A study featured in the journal Cancer Prevention Research indicates that walnuts could lower the risk of colon cancer and reduce inflammation throughout the body. “This study demonstrates that a simple, affordable diet addition can benefit colon health without significant risks,” said Daniel Rosenberg, the lead author and director of the Colon Cancer Prevention Program at the Carroll and Ray Neeg Comprehensive Cancer Center in Connecticut.
Researchers from the University of Connecticut School of Medicine discovered that walnuts have a phytochemical called eragitannin, which intestinal bacteria convert into urolysin, a strong anti-inflammatory compound. The study suggests that this transformation may influence immune cells related to colon polyps positively, aligning with a general decrease in inflammation markers found in urine, blood, and stool samples.
“The impact isn’t limited to the colon; it extends to the bloodstream,” Rosenberg observed. He further explained that this shows the effects are systemic, benefiting overall health.
The study involved 39 participants aged 40 to 60 at elevated risk for colon cancer. For one week, they refrained from consuming foods or beverages containing eragitannin, effectively reducing their levels of urolysin to near zero. Their diet was then monitored as they switched to consuming walnuts rich in yelagitannin.
After three weeks, participants underwent a high-resolution colonoscopy, where tissue samples from removed polyps were examined. The analysis revealed that individuals with higher levels of urolithin A—resulting from walnut consumption—had diminished levels of vimentin, a common protein associated with polyps.
Rosenberg noted, “Ingesting walnuts might influence inflammatory proteins around a patient’s polyp, potentially promoting health improvements.” Participants showed reduced inflammation markers in both urine and fecal samples while following the walnut-rich diet. Urolithin A was also correlated with increased levels of peptide YY, a protein known for inhibiting colorectal cancer.
Interestingly, the research found that walnut supplementation notably decreased inflammation markers in blood, particularly for individuals with a body mass index over 30. “This study highlights that adding simple, affordable foods can offer health benefits without downsides,” he reiterated.
Rosenberg pointed out that the ability to form urolithin varies significantly among individuals, with some people processing it very efficiently, while others do not. He also mentioned that the research team’s long-term aim is to identify the microorganisms responsible for this metabolic activity to potentially develop probiotics.
To reap the health benefits, Rosenberg suggests about five to ten walnuts be consumed daily.
Though not involved in the study, nutritionist Laura Feldman from Long Island University emphasized that walnuts are a fantastic source of omega-3 fatty acids, which have anti-inflammatory properties. She remarked that many Americans don’t consume enough of these essential fatty acids. Additionally, she highlighted that walnuts provide fiber, a nutrient often lacking in American diets, and that adequate fiber is associated with a reduced risk of colorectal cancer.
While walnuts are a nutritious option, Feldman cautioned that they are calorie-dense, recommending moderation, ideally sticking to one handful at a time.
