"Low-Carbohydrate Diet, Increased Risk of Colorectal Cancer with Long-Term Adherence"

University of Toronto Research Team Conducts Mouse Experiments
Low-Carbohydrate Diets in Fiber-Deficient Environments
Promote Gut Microbial Activity and Growth of Colon Polyps

Many people seek low-carbohydrate diets for weight loss, but a study has found that long-term adherence to such diets can promote the activity of certain gut microbes, increasing the risk of colorectal cancer. Dong-A Science reported, "A research team led by Professor Albert Martin from the University of Toronto, Canada, published these findings on the 3rd (local time) in the international journal Nature Microbiology."

The research team studied the effects of low-carbohydrate, high-fat, and regular diets on the gut microbial ecosystem and colorectal cancer development through mouse experiments. In particular, they grew specific bacteria related to colorectal cancer in the mice's intestines and observed how the bacteria changed depending on the diet consumed. As a result, mice on a low-carbohydrate diet showed increased intestinal inflammation and disrupted gut microbial balance, leading to the growth of colon polyps, unlike mice on other diets. Colon polyps are precancerous lesions that can develop into cancer.

Subsequent analysis of the gut microbial environment revealed that a bacterium called Escherichia coli (E. coli) promoted the growth of colon polyps. This bacterium produces a DNA-damaging substance called colibactin, which adversely affects colon cells.

Professor Martin, who led the study, explained, "Colorectal cancer is known to be a disease influenced by multiple factors, but this study confirmed that a low-carbohydrate diet can affect the cancer-causing ability of specific bacteria," adding, "In an environment lacking dietary fiber, E. coli bacteria grow, causing DNA damage in the colon and ultimately leading to colorectal cancer."

Conversely, when the research team supplemented dietary fiber in the low-carbohydrate diet, the number of cancer-causing bacteria decreased, DNA damage was reduced, and the risk of colorectal cancer was lowered. The team stated, "Supplementing dietary fiber was able to mitigate the negative effects of the low-carbohydrate diet," and added, "We plan to study which types of dietary fiber are more beneficial."

The low-carbohydrate diet was also found to weaken the mucus layer between gut microbes and colon epithelial cells, increasing the chances of bacteria contacting intestinal cells. The mucus layer acts as a kind of "protective barrier" separating gut bacteria from colon cells, and when this layer thins, DNA damage occurs more easily, raising the risk of cancer.

Professor Martin emphasized, "Low-carbohydrate diets are often chosen by people aiming for weight loss, but maintaining them long-term can pose health risks," and stated, "This study serves as an important warning that such diets may increase the risk of colorectal cancer."