Dietary phytochemical index and biomarker profiles are associated with colorectal cancer odds: integrating dietary intake with blood biomarkers

Abstract

Background Colorectal cancer (CRC) remains a major global health challenge. Phytochemical-rich diets may influence colorectal carcinogenesis through antioxidant, anti-inflammatory, metabolic, and gut barrier-related mechanisms. However, evidence simultaneously integrating dietary phytochemical intake with other biologically relevant markers remains limited. This study investigated the association between the dietary Phytochemical Index (PI) and CRC odds. Methods This hospital-based case–control study included 490 patients with newly diagnosed CRC and 490 cancer-free controls. Dietary intake was assessed using a validated FFQ, and the PI was calculated as the percentage of total energy derived from phytochemical-rich foods. Fasting blood samples were analyzed for gut barrier, inflammatory, oxidative stress, metabolic, nutritional, and tumor-related biomarkers. Multivariable logistic regression assessed the association between PI and CRC, while linear regression and exploratory mediation analyses evaluated biomarker associations and potential pathways. Results Mean PI was significantly lower among patients with CRC than controls (p < 0.001). In the fully adjusted model, each one-unit increase in PI was associated with lower odds of CRC (OR = 0.946, 95% CI: 0.909–0.984; p = 0.006). Compared with the lowest tertile, participants in the highest PI tertile had lower odds of CRC (OR = 0.480, 95% CI: 0.298–0.773; p = 0.003; p for trend = 0.002). Higher PI was statistically associated with lower concentrations of inflammatory and oxidative stress biomarkers. In exploratory mediation analyses conducted within the limitations of the case–control design, statistical indirect associations were identified involving inflammation, oxidative stress, and gut barrier function. However, because biomarker concentrations were measured after CRC diagnosis, these analyses cannot establish temporal or causal relationships and are presented solely for hypothesis generation, not as evidence of biological mediation. Conclusion Higher dietary phytochemical intake was independently associated with lower CRC odds and favorable biomarker profiles. These findings suggest an inverse association between phytochemical-rich dietary patterns and CRC, though prospective studies are needed for confirmation. Given the simultaneous assessment of diet, biomarkers, and disease status in this cross-sectional design, these findings are hypothesis-generating and require independent validation in prospective cohorts.