Bowel cancer rates among people under 50 are rising, prompting scientists to investigate a range of potential causes, including diet, antibiotics, and environmental factors. Researchers are examining how changes in gut bacteria, exposure to chemicals, and lifestyle habits may contribute to this trend.
One key area of focus is dietary fiber intake. Fiber promotes the production of butyrate, a substance created when gut bacteria break down fiber from fruits, vegetables, and whole grains. Butyrate helps maintain a healthy bowel lining, reduces inflammation, and regulates cell growth. Studies have indicated that butyrate can slow the progression of bowel cancer cells by influencing gene activity related to cell division. Conversely, diets low in fiber may cause gut bacteria to degrade more protein, generating substances that could harm the bowel lining.
Nutrition researchers are also exploring the impact of additives like emulsifiers, commonly found in processed foods such as sauces and ice cream. Some evidence suggests that certain emulsifiers may disrupt gut health and promote inflammation. For instance, Katy Lander, diagnosed with bowel cancer at 32, reflected on her pre-diagnosis diet, which included convenience foods with low fiber and many additives. Since her diagnosis, she has increased her intake of fiber-rich foods, aiming for about 30 grams per day.
Antibiotic use is another suspected factor. Prescriptions rose sharply during the 1980s in England and globally among young children, with a study linking antibiotics to a 49% increased risk of bowel cancer in people under 50. Antibiotics can disrupt the balance of gut bacteria by reducing both harmful and beneficial microorganisms, potentially allowing damaging bacteria to flourish. Colorectal surgeon Professor James Kinross notes that harmful bacteria can trigger inflammation, which damages the bowel lining and increases the likelihood of DNA replication errors during cell repair.
Researchers have identified a strain of E. coli bacteria that produces colibactin, a compound capable of damaging DNA in bowel cells years before cancer develops. Unlike typical food-poisoning strains, pks-positive E. coli can reside in the bowel without symptoms and are carried by roughly 20% of healthy individuals. Studies show that DNA damage associated with colibactin is more frequent in patients diagnosed before age 40 than in older patients, suggesting early exposure may provide a genetic "headstart" for cancer development.
Beyond bacteria and diet, environmental toxins are also under investigation. A study found a possible link between the weedkiller picloram and bowel cancer in younger adults, noting higher bowel cancer rates in U.S. regions with extensive picloram use. Another concern involves PFAS ("forever chemicals") used in non-stick cookware and waterproof fabrics. Laboratory research has shown that PFAS chemicals can increase the mobility of bowel cancer cells, a trait linked to tumor spread. Historical data indicates that PFOA levels in human blood more than doubled from the 1970s to the late 1980s, raising questions about long-term exposure effects.
Microplastics, detected in bowel tumors, are also being examined for their potential to irritate the bowel lining, induce inflammation, and disrupt gut bacteria. Children may be especially vulnerable since they consume more microplastics relative to body weight and have still-developing immune and organ systems.
Despite these investigations, the precise reasons behind the rise in bowel cancer among younger people remain unclear. Individuals like Katy Lander, now cancer-free but cautious of recurrence, highlight the ongoing impact on patients' lives. While researchers continue exploring causes, experts advise focusing on overall metabolic health and dietary habits, including increasing fiber intake, to potentially reduce risk.