- Colorectal cancer rates have been rising in children, teens, and young adults in recent years.
- Researchers recently studied different types of diets and bacteria to see if the gut microbiome and diet impact the development of colorectal cancer.
- The scientists combined three different diets with three different bacterial strains to see what effects — if any — the diets and bacterial strain had on the gut.
- They learned that a low carb, low fiber diet combined with a particular strain of Escherichia coli can lead to an increase in polyps in the colon, which can lead to developing colorectal cancer.
Low carb diets, such as the keto diet, have increased in popularity in recent years, but many experts wonder if the health effects of a more restricted diet could have negative consequences.
Researchers from the University of Toronto in Canada recently conducted a study to explore how low carb diets can affect bacteria linked to colorectal cancer.
The researchers used mice in their study and studied them on low carb, normal, and Westernized diets and different strains of bacteria.
They focused on whether these diets impact certain bacteria and how that may contribute to colorectal cancer development.
Their study results showed that a type of Escherichia coli is negatively impacted by low carb diets. The scientists found that it increased the development of polyps. Some polyps have the potential to develop into colorectal cancer.
The study was published in
Colorectal cancer, which occurs in the colon and rectum, is one of the most
Recent data has shown that colorectal cancer cases in adults ages 30 to 34 saw an increase of 71%, and in adults ages 35 to 39, this number saw a 58% increase from 1999 to 2020.
According to the
While there is no way to guarantee that one can prevent colorectal cancer, there are some ways people can
- ceasing smoking
- limiting alcohol intake
- eating a diet that is high in vegetables, fruits, and whole grains
- limiting processed foods and red meat.
Since researchers suspect that dietary choices may be connected to the development of colorectal cancer, the new study aimed to determine whether there was a connection between specific diet types combined with certain types of bacteria.
They focused on three bacteria: Bacteroides fragilis, Helicobacter hepaticus, and E. coli, which they used to colonize the mice.
“These microorganisms cause DNA damage in intestinal epithelial cells either directly through the production of genotoxins or indirectly through the induction of DNA-damaging inflammatory mediators,” the authors explained in the study paper.
The study focused on mice that were fed low-carb and low-fiber diets, normal chow diets, and Western-style diets, which were high in fat and sugar.
After feeding the mice their specific diet types for nine weeks, the scientists checked for polyp development and then measured any polyp development again at 16 weeks.
Of the bacteria and diets tested, only the combination of the low carb diet and E. coli showed the potential to increase the risk of colorectal cancer. This is significant since, according to the study authors, E. coli is present in 60% of colorectal cancer cases.
Mice in this combination had a higher number of polyps and tumors, which can increase the risk of developing colorectal cancer. Additionally, these mice also showed DNA damage and other markers that lead to a higher risk of developing colorectal cancer.
The low carb diet thinned the mucus layer in the colon that protects against microbes. In the mice with E. coli, this allowed colibactin to reach colon cells. Colibactin is a
These mice also experienced cell senescence, which can cause cancer development. The researchers found lowered levels of regulation of gut health in the mice on low carb, low fiber diets with E. coli, contributing to inflammation.
Overall, mice on low carb diets combined with E. coli experienced such disruption and damage to their gut microbiome that researchers found it to be an environment that promotes colorectal cancer.
As concerning as these results were, the researchers found that adding fiber to these mice’s diets reduced tumor formation and helped control inflammation.
The researchers want to continue this line of research by determining whether certain types of fiber are more protective and studying their effects on humans.
Marianne Cusick, MD, an associate professor of colon and rectal surgery at UTHealth Houston, who was not involved in the recent research, spoke with Medical News Today about the study findings.
“The mouse study highlighted in the article suggests a significant potential link between low-carb diets, colibactin-producing E. coli, and colorectal cancer,“ she told us. “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.”
Cusick explained how the gut environment created by the low carb, low fiber diet, and E. coli caused “increased inflammation in the gut, a thinner mucus barrier, and a higher prevalence of polyps, which are precursors to cancer.”
While she called the findings “exciting and compelling,” she noted that further research is necessary before they can be applied to humans.
Since the study highlighted the significance of a healthy mucus barrier in the colon, Cusick mentioned some types of fiber that may help maintain that.
“Soluble fibers, such as inulin, pectin, and beta-glucan, found in grains, fruits, and vegetables, are particularly beneficial. These fibers are fermented by gut bacteria, producing short-chain fatty acids (SCFAs) like butyrate, which strengthen the mucus layer and support gut health.”
— Marianne Cusick, MD
Nilesh Vora, MD, a board certified hematologist, medical oncologist, and medical director of the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA, likewise not involved in this study, also spoke with MNT about its findings.
“I think this can be thought of as hypothesis-generating,” Vora said regarding the study. “There may be a true link here that could explain the incidence of colorectal cancer.”
Vora also acknowledged that more research is necessary on this topic but said that “the gut biome is a popular area of research in its link to colon cancer, and many study points will be emerging here.”
