Dietary Habits and Colorectal Cancer: Examining the Impact of Fruit, Vegetable, and Red Meat Consumption on Early- and Later-Onset Diagnosis in a Defined Birth Cohort

Abstract

The incidence of early-onset colorectal cancer (EoCRC) has risen over recent decades,particularly among younger adults. Shifts in dietary patterns across generations are hypothesized to contribute to this trend, yet few studies have evaluated whether associations between diet and age at CRC onset vary within a shared generational context. Using a case-case design, we analyzed data from two population-based studies comprising 1,991 adults diagnosed with CRC. We assessed average intake of fruits, vegetables, and red meat two years prior to diagnosis. Logistic regression models compared dietary intake between participants with EoCRC (18–49 years) and later-onset CRC (LoCRC, 55–74 years) in the full sample and within a birth cohort born 1948–1961, with multivariable adjustment. In the overall sample, higher vegetable intake was associated with lower odds of EoCRC (adjusted odds ratio (OR) for ≥2 servings/day compared to LoCRC: 0.72, 95% confidence interval (CI): 0.57–0.92). No significant associations were found for fruit or red meat intake. Within the birth cohort, dietary intake was not significantly associated with age at CRC onset for any dietary variable. Vegetable intake may be inversely associated with early-onset among individuals diagnosed with CRC, but this association was not observed within the specific birth cohort we examined. These findings highlight the potential influence of generational dietary exposures and support the utility of birth cohort-stratified analyses in clarifying age-related patterns in CRC onset.