A study published November 13, 2025 in JAMA Oncology reports an association between higher intake of ultra-processed foods and increased risk of precancerous colorectal polyps in women under 50. Women with the highest consumption had about a 45% greater risk of developing conventional adenomas—polyps that can progress to colorectal cancer—than women with the lowest intake.
Study design and key results
Researchers used medical records and repeated dietary questionnaires from more than 29,000 participants in the Nurses’ Health Study II. Women enrolled provided baseline information in 1991 and completed diet surveys every four years through June 2015; median follow-up was 13 years. All participants had at least one lower endoscopy before age 50 and no prior cancer history (except nonmelanoma skin cancer).
Ultra-processed foods in the analysis were mainly processed breads, breakfast foods, sauces, spreads, condiments, and sugar-sweetened or artificially sweetened drinks. Women in the highest intake group averaged roughly 10 servings per day versus about three servings per day in the lowest group. During follow-up researchers identified 1,189 cases of early-onset conventional adenomas and 1,598 serrated lesions. High ultra-processed food intake was linked to an increased risk of conventional adenomas but showed no clear association with serrated lesions.
Limitations
The investigators and outside experts note several limitations: the cohort included only women, dietary intake was self-reported, and the definition of “ultra-processed” was broad. Alcohol was classified as an ultra-processed item in this analysis; because alcohol itself raises cancer risk, future work should separate the effects of alcohol from other ultra-processed foods.
What experts say and possible mechanisms
Outside commentators said the findings are consistent with prior research connecting unhealthy diets, obesity, and environmental exposures to rising colorectal cancer in younger adults. Potential mechanisms proposed include the low fiber, vitamin, and polyphenol content of many ultra-processed foods and their high content of unhealthy fats, refined starches, sugars, and additives (for example, emulsifiers and artificial sweeteners). These features may alter gut microbiota, increase intestinal inflammation, and promote conditions that favor carcinogenesis. Ultra-processed foods also tend to drive excess calorie intake and weight gain, established risk factors for colorectal cancer.
Broader context and public health implications
Previous studies have linked high ultra-processed food consumption to increased colorectal cancer risk in men and women and to sizable numbers of preventable deaths in the U.S. National estimates and dietary surveys indicate a large share of U.S. calories comes from ultra-processed products. The CDC reported nearly 150,000 colorectal cancer cases in 2022 and more than 50,000 deaths in 2023. Although overall incidence and mortality remain higher in men, rates have been rising in younger adults—about 2% per year for some age groups—making earlier onset a growing concern.
Practical recommendations
Cancer and public health organizations recommend limiting ultra-processed foods and focusing on whole, nutrient-dense choices to lower cancer risk. Common guidance includes: eat a variety of vegetables and fruits and choose whole grains; favor nutrient-rich foods that support a healthy weight; limit red and processed meats, sugar-sweetened beverages, highly processed foods, refined grain products, and alcohol; and stay physically active while reducing sedentary time. Clinicians often stress frequent healthy eating rather than occasional treats—occasional processed-food indulgences are less concerning than habitual high intake.
Next steps
Further research is needed to confirm biological mechanisms, test whether results apply to men, and separate the specific contribution of alcohol from other ultra-processed foods. For now, the study adds to a growing body of evidence suggesting that reducing habitual consumption of ultra-processed products may help lower the risk of precancerous colorectal lesions in younger adults.
