Childhood Gut Toxin Exposure Linked to Colorectal Cancer in Adulthood, Study Reveals
By Adebowale Bello. B.Tech Microbiology, Freelance Health Writer. Medically reviewed by: A. Odutola, MB.BS, PhD, FRCSEd.
Cartoon illustration of the commonest location of colon cancer in the large bowel.
Over the past two decades, more young people under 50 are being diagnosed with colorectal cancer, a disease once thought to affect mainly older adults. This trend has puzzled health experts and led to several investigations into possible causes.
Recently, a groundbreaking study by researchers at the University of California, San Diego, shed new light on what might be contributing to this worrying rise. The study suggests that early-life exposure to a bacterial toxin known as colibactin could be playing a major role.
While most of the research focused on Western populations, the findings carry important implications for African communities where early exposure to gut-related infections and poor sanitation are common.
Understanding this connection could help us take action early and protect future generations from this preventable disease.
The research was carried out by a team of scientists and they analysed the genetic data of 981 colorectal cancer patients from 11 different countries. They focused on the presence of a specific toxin called colibactin, which is produced by certain strains of Escherichia coli (E. coli) bacteria commonly found in the gut.
E. coli is not always harmful. In fact, it is a normal part of the gut microbiome. However, some strains carry genes that enable them to produce colibactin, a chemical that damages the DNA of cells lining the colon. Over time, this damage can cause cells to become cancerous.
What makes colibactin particularly dangerous is that it leaves a unique fingerprint or “signature” on the DNA it damages. The researchers used advanced tools to search for this signature in the tumour DNA of colorectal cancer patients.
The most insightful discovery from the study was that younger patients (those under 40) were far more likely to have tumours that showed signs of damage caused by colibactin. In fact, they were 3.3 times more likely to have this specific DNA signature compared to patients over the age of 70.
The researchers also found that the presence of colibactin-related mutations was higher in countries where early-onset colorectal cancer is on the rise. This suggests that people in these regions may have been exposed to colibactin-producing bacteria early in life, possibly through food, water or poor sanitation.
Moreover, the damage caused by colibactin appeared to take place years before the cancer was actually diagnosed. This means the harmful exposure may have happened in childhood, long before any symptoms showed up.
In many African communities, children are often exposed to unsanitary conditions and untreated drinking water, both of which can increase the risk of gut infections. E. coli is one of the most common bacteria found in contaminated food and water, and children are particularly vulnerable to repeated exposure.
If certain strains of E. coli in African environments produce colibactin, this could be silently damaging the colon lining of children across the continent. Over time, and without early screening, this damage may develop into cancer during adulthood.
This study highlights the urgent need to improve sanitation, promote handwashing and ensure access to clean drinking water. These basic but powerful public health measures could reduce the transmission of harmful E. coli strains and potentially lower the risk of early-onset colorectal cancer.
Our diets also play a significant role in maintaining a healthy gut microbiome. Diets low in fibre and high in processed foods can increase inflammation in the gut and allow harmful bacteria to thrive. Encouraging the consumption of fruits, vegetables, legumes and whole grains may help protect the colon from long-term damage.
A Historical Parallel: What Peptic Ulcers Can Teach Us about Colon Cancer
The idea that a bacterial toxin could quietly damage the colon and trigger cancer decades later may seem surprising. This would not be the first time however, that medical science has been forced to revise its understanding of a major disease due to bacterial involvement.
Before the 1980s, peptic ulcers were largely blamed on stress, spicy foods and excess stomach acid and patients were told to avoid certain meals, reduce their stress levels and rely on antacids for relief.
It wasn’t until the groundbreaking work of two Australian researchers, Barry Marshall and Robin Warren, that this long-standing belief was turned on its head. They discovered that a bacterium called Helicobacter pylori was not just present in ulcer patients but was the main cause.
Their work, which initially faced heavy resistance, eventually transformed ulcer treatment worldwide. Antibiotics became the mainstay of therapy, and H. pylori became the gold standard for causation.
What we are now seeing with E. coli and its colibactin toxin could be a similar turning point in how we understand colorectal cancer, particularly among young adults. Could it be that for decades we’ve overlooked a microbial factor, focusing instead on lifestyle changes, diet or genetics alone?
The parallels are striking. Both H. pylori and colibactin-producing E. coli live in the digestive tract. Both can cause chronic, low-grade damage that may go unnoticed for years and both have the potential to leave molecular footprints that lead to serious disease outcomes, either through inflammation or direct DNA damage.
If future studies confirm the strong role of colibactin in triggering colon cancer, it would mark a seismic shift in our understanding, much like what happened with peptic ulcers. It would also open new doors for prevention, diagnosis and treatment, especially through microbiome management and targeted bacterial eradication.
This new study presents compelling evidence that a bacterial toxin produced by E. coli may be silently increasing the risk of colorectal cancer in young people. For Africans, this is particularly concerning due to widespread exposure to unhygienic conditions during childhood. While more research is needed locally, the findings offer a warning and a chance to act early.
Improving sanitation, promoting healthy diets, and encouraging early screening can make a real difference. As the saying goes, prevention is better than cure. It is time we look deeper into our gut health, not just as a matter of comfort, but as a matter of life and death.
Source: Díaz-Gay, M, dos Santos, W, Moody, S. et al. Geographic and age variations in mutational processes in colorectal cancer. Nature (2025). doi: 10.1038/s41586-025-09025-8. Available from here
Related:
Colon cancer: Symptoms, Causes, Risk factors, Diagnosis Treatment and Prevention
Colon cancer rates and deaths are rising among younger Americans, study says.
Colorectal Cancer in Africa: A Fact-sheet
Published: June 12, 2025
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