool	Primary and secondary bile acids in freeze-dried stool samples will be analyzed using standard liquid chromatography-mass spectrometry methods at day 7 (post-washout/pre-walnut supplementation) and at day 30 (post-walnut supplementation).	Day 7 and Day 30
Inflammatory markers in blood	Markers of systemic inflammation associated with adenoma risk will be measured in plasma using commercial enzyme-linked immunoassay (ELISA) kits at day 7 (post-washout/pre-walnut supplementation) and at day 30 (end of study).	Day 7 and Day 30
Correlation of dietary behavior with presence (or absence) of colonic polyps	Overall diet quality and habits documented on brief food questionnaires will be analyzed by NutritionQuest at day 7 (post-washout/pre-walnut supplementation). Dietary behavior data will be correlated with the presence or absence of colonic polyps detected during the colonoscopy procedure at the end of the study (day 30).	Day 7 and Day 30
Correlation of dietary behavior with fecal microbiome composition and diversity	Dietary behavior data documented on 3-day dietary records will be analyzed by Nutrition Data System for Research software. This data will be correlated with fecal microbiome composition and diversity at day 7 (post-washout/pre-walnut supplementation) and at day 30 (post-walnut supplementation).	Day 7 and Day 30
Correlation of dietary behavior with urolithin production	Dietary behavior data documented on 3-day dietary records will be analyzed by Nutrition Data System for Research software. This data will be correlated with urolithin levels at day 7 (post-washout/pre-walnut supplementation) and at day 30 (post-walnut supplementation).	Day 7 and Day 30

Collaborators and Investigators

• Sponsor: UConn Health
• Collaborators: National Cancer Institute (NCI); National Institutes of Health (NIH); University of Florida; Weill Medical College of Cornell University; University of Connecticut; California Walnut Commission; Spanish National Research Council
• Investigators: Principal Investigator: Daniel W. Rosenberg, Ph.D., UConn Health; Principal Investigator: Christian Jobin, Ph.D., University of Florida

Publications and helpful links

General Publications

• Nakanishi M, Matz A, Klemashevich C, Rosenberg DW. Dietary Walnut Supplementation Alters Mucosal Metabolite Profiles During DSS-Induced Colonic Ulceration. Nutrients. 2019 May 20;11(5):1118. doi: 10.3390/nu11051118.
• Chen Y, Nakanishi M, Bautista EJ, Qendro V, Sodergren E, Rosenberg DW, Weinstock GM. Colon Cancer Prevention with Walnuts: A Longitudinal Study in Mice from the Perspective of a Gut Enterotype-like Cluster. Cancer Prev Res (Phila). 2020 Jan;13(1):15-24. doi: 10.1158/1940-6207.CAPR-19-0273. Epub 2019 Dec 9.
• Nakanishi M, Chen Y, Qendro V, Miyamoto S, Weinstock E, Weinstock GM, Rosenberg DW. Effects of Walnut Consumption on Colon Carcinogenesis and Microbial Community Structure. Cancer Prev Res (Phila). 2016 Aug;9(8):692-703. doi: 10.1158/1940-6207.CAPR-16-0026. Epub 2016 May 23.
• Hong BY, Ideta T, Lemos BS, Igarashi Y, Tan Y, DiSiena M, Mo A, Birk JW, Forouhar F, Devers TJ, Weinstock GM, Rosenberg DW. Characterization of Mucosal Dysbiosis of Early Colonic Neoplasia. NPJ Precis Oncol. 2019 Nov 14;3:29. doi: 10.1038/s41698-019-0101-6. eCollection 2019.
• Tomas-Barberan FA, Gonzalez-Sarrias A, Garcia-Villalba R, Nunez-Sanchez MA, Selma MV, Garcia-Conesa MT, Espin JC. Urolithins, the rescue of "old" metabolites to understand a "new" concept: Metabotypes as a nexus among phenolic metabolism, microbiota dysbiosis, and host health status. Mol Nutr Food Res. 2017 Jan;61(1). doi: 10.1002/mnfr.201500901. Epub 2016 Jun 20.
• Fan N, Fusco JL, Rosenberg DW. Antioxidant and Anti-Inflammatory Properties of Walnut Constituents: Focus on Personalized Cancer Prevention and the Microbiome. Antioxidants (Basel). 2023 Apr 22;12(5):982. doi: 10.3390/antiox12050982.
• Liu H, Birk JW, Provatas AA, Vaziri H, Fan N, Rosenberg DW, Gharaibeh RZ, Jobin C. Correlation between intestinal microbiota and urolithin metabolism in a human walnut dietary intervention. BMC Microbiol. 2024 Nov 15;24(1):476. doi: 10.1186/s12866-024-03626-5.
• Moussa MR, Fan N, Birk J, Provatas AA, Mehta P, Hatano Y, Chun OK, Darooghegi Mofrad M, Lotfi A, Aksenov A, Motta VN, Zenali M, Vaziri H, Grady JJ, Nakanishi M, Rosenberg DW. Systemic Inflammation and the Inflammatory Context of the Colonic Microenvironment Are Improved by Urolithin A. Cancer Prev Res (Phila). 2025 Apr 1;18(4):235-250. doi: 10.1158/1940-6207.CAPR-24-0383.

Study record dates

Study Major Dates

• Study Start (Actual): January 24, 2022
• Primary Completion (Actual): January 30, 2026
• Study Completion (Actual): January 30, 2026

Study Registration Dates

• First Submitted: November 24, 2021
• First Submitted That Met QC Criteria: January 4, 2022
• First Posted (Actual): January 19, 2022

Study Record Updates

• Last Update Posted (Actual): April 17, 2026
• Last Update Submitted That Met QC Criteria: April 14, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Microbiome; Colorectal cancer; Inflammatory markers; Walnuts; Urolithin; Diet habit; Colon inflammation
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Intestinal Diseases; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Intestinal Neoplasms; Rectal Diseases; Colonic Diseases; Gastroenteritis; Behavior; Behavior, Animal; Colorectal Neoplasms; Colitis; Feeding Behavior
• Other Study ID Numbers: 21-167JS-1; 1R01CA252045-01A1 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No