Fatty food raises risk of colorectal cancer

A new study has established a direct link between high-fat diets and an elevated risk of developing colorectal cancer, according to research conducted by scientists in Germany. Published in the August 2026 edition of the journal Gut, the findings suggest that Western-style diets rich in fatty foods contribute to the proliferation of specific gut bacteria that produce a secondary bile acid known to promote tumor growth. This discovery marks a critical step in understanding the biological mechanisms behind the rising incidence of colorectal cancer among younger adults. Researchers from the Technical University of Munich, RWTH Aachen, and the German Institute of Human Nutrition Potsdam-Rehbrücke (DIfE) identified that diets high in fat sustain particular strains of gut bacteria capable of converting primary bile acids into deoxycholic acid (DCA). This compound, when present in high concentrations within the colon, increases the likelihood of abnormal cell division, thereby raising the risk of colorectal cancer. The study was led by Annika Osswald, a PhD student at DIfE, who emphasized that the research provides clear evidence of causality rather than mere correlation. The investigation began with experiments on laboratory mice. Scientists introduced DCA-producing bacteria into the intestines of mice with fully controlled microbiomes. They then induced colorectal cancer in two groups, one with the bacteria and one without. Mice harboring the DCA-producing bacteria exhibited greater tumor growth compared to those without the bacteria. Additionally, cells in the affected mice showed increased rates of division, a factor that heightens the probability of genetic mutations leading to cancer. To confirm whether similar processes occur in humans, the researchers examined stool samples from over 1,000 individuals, both with and without colorectal cancer. They found that genes associated with DCA-producing bacteria were more prevalent in individuals diagnosed with the disease. This finding underscores the role of dietary habits and gut microbiota composition in influencing cancer risk. The implications of this study extend beyond individual health choices. Colorectal cancer has been noted as the only type of cancer where mortality rates have risen among those under 50 in recent decades. According to data published in the Journal of the American Medical Association in January 2026, while death rates from other major cancers such as brain, breast, leukemia, and lung cancer have decreased since 1990, colorectal cancer fatalities have increased by approximately 1.1% annually since 2005. Although the United States represents just one geographic area, its trends are often used as indicators for global patterns. Sören Ocvirk, a microbiologist and co-author of the study, highlighted the significance of understanding how Western diets influence gut health. He pointed out that the changes in the gut microbiome due to high-fat consumption could have far-reaching consequences for overall health. The study’s authors acknowledge that further research is necessary to explore potential therapeutic interventions based on these findings. The research team stressed that their work serves as a foundation for future studies aimed at mitigating the effects of harmful dietary practices. By identifying the causal relationship between DCA-producing bacteria and tumor growth, the study opens avenues for developing targeted treatments for colorectal cancer. As the prevalence of this disease continues to rise, particularly among younger populations, the need for effective prevention strategies becomes increasingly urgent.