Scientists Reveal Snack That May Slash Colon Cancer Risk

New research from the University of Connecticut School of Medicine suggests that a simple daily snack could play a significant role in reducing the risk of colon cancer.

Published in the journal Cancer Prevention Research, the study is one of the first human clinical trials to link walnut consumption to measurable anti-inflammatory and anti-cancer effects in the colon.

According to the Centers for Disease Control and Prevention (CDC), in 2021 there were 141,902 new cases of colorectal cancer reported—and, in 2022, 52,967 people died from the disease.

The American Cancer Society (ACS) estimates that in 2025, there will be about 107,320 new cases of colon cancer (54,510 in men and 52,810 in women) and about 46,950 new cases of rectal cancer.

But how can a simple snack like walnuts decrease the risk of colon cancer? The secret lies in "ellagitannins," naturally occurring plant compounds found in walnuts.

The study was led by University of Connecticut environmental pharmacologist professor Daniel Rosenberg led the study, which was supported by the American Institute for Cancer Research, the California Walnut Commission, and the National Cancer Institute.

Rosenberg explained that natural compounds in walnuts are converted by gut bacteria into powerful anti-inflammatory molecules called "urolithins"—especially urolithin A.

"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," he added.

The clinical trial involved 39 patients between the ages of 40 and 65, all considered at elevated risk for colon cancer. Participants were first screened and then asked to eliminate ellagitannin-rich foods from their diets before consuming walnuts daily over a three-week period.

Their inflammatory markers were monitored through blood, urine, and stool samples, and colon polyps were examined through high-definition colonoscopies.

Among the study's key findings was that people who produced more of the compound urolithin A after eating walnuts had lower levels of inflammation in their bodies—especially those who were obese, a group typically at higher risk for colon issues. These participants also showed increased levels of peptide YY, a hormone that has been linked to lowering the risk of colorectal cancer.

The research team also used advanced imaging technology to take a closer look at tissue from colon polyps that were removed during colonoscopies. What they found was striking:

"Patients with high levels of urolithin A formation following walnut consumption was directly associated with reduced levels of several important proteins that are often present in polyps," the team reported.

One of those proteins, vimentin—which is often seen in more advanced cases of colon cancer—was "greatly reduced inside polyp tissues obtained from patients who had also formed the highest levels of urolithin A."

This study builds upon earlier research in mice led by professor Masako Nakanishi, which first suggested walnuts could reduce cancer risk. Those findings paved the way for this human clinical trial.

"Urolithin A has a very positive influence on inflammation and maybe even cancer prevention," Rosenberg said.

"Our study proves that dietary supplementation with walnuts can boost the general population's urolithin levels in those people with the right microbiome, while significantly reducing several inflammatory markers, especially in obese patients."

He added: "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."