Summary
A analysis published November 13, 2025 in JAMA Oncology found an association between high intake of ultra-processed foods (UPFs) and precancerous conventional adenomas in women under 50. Women with the highest UPF consumption had about a 45% greater risk of developing conventional adenomas—polyps that can progress to colorectal cancer—compared with women who ate the fewest UPFs. No link was found between UPF intake and serrated lesions.
Study design and participants
Investigators used data from more than 29,000 participants in the Nurses’ Health Study II, a cohort of female nurses who provided baseline information in 1991 and completed dietary questionnaires every four years. The analysis covered 1991–2015 with a median follow-up of 13 years. Participants averaged about 45 years old during follow-up and had undergone at least one lower endoscopy before age 50. People with prior cancer (other than nonmelanoma skin cancer) before their endoscopy were excluded.
Exposure definition
UPFs in this study included many processed breads, breakfast foods, sauces, spreads, condiments, and sugar-sweetened or artificially sweetened beverages; the investigators’ broad definition also encompassed alcohol. The highest consumption category averaged about 10 UPF servings per day versus about three servings per day in the lowest category.
Key findings
– 1,189 participants were documented with early-onset conventional adenomas; 1,598 had serrated lesions.
– Higher UPF intake was associated with an increased risk of conventional adenomas by age 50 (about 45% higher risk in the highest vs lowest intake groups).
– No association was observed between UPF intake and serrated lesions.
Interpretation and expert commentary
The study authors suggested the findings point to a possible role for UPFs in early colorectal tumorigenesis and support improving dietary quality to help reduce the rising burden of colorectal cancer in younger adults. Independent experts said the results are consistent with prior evidence linking diet, obesity, and environmental exposures to increasing colorectal cancer rates in younger people. Some experts emphasized that limiting UPFs while focusing on whole, nutrient-rich foods aligns with cancer prevention guidance.
Limitations
– Observational design cannot prove causation.
– Diet was self-reported via questionnaires and subject to measurement error.
– The UPF definition was broad and included alcohol, a known independent cancer risk factor; this could confound results.
– The cohort included only women, so findings may not generalize to men.
Why UPFs might increase risk
UPFs are industrially manufactured, often high in refined starches, unhealthy fats, added sugars, and additives (emulsifiers, artificial sweeteners) and low in fiber, vitamins, and polyphenols. These characteristics could alter the gut microbiome, increase intestinal inflammation, promote excess calorie intake and weight gain, and thereby contribute to colorectal carcinogenesis. The roles of specific additives and long-term effects remain incompletely understood.
Context
Colorectal cancer remains common in the U.S.; CDC data cited nearly 150,000 cases in 2022 and over 50,000 deaths in 2023. While incidence has declined in older adults, cases have risen among adults under 50 (roughly 2% per year in some age bands). Prior studies have linked obesity and diabetes—and, in other cohort analyses, UPF consumption—with increased colorectal cancer risk. Estimates indicate a large share of the U.S. food supply and calories consumed are ultra-processed.
Recommendations and next steps
Health organizations including the American Cancer Society recommend emphasizing nutrient-rich foods, a variety of vegetables and fruits, whole grains, limiting red and processed meats, sugar-sweetened beverages, highly processed foods, refined grains, and alcohol, and maintaining healthy weight and physical activity. Occasional indulgence is unlikely to be harmful, but frequent UPF consumption appears to carry greater risk. Future research should replicate findings in diverse populations (including men), refine UPF exposure definitions (separating alcohol), and investigate biological mechanisms such as microbiome and additive effects.
Bottom line
This study adds to growing evidence that frequent consumption of ultra-processed foods may be linked to early development of colorectal cancer precursors in younger women. Favoring whole, nutrient-dense foods and limiting routine reliance on highly processed products is consistent with current public health guidance to reduce cancer risk.
