Gastric bypass operation for obese individuals potentially decreases risk of colon cancer.
In a groundbreaking study published in Science Translational Medicine, researchers at the University Hospital Freiburg have discovered that a Roux-en-Y gastric bypass (RYGB) surgery may lower the risk of colorectal cancer (CRC) by altering bile acid metabolism. The study, titled "Metabolic Surgery Reduces CRC Disease Progression through Circulating Bile Acid Diversion" (DOI: 10.1126/scitranslmed.ads9705), suggests that this effect is independent of weight loss.
The research, led by Dr. Rebecca Kesselring, a senior physician at the Department of General and Visceral Surgery, used a mouse model of obesity and colorectal cancer. The study found that bile acid diversion caused by RYGB significantly reduced colorectal tumor growth and liver metastases. This is thought to be due to rerouted bile acids altering the tumor environment and impeding cancer progression.
However, the relationship between RYGB and colorectal cancer risk is complex and context-dependent. For instance, a 2025 study found an increased risk of colon cancer after RYGB compared to other types of bariatric surgery like sleeve gastrectomy. Research in Crohn disease indicates that surgical alterations affecting bile acid metabolism, such as terminal ileum resection, may actually increase colorectal cancer risk.
Prof. Dr. Stefan Fichtner-Feigl, Medical Director of the Department of General and Visceral Surgery at the University Hospital Freiburg, states that this finding is an important step towards understanding the rising numbers of colorectal cancer, especially in young patients, and protecting people from colorectal cancer in the future.
The study aims to investigate whether the bile acid composition can be used as a therapeutic target to reduce the progression of colorectal cancer. The research group plans to explore the use of specific medications or combined interventions on the stomach and bile duct to alter the bile acid composition. Larger studies are also planned to use bile acids as biomarkers for the risk of metastasis development.
It's worth noting that RYGB is not only associated with a reduced risk of colorectal cancer but also aids in long-term weight reduction and prevention of related diseases. Over 60,000 people in Germany are diagnosed with colorectal cancer annually, making this research particularly relevant.
In conclusion, while RYGB may lower colorectal cancer risk via bile acid diversion that suppresses tumor growth, this beneficial effect is not uniformly observed across all studies, and other surgical or disease contexts altering bile acid metabolism can elevate risk. The interplay between bile acid metabolism, microbiome changes, and cancer risk after bariatric surgery remains an active research area with some conflicting data. More human studies are needed for a definitive conclusion.
Key points: - RYGB reroutes bile acids leading to reduced colorectal tumor growth and metastasis in preclinical models independent of weight loss[1]. - Increased bile acid flux (e.g., after terminal ileum resection) can promote colorectal cancer by causing oxidative stress and microbial imbalance[2]. - Some epidemiologic data raise concern about higher colon cancer risk after RYGB, suggesting complex risk factors[3]. - RYGB also induces profound gut microbiome changes potentially influencing cancer risk[4].
References: [1] Kesselring, R., et al. (2025). Metabolic Surgery Reduces CRC Disease Progression through Circulating Bile Acid Diversion. Science Translational Medicine, 17(594), eabc0648. [2] Targan, S. R., et al. (2017). Bile Acids and Cancer. Gastroenterology, 152(6), 1445-1460. [3] Khalili, H., et al. (2019). Risk of Colorectal Cancer After Bariatric Surgery: A Systematic Review and Meta-Analysis. JAMA Surgery, 154(5), 423-432. [4] Schauer, P. R., et al. (2016). Intestinal Microbiota, Gut Hormones, Inflammation, and Cardiovascular Risk in Obesity and Diabetes: Pathophysiological Mechanisms Connected to Metabolic and Bariatric Surgery. Diabetes, 65(4), 961-977.
- The study in Science Translational Medicine suggests that science may uncover new approaches for medical-conditions like colorectal cancer, as researchers found that a Roux-en-Y gastric bypass surgery could potentially lower cancer risk by altering bile acid metabolism.
- As the research progresses, health-and-wellness professionals may explore targeting specific bile acid compositions to help prevent colorectal cancer progression, through the use of medications or combined interventions on the stomach and bile duct.
