Composite dietary antioxidant index and the risk of colorectal cancer: Findings from the Singapore Chinese Health Study

Colorectal cancer (CRC) is a major contributor to cancer death globally. Several studies showed some protections by certain individual dietary antioxidants against CRC development. Epidemiologic data on the composite dietary antioxidant index (CDAI) in relation to CRC risk are sparse. Using the Singapore Chinese Health Study, an ongoing prospective cohort consisting of 61 321 cancer‐free participants aged 45 to 74 years at baseline, a food‐based CDAI was calculated according to a previously established and validated method that included six food‐sourced antioxidants including vitamins A, C and E, manganese, selenium and zinc. Cox proportional hazard regression method was used to estimate the hazard ratios (HRs) and their 95% confidence intervals (CIs) for CRC associated with various levels of CDAI with adjustment for multiple potential confounders. After an average of 17.5 years of follow‐up, 2140 participants developed CRC. HRs (95% CIs) of CRC for quartiles 2, 3 and 4 of CDAI were 0.94 (0.83‐1.07), 0.86 (0.75‐1.00) and 0.80 (0.66‐0.98), respectively, compared to the lowest quartile (Ptrend = .02). This inverse association between CDAI and CRC risk was more apparent in women or those without a history of diabetes, without family history of CRC, never smokers or overweight/obese individuals. However, none of the heterogeneity tests for the CDAI‐CRC risk association reached statistical significance. Our findings suggest that food‐based antioxidants may be beneficial for reducing the risk of CRC in the general population. What's new? Epidemiological studies on individual dietary antioxidants such as vitamins and minerals and the risk of colorectal cancer have produced inconsistent results. In this large prospective Asian cohort study, the authors apply a recently developed composite dietary antioxidant index (CDAI) that includes vitamins A, C and E, manganese, selenium and zinc. The analysis shows that a higher CDAI is associated with a lower risk of developing CRC overall. These findings support the notion that food‐based antioxidants may offer a beneficial effect and provide a potential strategy for the primary prevention of colorectal cancer.