A new study published in JAMA Oncology has identified a strong link between ultra-processed foods and an increased risk of precancerous polyps in women under 50. Researchers analyzed data from the Nurses’ Health Study II, which has tracked the health of tens of thousands of women since 1989.
The analysis focused on 29,105 female participants under 50 who had no prior cancer, inflammatory bowel disease, or colorectal polyps at the start. Every four years, the women reported their dietary habits, and researchers classified foods by level of industrial processing. Ultra-processed foods include packaged breads, sweetened beverages, flavored yogurts, breakfast cereals, snack foods, and ready-to-eat meals.
The findings showed a clear pattern: women who consumed the highest amounts of ultra-processed foods, about 5.7 servings per day, had a 45% higher risk of developing precancerous polyps compared to those who ate the least. This association was specific to conventional adenomas, the type of polyp most likely to become colorectal cancer over time. The same link was not found for serrated lesions.
The foods most strongly associated with increased risk included sugar-sweetened beverages, ready-to-eat meals, processed meats, breakfast cereals, packaged breads, and bottled condiments. These are common convenience foods that many people eat regularly.
Possible mechanisms
Researchers do not yet claim that ultra-processed foods directly cause colorectal cancer, but they have several hypotheses. Ultra-processed foods are known to trigger chronic low-grade inflammation throughout the body, including the gastrointestinal tract. Inflammation can create an environment where cells accumulate DNA damage and mutations, early steps toward cancer.
These foods also disrupt the gut microbiome. They tend to be low in fiber and high in additives such as emulsifiers and artificial sweeteners, which can reduce microbial diversity and promote harmful bacteria. Additionally, many ultra-processed foods contain advanced glycation end products (AGEs), compounds linked to oxidative stress and inflammation.
Implications for women’s health
With early-onset colorectal cancer rising and screening still recommended to start at age 45, prevention becomes important. The study notes that reducing ultra-processed staples such as packaged breads, sweetened yogurts, cereals, flavored coffee creamers, and bottled sauces can help. Prioritizing fiber-rich whole foods, keeping sugary drinks to a minimum, and choosing products with shorter ingredient lists are recommended.
Warning signs for colorectal cancer include persistent changes in bowel habits, blood in the stool, unexplained weight loss, ongoing abdominal cramping, or unusual fatigue. When caught early, colorectal cancer has a survival rate above 90%.
The study focused exclusively on white female nurses, so more diverse research is needed to understand how these findings apply across different racial, ethnic, and socioeconomic groups. Genetics, healthcare access, environmental factors, and cultural food traditions all play a role. The core message is that diet may change cancer risk years before symptoms appear.
