WASHINGTON (dpa-AFX) - Recent research has revealed a troubling connection between low-fiber diets, specific gut bacteria, and colorectal cancer. Scientists at the University of Toronto found that when these factors interact with certain genetic conditions, they form what experts describe as a 'perfect storm' for cancer development.
'Colorectal cancer has always been thought of as being caused by a number of different factors, including diet, gut microbiome, environment and genetics,' said senior author Alberto Martin, a professor of immunology at U of T's Temerty Faculty of Medicine.
'Our question was, does diet influence the ability of specific bacteria to cause cancer?'
Led by Martin and postdoctoral fellow Bhupesh Thakur, the research team discovered that a diet low in carbohydrates and fiber significantly raises the risk of colorectal cancer when paired with particular strains of E. coli. Specifically, these strains produce a toxin called colibactin, which damages DNA. Notably, colibactin-producing E. coli are present in about 60 percent of colorectal cancer cases.
With low-carb diets growing in popularity, these findings are especially relevant. While such diets may aid in weight loss, they could have unintended health risks if fiber intake is inadequate.
The study examined three bacterial species associated with colorectal cancer - Bacteroides fragilis, Helicobacter hepaticus, and the E. coli strain NC101. However, only E. coli in combination with a low-carb diet had a major impact on polyp formation, which are abnormal growths that often become cancerous.
During the research, the scientists studied mice colonized with one of three bacterial species previously linked to colorectal cancer. These mice were fed either a normal diet, a low-carb diet, or a Western-style diet.
The results found that only the combination of a low-carb diet and colibactin-producing E. coli led to colorectal cancer development. Mice on this diet developed significantly more colon polyps than those on other diets. When infected with colibactin-producing E. coli, polyp formation increased even further, with many showing signs of turning cancerous.
The researchers also found that fiber deficiency led to increased gut inflammation and disrupted the balance of gut microbes. This created conditions that favored the growth of colibactin-producing E. coli.
Additionally, the inflammation triggered by a low-fiber diet increased nitric oxide production, leading to higher nitrate levels in the gut, further accelerating E. coli growth and its harmful effects.
'These findings could help inform dietary recommendations, probiotic safety guidelines and targeted prevention strategies for high-risk individuals,' Martin said.
'But at this point, I would agree it would be premature to recommend specific diets to lower the risk of colon cancer.'
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