A recently published study just confirmed that high-fat diets can alter gut bacteria and, through a domino effect, bile acids, thereby increasing the risk of colorectal cancer.
Colon Cancer
According to the American Cancer Society, colorectal cancer is the second most common cause of cancer-related deaths in the country. Approximately 153,020 individuals will be diagnosed with colorectal cancer in 2023, and 52,550 will die from it. Also, between 2020 and 2023, a 9% increase in colon cancer cases has been observed in the under-50 age group. One of the reasons that scientists suspect is the rising rate of obesity and high-fat diets. A study by the Salk Institute and UC San Diego, published in the journal Cell Reports on 22 August 2023, seems to confirm this hypothesis.
In the experiment, the team examined microbiomes and metabolomes (collections of small molecules of food and microbial origin) in the digestive tracts of mice fed a high-fat diet. Although these rodents had more bile in their intestines, the substance was less diversified and contained higher numbers of bile acids modified by gut bacteria. The researchers also observed that these modified bile acids had an impact on the proliferation of stem cells in the digestive system. “When these cells do not reconstitute frequently, they can accumulate mutations, a key step in stimulating the growth of cancers, which usually originate from these stem cells,” the authors write in a press release.
There were also significant differences in the microbiome of mice fed a high-fat diet. The gut bacteria present in their digestive tracts were less diverse and contained different bacteria than those of mice not fed a high-fat diet. Two of these bacteria – Ileibacterium Valens and Ruminococcus Gnavus – were capable of producing these modified bile acids.
The researchers believe that high-fat diets alter the composition of the microbiome, stimulating the growth of bacteria such as I. Valens and R. Gnavus. This, in turn, increases levels of modified bile acids. In a vicious circle, these bile acids create a more inflammatory environment that can further alter the composition of gut bacteria.
“We identified how a high-fat diet influences the gut microbiome and reshapes bile acid composition, driving the gut into a disease-associated inflammatory state,” explains co-author Ting Fu, a former postdoctoral researcher in the lab at the Salk Institute, in the press release.
References
Salk Institute for Biological Studies. (2023, August 22). High-fat diets alter gut bacteria, boosting colorectal cancer risk in mice. https://www.salk.edu/news-release/high-fat-diets-alter-gut-bacteria-to-boost-colorectal-cancer-risk-in-mice/
Fu, T., Huan, T., Rahman, G., Downes, M., Knight, R., & Evans, R. M. (2023). Paired microbiome and metabolome analyses associate bile acid changes with colorectal cancer progression. Cell Reports. https://doi.org/10.1016/j.celrep.2023.112997
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