A newly spotlighted bacterial toxin, colibactin—produced by certain strains of Escherichia coli (E. coli)—may be fueling the worrying surge in bowel cancer among younger adults, according to groundbreaking research published in the journal Nature this April. With diagnoses of bowel cancer in individuals under age 50 rising sharply, experts are racing to unravel the factors behind this unexplained trend, which also affects Thai society as local incidence rates climb and public concern increases.
The global surge in bowel cancer among those under 50—the so-called “early onset” cases—has alarmed doctors and health officials. In the UK, the number of cases in this age group has soared by over 20% in recent decades, while similar patterns have been observed in the United States, Australia, and parts of Southeast Asia, including Thailand. Traditionally linked to advanced age, family history, and lifestyle factors such as obesity, heavy drinking, and high-fat diets, bowel cancer is now striking many younger people who do not fit this classical risk profile (The Telegraph).
Until recently, much of the focus has been on dietary and environmental causes. However, a team led by the University of California San Diego, along with international collaborators, has identified colibactin, a DNA-damaging toxin made by specific strains of E. coli, as a potential culprit. E. coli is a common resident of the human gut—most strains are harmless and even beneficial—but “pks+” strains harbor genes that produce colibactin.
Speaking about the research, the genetics section head at the International Agency for Research on Cancer explained that colibactin is “thought to be a defense mechanism”—part of the bacteria’s arsenal for outcompeting other microbes. Yet, this defense has a cost for humans: colibactin can directly attack DNA in the cells lining the bowel, sowing mutations that lay the groundwork for cancer.
A key finding from the recent study is that the genetic “signature” of colibactin-induced DNA damage was 3.3 times more common in patients who developed bowel cancer before age 40 than in those diagnosed after age 70. According to the group leader of the Stem Cell and Cancer Biology Laboratory at the Francis Crick Institute, “This suggests a strong link between colibactin exposure and early onset bowel cancer.” Another prominent researcher, director of the Centre for Evolution and Cancer at The Institute of Cancer Research, described the link as “clear” but urged caution: colibactin is “a potential culprit,” and more proof is needed to confirm causality.
The question of how people—especially children—become exposed to these dangerous E. coli strains is still open. The cancer genetics co-investigator for Cancer Research UK’s Cancer Grand Challenges project highlighted that “if mutations occur within the first weeks of life then this would implicate exposures around childbirth and weaning.” Research is now focused on potential exposures from contaminated food, untreated water, and even probiotics, some of which may use colibactin-producing bacteria.
In Thailand, where food safety is an ongoing concern and waterborne diseases persist in some communities, these findings may have special resonance. While there is no evidence yet linking Thai probiotic products or national dietary patterns to colibactin exposure, food hygiene and access to safe drinking water remain public health priorities (World Health Organization). The presence of “bad” E. coli in raw or undercooked foods is a familiar risk, particularly with traditional dishes that incorporate raw meat, fish, or unpasteurized dairy.
Currently, it is impossible for individuals to test whether their gut harbors colibactin-producing bacteria outside of a research setting, and there is no routine screening for colibactin-related DNA mutations. Nevertheless, laboratories are beginning to develop early detection tests that analyze stool samples, which could revolutionize how risk is assessed in the future.
In the meantime, experts suggest that practical steps remain crucial in lowering the risk of bowel cancer. Among them: increasing dietary fiber intake through more fruit, vegetables, legumes, and whole grains—a strategy well supported by studies worldwide. Such foods not only speed up transit time for waste in the digestive tract (reducing exposure of the bowel lining to potential toxins) but also promote the growth of gut bacteria that convert fiber into butyrate. This beneficial compound helps protect bowel cells from tumor development (Cancer Research UK).
Thai dietary habits, which often feature abundant vegetables, rice, and fermented products, may confer some protection. However, rising urbanisation and Westernization of diets—characterized by more red and processed meats and less traditional fiber-rich fare—threaten to dilute these benefits. According to nutrition surveillance by the Ministry of Public Health, fiber consumption among Thai adolescents and young adults has fallen significantly in the last ten years.
Regular exercise, maintaining a healthy weight, and limiting alcohol and tobacco use are also key to prevention. The importance of early symptom recognition is echoed by stakeholders in many countries. Signs such as unexplained changes in stool patterns, persistent diarrhea or constipation, abdominal pain, or blood in stool should prompt an immediate visit to a health professional. The head of cancer prevention at Bowel Cancer UK stressed, “No matter how old you are, if you notice anything that isn’t normal for you, don’t ignore it, speak to your doctor. In most cases it won’t be cancer, but if it is, spotting it early can make a real difference.”
In Thailand, awareness campaigns led by the Department of Disease Control routinely emphasize early screening, but coverage gaps remain, especially for populations outside official screening ages. Several private hospitals now offer at-home fecal immunochemical tests (FIT) for young adults with persistent symptoms, but cost and stigma—discussion of bowel habits is often a taboo subject—limit their widespread adoption.
Historically, the Thai perspective on bowel cancer risk has prioritized inherited factors and lifestyle, with little public attention paid to gut microbes. However, Thai microbiome research, such as that conducted by Chulalongkorn University’s Center of Excellence in Microbial Genomics, is catching up. Recent initiatives have started to map the typical bacterial profiles of Thais in different regions and explore links to chronic disease, including cancer (Chulalongkorn University source).
Looking forward, the implications of the colibactin discovery are considerable. Further research may clarify whether interventions—ranging from targeted probiotics to improved hygiene and food supply monitoring—could lower the risk posed by these bacteria. As the director of the Centre for Evolution and Cancer notes, “We don’t have a treatment available, or know if removal of the bugs would be beneficial to prevent bowel cancer, or even if there could be other unintended consequences.” This caution is important: the delicate balance of the human microbiome means that interventions must be carefully evaluated for both benefits and risks.
For Thailand, the practical message is clear. While scientific discovery advances the broader understanding of early-onset bowel cancer, everyday choices still matter. Individuals are encouraged to:
- Increase dietary fiber by consuming more vegetables, beans, fruits, and whole grains, in line with the Thai Health Promotion Foundation’s ongoing campaigns.
- Practice rigorous hygiene, especially when preparing raw foods or consuming street food. Washing hands, using safe water, and cooking food thoroughly are simple yet crucial steps.
- Recognize and act on concerning digestive symptoms, regardless of age, by seeking prompt medical advice.
- Engage in regular exercise and avoid excessive alcohol consumption and processed meats.
As evidence grows around the role of colibactin and other bacterial toxins in bowel cancer, Thailand’s health system and public must stay vigilant and informed. By combining wise choices with robust food safety and science-backed policy, the country can protect future generations from one of the most preventable—and increasingly treatable—forms of cancer.
Sources:
- The little-known toxin that could be behind the rising rates of bowel cancer in under-50s (The Telegraph)
- What is bowel cancer? (Cancer Research UK)
- Colibactin and mutational signatures in colorectal cancer (Nature)
- World Health Organization Thailand—Water Safety
- Chulalongkorn University—Microbiome Research
- Thai Health Promotion Foundation—Fiber campaign