A new study from the University of Connecticut School of Medicine has found that eating walnuts may help reduce inflammation throughout the body and lower the risk of colon cancer.
This study, which appears in the April issue of Cancer Prevention Research, adds to growing evidence that diet can play an important role in cancer prevention.
The research focused on a natural compound found in walnuts called ellagitannins. These are special plant substances that don’t do much on their own but become very powerful after being processed by bacteria in the gut.
When you eat foods like walnuts, your gut bacteria turn these ellagitannins into smaller substances called urolithins.
One type, urolithin A, has been shown to reduce inflammation and might even help stop cancer cells from growing.
Dr. Daniel Rosenberg, the lead scientist of the study, has been studying walnuts and their health benefits for over ten years.
He and his team believe that the transformation of ellagitannins into urolithin A in the gut is key to understanding how walnuts can protect against colon cancer.
Their research suggests that this natural process leads to a drop in certain inflammation markers found in the blood, urine, and stool—and may even help change how cells behave inside colon polyps, which are growths in the colon that can turn into cancer over time.
The study included 39 adults between the ages of 40 and 65 who were already at higher risk for colon cancer. Before starting the trial, participants avoided foods that naturally contain ellagitannins (like berries, pomegranates, and nuts) for one week to reduce their starting urolithin levels.
Then, they followed a special diet that included walnuts for three weeks. After that, each person had a colonoscopy, a test where doctors use a small camera to check for polyps and other signs of colon problems.
One interesting result was that people who had the highest levels of urolithin A in their urine also had higher levels of a helpful protein in their blood called peptide YY, which may help stop colon cancer from developing.
The researchers also found fewer signs of inflammation in the blood, especially in people who were overweight. These results suggest that some people—depending on the types of bacteria living in their gut—might get even more health benefits from walnuts.
Using advanced imaging tools, the team also looked closely at the polyps taken out during the colonoscopies.
They found that people who produced a lot of urolithin A had fewer harmful proteins inside their polyps, including one called vimentin that is often linked to more serious stages of colon cancer. This shows that eating walnuts might directly improve the health of colon tissue.
This clinical trial builds on earlier work by Dr. Masako Nakanishi, who had already shown in animal studies that walnuts could lower cancer risk. Her findings helped inspire this human study.
According to Dr. Rosenberg, urolithin A seems to have a strong effect on lowering inflammation and may help prevent colon cancer. He said this study proves that eating walnuts can increase urolithin A levels in people with the right mix of gut bacteria and reduce inflammation, especially in people who are overweight.
He recommends that people consider adding a small handful of walnuts to their daily diet as an easy and low-risk way to support their long-term health.
In summary, the study found that eating walnuts may help the body produce a natural anti-inflammatory substance that can lower signs of inflammation and possibly reduce the risk of colon cancer. These effects seem to be stronger in people who are able to produce more urolithin A through their gut bacteria.
The research suggests that walnuts could be a simple and healthy addition to the diet for many people, especially those who want to support their digestive and overall health.
If you care about cancer, please read studies about vitamin D and bowel cancer, and a cautionary note about peanuts and cancer.
For more health information, please see recent studies about the link between ultra-processed foods and cancer, and everyday foods to ward off pancreatic cancer.
The research findings can be found in Cancer Prevention Research.
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