New research from the University of Toronto has revealed a concerning link between low-carb, low-fibre diets and colorectal cancer risk when combined with a specific strain of E. coli bacteria.
Scientists found this dietary and bacterial combination damages the gut’s protective mucus layer, allowing harmful toxins to reach colon cells and promote the formation of polyps that can develop into cancer.
The study, published in Nature Microbiology, showed that adding fibre to the diet reduced tumour development and helped control inflammation.
The findings are particularly significant as E. coli is present in 60 per cent of colorectal cancer cases.
GETTY
The researchers conducted their study using mice, testing three different diets: low-carb and low-fibre, normal chow, and Western-style diets high in fat and sugar.
They combined these diets with three bacterial strains: Bacteroides fragilis, Helicobacter hepaticus, and E. coli.
After nine weeks, scientists checked for polyp development, with further measurements at 16 weeks.
Only the combination of a low-carb diet and E. coli showed the potential to increase colorectal cancer risk.
Mice with this combination developed more polyps and tumours and showed DNA damage and other markers indicating higher cancer risk.
The researchers discovered that the low-carb diet thinned the protective mucus layer in the colon.
In mice with E. coli, this thinning allowed colibactin, a genotoxin that damages DNA, to reach colon cells. These mice also experienced cell senescence, which can contribute to cancer development.
“The mouse study highlighted in the article suggests a significant potential link between low-carb diets, colibactin-producing E. coli, and colorectal cancer,” an associate professor of colon and rectal surgery at UTHealth Houston, told Medical News Today. “The researchers found that a low-carb diet paired with a strain of E. coli that produces colibactin led to the development of colorectal cancer in mice.”
The study found lowered levels of regulation of gut health in mice on low-carb, low-fibre diets with E. coli, creating an environment that promotes colorectal cancer through disruption and damage to the gut microbiome.
Importantly, researchers found that adding fibre to these mice’s diets reduced tumour formation and helped control inflammation.
Colorectal cancer rates have been rising significantly in younger populations in recent years, with data showing cases in adults aged 30-34 increased by 71 per cent from 1999 to 2020.
For those aged 35-39, cases rose by 58 per cent during the same period.
According to the CDC, colorectal cancer has a five-year survival rate of 64.4 per cent.
The University of Toronto researchers plan to continue their work by investigating whether certain fibre types are more protective against cancer development.
They also intend to study these effects in humans, building on their significant findings in mice.
