A recent study from researchers at Harvard T.H. Chan School of Public Health has found that alterations in the gut microbiome and metabolites persist for over a decade after the removal of an adenoma—a precancerous growth—potentially contributing to an increased risk of colorectal cancer (CRC). Published on May 27, 2026, in Cell Host & Microbe, this research highlights the role of diet and physical activity in influencing these microbial changes, particularly in individuals with a history of adenomas.
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Colorectal cancer is the second leading cause of cancer-related deaths worldwide. Although removing adenomas is an effective preventative measure, individuals who have undergone this procedure continue to face a heightened risk of developing CRC. The mechanisms behind this increased risk have been unclear, but the gut microbiome is suggested to be a significant factor.
Mingyang Song, the study's corresponding author and associate professor of clinical epidemiology and nutrition, noted that this research is the first to investigate the long-term effects of adenoma removal on gut microbiota. The findings indicate that the removal of an adenoma does not revert the gut to a low-risk state, reinforcing the gut microbiome's potential impact on sustained CRC risk.
Utilizing data and stool samples from participants in the Nurses’ Health Study II, researchers examined the gut microbiomes of 354 women with a history of adenoma removal, comparing them to 354 adenoma-free participants matched by age and background. The stool samples were collected approximately 12 years post-removal.
The study observed significant microbiome and metabolomic differences between the two groups. Participants with a history of adenoma exhibited gut bacteria profiles resembling those of CRC patients. Furthermore, among those with a prior adenoma, a less healthy diet and reduced physical activity were correlated with higher levels of CRC-associated microbes, indicating that lifestyle factors may play a critical role in microbial composition in this high-risk group.
First author Ana Nogal, a postdoctoral research fellow in the Department of Epidemiology, emphasized the implications of these findings. The long-lasting changes in gut microbiome profile suggest they may be linked to sustained CRC risk, and lifestyle modifications could potentially influence the gut environment for those at higher risk.
The research concludes that while associations were identified, further studies are necessary to explore whether adjustments to the gut microbiome through diet and exercise can effectively lower the risk of CRC.
The study was supported by the National Institutes of Health, among other organizations. Several researchers involved in the study hold positions or have received funding from various pharmaceutical companies.