Higher consumption of ultraprocessed foods is associated with an increased risk of early colorectal tumour precursors in women younger than 50 years, according to a large long-term study that adds to concerns about modern dietary patterns and rising bowel cancer rates.
The incidence of early-onset colorectal cancer has been increasing worldwide, a trend that has coincided with growing intake of ultraprocessed foods. While these foods are known to contribute to obesity and metabolic disease, their role in early bowel tumour development has remained uncertain.
Long Term Cohort And Dietary Assessment
The prospective cohort study analysed data from the Nurses’ Health Study II, which has followed female registered nurses in the United States since 1989. The analysis included 29 105 participants who completed dietary questionnaires in 1991, underwent at least one lower endoscopy before age 50 years, and had no prior history of cancer or colorectal disease.
Participants were followed for up to 24 years, with ultraprocessed food intake assessed every 4 years using validated food-frequency questionnaires. Foods were classified according to the Nova system and analysed in quintiles of energy-adjusted servings per day. On average, ultraprocessed foods accounted for 34.8% of daily calorie intake, with a median of 5.7 servings per day.
Increased Risk Of Conventional Adenomas
During follow-up, 1189 cases of early-onset conventional adenomas and 1598 serrated lesions were confirmed through medical records and pathology reports. Women in the highest quintile of ultraprocessed food intake had a 45% higher odds of developing conventional adenomas compared with those in the lowest quintile.
The association remained statistically significant after adjustment for multiple risk factors, including body mass index, type 2 diabetes, fibre, folate, calcium, vitamin D intake, and overall diet quality. No association was observed between ultraprocessed food intake and serrated lesions, suggesting a specific link to the conventional adenoma pathway.
Implications For Cancer Prevention
Conventional adenomas are well-established precursors to colorectal cancer, making their prevention a key target for reducing future disease burden. The findings suggest that dietary patterns high in ultraprocessed foods may contribute to early tumour development well before cancer is diagnosed.
Researchers conclude that reducing ultraprocessed food consumption could be an effective strategy to help prevent early-onset colorectal tumourigenesis. Improving overall dietary quality, particularly among younger adults, may play an important role in addressing the growing public health challenge of colorectal cancer diagnosed before age 50 years.
Reference
Wang C et al. Ultraprocessed food consumption and risk of early-onset colorectal cancer precursors among women. JAMA Oncol. 2025; 10.1001/jamaoncol.2025.4777.
