University of Connecticut Clinical Study Finds That Eating Walnuts Daily Lowers Risk of Colon Cancer
Nikhil Prasad Fact checked by:Thailand Medical News Team Apr 29, 2025 5 hours, 20 minutes ago
Health News: New research from the University of Connecticut School of Medicine is bringing major attention to the humble walnut, suggesting it could play a key role in preventing colon cancer and reducing systemic inflammation.
Walnuts have long been recognized for their rich nutrient content, but scientists now believe they may do even more. This
Health News report highlights how eating walnuts could significantly support the body’s fight against inflammation and cancer, thanks to natural plant compounds they contain known as ellagitannins.
University of Connecticut Clinical Study Finds That Eating Walnuts Daily Lowers Risk of Colon Cancer
How Walnuts Could Help Protect Against Colon Cancer
Ellagitannins are a special group of plant-derived polyphenols. When consumed, these compounds are metabolized by gut bacteria into molecules called urolithins. Among these, urolithin A stands out for its potent anti-inflammatory and cancer-fighting properties.
Dr. Daniel W. Rosenberg, Ph.D., HealthNet Chair in Cancer Biology and an investigator at the Center for Molecular Oncology at the University of Connecticut School of Medicine, along with his multidisciplinary team, has been studying walnuts for over a decade. Their latest clinical trial found that participants who ate walnuts daily developed higher levels of urolithin A, which correlated with reduced inflammation markers in blood, urine, and even inside colon tissues.
Notably, participants who produced more urolithin A after eating walnuts showed positive changes inside their colon polyps—growths that can become cancerous. Obese individuals, in particular, experienced stronger anti-inflammatory benefits, highlighting walnuts’ potential for this high-risk group.
Inside the Clinical Trial
For the study, 39 participants between the ages of 40 and 65, all at elevated risk for colon cancer, were enrolled from the Division of Gastroenterology at UConn Health. Each volunteer underwent screening at UConn John Dempsey Hospital and completed a specialized food intake questionnaire developed by Dr. Ock Chun, Ph.D., from the College of Agriculture, Health, and Natural Resources at UConn Storrs.
Before starting walnut consumption, participants avoided foods rich in ellagitannins for one week to reset their urolithin levels to near zero. They then consumed a specific amount of walnuts each day for three weeks. At the end of the trial, each underwent a high-definition colonoscopy performed by Drs. John Birk and Haleh Vaziri.
The researchers discovered that those who produced higher levels of urolithin A also had increased serum levels of peptide YY, a protein known to inhibit colorectal cancer. They also had lower levels of harmful inflammatory markers, especially obese participants whose gut microbiomes were better able to convert walnut compounds into urolithins.
Advanced Imaging Provides Key Insights
To understand these e
ffects at the cellular level, the research team used cutting-edge high-dimensional spatial imaging to examine colon polyp tissues. They found that individuals with higher urolithin A levels had reduced expression of vimentin, a protein strongly linked to more aggressive colon cancer forms.
The levels of CD163, a protein tied to immunosuppressive macrophages that promote tumor growth, were also significantly lower. These findings suggest that walnut consumption does more than just lower inflammation—it may reshape the environment within the colon to be less hospitable to cancer development.
Building on Years of Research
The study builds on earlier animal research led by Dr. Masako Nakanishi, assistant professor in the Rosenberg Lab, who found that walnuts helped prevent colon cancer in mice. Inspired by those findings, the team moved to this human trial, seeking to verify whether similar protective effects occur in people.
“Our study proves that dietary supplementation with walnuts can boost urolithin levels in people with the right gut microbiome, while significantly reducing several inflammatory markers, especially in obese patients,” said Dr. Rosenberg. “There are so many potential benefits from eating walnuts, with so little downside risk, that grabbing a handful every day is really something easy you can do for your long-term health.”
How the Study Was Designed
Participants avoided foods like berries, pomegranates, and flaxseeds during the study and instead consumed 56 grams of whole peeled walnuts daily (about two ounces). Diet compliance was checked by analyzing urine for urolithin A levels.
Extensive bloodwork was done to measure 73 different inflammatory markers. High-definition imaging was used to evaluate changes within the colon’s cellular structure before and after walnut consumption.
What they found was striking: even short-term walnut consumption led to major shifts in inflammation and gut health markers. Those who produced more urolithin A showed stronger reductions in harmful proteins and improvements in the makeup of their colon tissues.
Key Inflammatory Changes Observed
Patients with higher urolithin A levels had significantly lower levels of important inflammatory markers like C-peptide, soluble IL-6 receptor (sIL-6R), TRAIL, soluble VEGF receptor 2 (sVEGFR2), and MCP-2. These reductions were especially prominent among obese participants, suggesting that walnuts may have an even stronger anti-inflammatory effect in people at higher risk for colon cancer.
Interestingly, there was also a rise in glucagon-like peptide 1 (GLP-1) among high BMI patients—a hormone linked to better gut health and lower inflammation, though this increase did not reach statistical significance.
Peptide YY levels, a beneficial gut hormone associated with inhibiting colorectal cancer, also rose with higher urolithin A production. Meanwhile, levels of the inflammatory cytokine TNFα showed a downward trend, both in laboratory blood cell experiments and among study participants.
Imaging Unveils How Walnuts Affect Colon Tissue
Using advanced imaging mass cytometry, researchers mapped changes inside the colon polyps at a single-cell level. They found that high urolithin A producers had fewer cells expressing vimentin and CD163, both markers linked to cancer progression.
Moreover, tissue samples from these participants had more lymphocyte clusters—immune cells associated with stronger immune responses against tumors. This suggests that walnut consumption could strengthen the body’s natural defenses inside the colon.
Conclusion
This groundbreaking clinical trial shows compelling evidence that walnuts are not just a healthy snack but a powerful tool in cancer prevention. By boosting the production of urolithin A, a potent anti-inflammatory molecule, walnuts help reduce systemic inflammation and reshape the gut environment to be less favorable for cancer growth. The study also reveals that these benefits are even greater among obese individuals, who often face higher cancer risks.
Through detailed imaging and molecular analysis, the researchers were able to prove that eating walnuts for just a few weeks could lead to visible improvements inside colon tissues, making them less prone to developing cancerous changes. The findings advocate for the inclusion of walnuts in the daily diet as a simple, effective, and low-risk strategy for improving gut health and reducing cancer risk.
With just a handful of walnuts each day, people could take an easy yet impactful step toward protecting their long-term health and wellbeing.
The study findings were published in the peer reviewed journal: Cancer Prevention Research.
https://aacrjournals.org/cancerpreventionresearch/article/18/4/235/754306/Systemic-Inflammation-and-the-Inflammatory-Context
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