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In a study conducted by the NIH-AARP Diet and Health Study, researchers examined the connection between food processing and dietary risk factors and colorectal cancer (CRC) incidence in older US adults. Ultra-processed foods (UPF) make up 50% of energy intake among US adults and can contain dietary elements linked to both lower and higher CRC risk.

The study aimed to estimate the associations of UPF and recognized CRC-related dietary factors, divided by UPF and non-UPF sources, with CRC incidence. Participants, aged 50-71, who enrolled in the study between 1995-96, reported their dietary intake using a food frequency questionnaire (FFQ). The median UPF intake was 293 grams per 1000 kcal/day, or 43% of daily energy intake.

Researchers assigned disaggregated FFQ items to Nova classification and categorized UPF intake into sex-specific quintiles. A total of 10,075 CRC cases were diagnosed among participants cancer-free at baseline. Using multivariable-adjusted Cox proportional hazards regression models, the study adjusted for demographic, lifestyle, and health-related factors to estimate the associations between UPF and related dietary components with CRC incidence.

Results showed that UPF intake was not associated with CRC incidence (hazard ratio for 5th versus 1st quintile 0.97; 95% confidence interval [0.91--1.03]; p trend = 0.55). However, UPF sources contributed to overall fiber, whole grain, dairy, and calcium intakes, which were inversely linked to CRC incidence. In contrast, meat intake from UPF sources was positively associated with CRC risk.

Limitations of the study include its observational design, potential residual confounding, and exposure misclassification due to systematic or random error in self-reported dietary data. Despite these limitations, the findings support current dietary guidance to consume whole grains, fiber, dairy, and calcium and avoid processed meat for CRC prevention.