Chronic inflammation is one of the causes of colorectal cancer (CRC), and circulating levels of inflammatory biomarkers have been linked to tumor promotion and progression. We aimed to evaluate the interleukin-6 (IL-6) level in CRC patients and determine whether a diet rich in antioxidants was associated with CRC. This study included 654 cases and 1312 controls matched for age and sex. We measured the plasma IL-6 concentration and estimated dietary antioxidant capacity based on oxygen radical absorbance capacity (ORAC) combined with a 106-item semiquantitative food frequency questionnaire. The IL-6 concentration was significantly increased in individuals with CRC (OR Q4 vs. Q1, 95% CI = 6.23, 4.10-9.45, p < 0.001). High dietary ORAC showed an inverse association with CRC (total ORAC OR Q4 vs. Q1, 95% CI = 0.26, 0.16-0.40, p < 0.001; total phenolics = 0.32, 0.21-0.50, p < 0.001). We found that low dietary ORAC was associated with a significant increase in CRC in the group with elevated IL-6 levels (total ORAC OR Q4 vs. Q1, 95% CI = 4.34, 3.12-6.02, p < 0.001; total phenolics = 4.61, 3.33-6.39, p < 0.001). This study suggested an inverse association between dietary antioxidant capacity and IL-6 level among patients with CRC.
Keywords: antioxidants; colorectal cancer; inflammation; interleukin-6; oxygen radical absorbance capacity.