Summary:
Cases of colorectal cancer diagnosed before age 50 are rising. Many of these early cases occur in individuals without a family history or known genetic predisposition, suggesting that environmental and lifestyle factors are contributing. Behaviours such as low physical activity, excess body weight, type 2 diabetes, and diets low in fiber but high in processed meats and added sugars have all been linked to higher risk. Consumption of ultraprocessed foods has also increased substantially and is a large proportion of total energy intake in high-income countries. Ultraprocessed foods are industrially produced products that contain few whole-food components and often include additives, refined starches, and unhealthy fats while providing little fiber or micronutrients. These characteristics may influence gut bacteria, promote intestinal inflammation, and contribute to the biological mechanisms involved in colorectal tumour development, yet the research on the impact is unclear. To address this gap, a prospective analysis was conducted which includes women born between 1947 and 1964. Participants completed a baseline dietary questionnaire, had undergone at least one lower endoscopy before age 50, and had no history of cancer, colorectal polyps, or inflammatory bowel disease. Ultraprocessed food intake was assessed every four years using food-frequency questionnaires. The study examined whether greater consumption of ultraprocessed foods was associated with early-onset neoplasia. Over 24 years of follow-up, 29,105 women contributed data, with 1,189 early-onset adenomas and 1,598 lesions identified. Ultraprocessed foods made up roughly one-third of total daily energy intake. Higher intake was associated with a significantly greater risk of early-onset adenomas, with the top intake group showing about 45% higher odds compared with the lowest intake group. These results remained stable after adjusting for body mass index, type 2 diabetes, and several dietary quality indicators. Overall, the findings suggest that frequent consumption of ultraprocessed foods is linked to increased risk of early colorectal changes in younger adults. This adds to the evidence that diet quality may influence the rising incidence of early-onset colorectal cancer and highlights opportunities for prevention through reducing intake of ultraprocessed foods.
Abstract:
Importance Early-onset colorectal cancer (EOCRC) (diagnosed age <50 years) incidence is increasing globally, in parallel with increased consumption of ultraprocessed foods (UPFs). The role of UPFs in early-onset colorectal neoplasia remains underexplored. Objective To evaluate the association between UPF consumption and risk of EOCRC precursors. Design, Setting, and Participants This prospective cohort study included participants of the Nurses’ Health Study II, an ongoing US prospective cohort of female registered nurses established in 1989. Participants were followed up from June 1, 1991, through June 1, 2015. Data were analyzed from October 2024 to July 2025. UPF intake, derived from food-frequency questionnaires administered every 4 years and classified using the Nova system, was modeled as quintiles of energy-adjusted servings per day. Of the nurses enrolled, those who had completed the baseline 1991 food-frequency questionnaire, undergone at least 1 lower endoscopy before age 50 years after baseline, had no history of cancer (except for nonmelanoma skin cancer) before endoscopy, and no colorectal polyp or inflammatory bowel disease were included. Main Outcomes and Measures Incidence of EOCRC precursors, including conventional adenomas and serrated lesions, confirmed via medical records and pathology reports. Multivariable logistic regression models with generalized estimating equations for clustered data were used to estimate adjusted odds ratios (AORs) and 95% CIs, accounting for known and putative risk factors. Results Among 29 105 female participants (mean [SD] age, 45.2 [4.5] years) over 24 years of follow-up, 1189 cases were documented of early-onset conventional adenomas and 1598 serrated lesions. UPFs provided 34.8% of total daily calories (median, 5.7 [IQR, 4.5-7.4] servings per day). Participants with higher UPF intake had an increased risk of early-onset conventional adenomas (highest vs lowest intake: AOR, 1.45; 95% CI, 1.19-1.77; overall P < .001) but not serrated lesions (AOR, 1.04; 95% CI, 0.89-1.22; P = .48 for trend). Findings were consistent after further adjustment for body mass index, type 2 diabetes, dietary factors (fiber, folate, calcium, and vitamin D), and Alternative Healthy Eating Index–2010 score. Conclusions and Relevance In this study, higher UPF intake was associated with increased risk of early-onset colorectal conventional adenomas. These data highlight the important role of UPFs in early-onset colorectal tumorigenesis and support improving dietary quality as a strategy to mitigate the increasing burden of EOCRC.
Article Publication Date: 13/11/2025
DOI: 10.1001/jamaoncol.2025.4777
