Colorectal cancer: More evidence that Western-style diet may increase risk

Colorectal cancer (CRC) is any cancer affecting the colon, hence “colo,” and rectum, hence “rectal”. It is the third most common and second deadliest diagnosed cancer in the United States, claiming over 50,000 lives every year.

Researchers from Brigham and Women’s Hospital in Boston, MA recently observed that CRC tumors with high levels of pks+ E. coli bacteria correlate with diets rich in red and processed meats and empty calories.

They believe that unhealthy foods may stimulate the cancer-inducing activity of colibactin, a substance deriving from E. coli, in the gut.

Their findings appear in Gastroenterology.

Dr. Shuji Ogino, chief of the Molecular Pathological Epidemiology Program in the Department of Pathology at Brigham and Women’s Hospital, was the study’s corresponding author.

E. coli, colibactin, and diet

E. coli is a normal part of the gut microbiome. However, certain strains of this bacterium hold a distinct cluster of genes known as the polyketide synthase (pks) island.

These pks+ E. coli strains produce colibactin, a toxic metabolite that can damage DNA and trigger cellular mutations that promote CRC.

Consumption of a typical Western diet — also sometimes called an “American diet” — consisting mainly of red and processed meats, sugar, and refined carbohydrates, can cause intestinal and systemic inflammation, precursors to colorectal tumors.

A poor diet is also tied to an imbalance of intestinal microbiota, another factor related to CRC. Furthermore, prior studies have linked E. coli and other bacteria to this cancer.

Consequently, Dr. Ogino and his team suspected that a Western diet might induce a stronger risk for tumors with considerable amounts of pks+ E. coli. Up to this point, though, they did not know whether the diet’s correlation with CRC varies by gut bacteria.