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Toronto, Canada – A new study from the University of Toronto has found that low-carbohydrate diets may increase the risk of colorectal cancer by enhancing the DNA-damaging effects of certain gut microbes. The research, published in Nature Microbiology, highlights the potential dangers of long-term adherence to a low-carb, low-fiber diet.
The study compared the effects of three different diets—normal, low-carb, and a Western-style diet high in fat and sugar—on colorectal cancer development in mice colonized with specific gut bacteria. The findings revealed that a low-carb diet, when paired with a strain of Escherichia coli (E. coli) that produces colibactin, led to the development of colorectal cancer.
The Role of Gut Microbes in Cancer Development
Professor Alberto Martin, the study’s senior author and an immunology expert at U of T’s Temerty Faculty of Medicine, explained that colorectal cancer has long been associated with a combination of factors including genetics, diet, and the gut microbiome.
“Our question was, does diet influence the ability of specific bacteria to cause cancer?” Martin said.
The study, led by postdoctoral fellow Bhupesh Thakur, found that mice on a low-carb diet exhibited increased inflammation and alterations in their gut microbiome. The diet also thinned the protective mucus barrier in the colon, allowing colibactin-producing E. coli to interact more directly with colon cells, leading to genetic damage and tumor growth. These effects were particularly pronounced in mice with genetic mutations in the mismatch repair pathway, a system that helps fix damaged DNA.
Potential Implications for Cancer Prevention
The research is particularly relevant for individuals with Lynch syndrome, a hereditary condition that increases the risk of colorectal cancer. Martin suggests that people with this condition may benefit from avoiding low-carb diets or undergoing antibiotic treatment to reduce colibactin-producing bacteria in their gut.
Interestingly, the study also found that supplementing a low-carb diet with soluble fiber helped counteract the harmful effects of colibactin-producing E. coli. This suggests that dietary modifications, such as increasing fiber intake, could mitigate the risks associated with a low-carb diet.
Thakur and Martin are now collaborating with researcher Heather Armstrong at the University of Alberta to investigate whether soluble fiber, such as inulin, can help reduce levels of colibactin-producing E. coli in high-risk individuals, including those with inflammatory bowel disease.
Raising Awareness on Dietary Risks
The findings raise concerns about the long-term effects of low-carb, low-fiber diets, which have become popular for weight loss. “More work is needed, but we hope that it at least raises awareness,” Martin emphasized.
As research continues, experts stress the importance of a balanced diet that includes sufficient fiber to maintain gut health and potentially reduce cancer risk.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Individuals concerned about their diet and cancer risk should consult a healthcare professional for personalized guidance.
