Is a Handful of Walnuts a Day the Secret to a Healthier Gut and Colon? Study Sheds Light - Video

New clinical trial results from the UConn School of Medicine reveal that consuming walnuts may reduce systemic inflammation and help lower the risk of colon cancer. The findings, published in Cancer Prevention Research, underscore the health-promoting effects of ellagitannins, polyphenols found in walnuts that are metabolized by the gut microbiome into powerful anti-inflammatory compounds called urolithins.

The research, led by Dr. Daniel W. Rosenberg and a multidisciplinary team at UConn, highlights the unique role of urolithin A—formed in the gut after walnut consumption—as a key anti-inflammatory agent with potential cancer-inhibiting properties. “Ellagitannins in the walnut are importantly providing the anti-inflammatory and anti-cancer properties that we’re seeing in patients in our clinical trial research, particularly the gut’s conversion of ellagitannins to a potent anti-inflammatory agent, urolithin A,” said Dr. Rosenberg, who has studied walnut health benefits for over a decade.

In the study, 39 participants aged 40 to 65, all at elevated risk for colon cancer, followed a controlled diet that included ellagitannin-rich walnuts after eliminating similar foods for a week. Researchers closely monitored biomarkers from blood, urine, and fecal samples before and after the three-week walnut intervention.

The results showed higher levels of urolithin A in urine correlated with increased levels of peptide YY—a protein associated with colon cancer inhibition—and reduced markers of inflammation, especially in obese participants who produced more urolithins. Advanced imaging of polyps removed during post-study colonoscopies showed fewer cancer-linked proteins in patients with higher urolithin levels. Notably, the cancer-associated protein vimentin was markedly reduced in these patients.

Building on prior findings in mice, the human study supports walnuts as a dietary tool for cancer prevention. “Urolithin A has a very positive influence on inflammation and maybe even cancer prevention,” said Rosenberg. “Our study provides strong rationale for dietary inclusion of walnut ellagitannins for cancer prevention. Nutrients from walnuts can contribute to reduced cancer risk. There are many potential benefits one can get from eating walnuts, with so little downside risk, that just grabbing a handful every day is really something that you can easily do for your long-term health benefit.”

Reference: Marmar R. Moussa, Nuoxi Fan, John Birk, Anthony A. Provatas, Pratik Mehta, Yuichiro Hatano, Ock K. Chun, Manije Darooghegi Mofrad, Ali Lotfi, Alexander Aksenov, Vinicius N. Motta, Maryam Zenali, Haleh Vaziri, James J. Grady, Masako Nakanishi, Daniel W. Rosenberg; Systemic Inflammation and the Inflammatory Context of the Colonic Microenvironment Are Improved by Urolithin A. Cancer Prev Res (Phila) 1 April 2025; 18 (4): 235–250. https://doi.org/10.1158/1940-6207.CAPR-24-0383