RESUMEN
PURPOSE: Studies attempting to link dietary non-enzymatic antioxidant activity (NEAC) and colorectal cancer (CRC) risk have reported mixed results. We examined this association in the Spanish Multicase-Control Study considering the likely influence of coffee and other dietary factors. METHODS: 1718 CRC cases and 3312 matched-controls provided information about diet through a validated 140-item food frequency questionnaire. Dietary NEAC was estimated for three methods [total radical-trapping antioxidant parameters (TRAP), ferric reducing/antioxidant power (FRAP) and TEAC-ABTS] using published values of NEAC content in food, with and without coffee's NEAC. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated through unconditional logistic regression models adjusted for lifestyle and dietary factors. RESULTS: Overall dietary intake of NEAC was significantly lower in cases compared to controls and associated with a significantly reduced CRC risk, in both men (ORQ5vsQ1 = 0.67, 95% CI 0.47-0.96 for FRAP) and women (ORQ5vsQ1 = 0.53, 95% CI 0.32-085 for FRAP), in multivariate models with and without the antioxidant contribution from coffee. The effect was similar for all the NEAC methods evaluated and for both colon and rectum. The association between dietary NEAC and CRC risk became non-significant when adjusting for fiber intake. However, intakes of NEAC and fiber were correlated. CONCLUSION: This study indicates that intake of an antioxidant-rich plant-based diet, both with and without NEAC from coffee, is associated with decreased CRC risk.