Dietary total antioxidant capacity and colorectal cancer: a large case-control study in Italy

A favorable role of fruit and vegetables on colorectal cancer risk has been related to the antioxidant properties of their components. We used data from an Italian case-control study including 1,953 patients with incident, histologically confirmed colorectal cancer (1,225 colon and 728 rectal cancers). Controls were 4,154 patients admitted to hospital for acute, non-neoplastic conditions. A reproducible and valid food frequency questionnaire was used to assess subjects' usual diet. Total antioxidant capacity (TAC) was measured using Italian food composition tables in terms of ferric reducing-antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC) and total radical-trapping antioxidant parameter (TRAP). We estimated the odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) through multiple logistic regression models, including terms for potential confounding factors, and energy intake. TAC was inversely related with colorectal cancer risk: the OR for the highest versus the lowest quintile was 0.68 (95% CI, 0.57-0.82) for FRAP, 0.69 (95% CI, 0.57-0.83) for TEAC and 0.69 (95% CI, 0.57-0.83) for TRAP. Corresponding values, excluding TAC deriving from coffee, were 0.75 (95% CI, 0.61-0.93) for FRAP, 0.76 (95% CI, 0.61-0.93) for TEAC and 0.71 (95% CI, 0.57-0.89) for TRAP. The inverse association was apparently-though not significantly-stronger for rectal than for colon cancer. This is the first case-control study indicating consistent inverse relations between dietary TAC and colorectal cancer risk.