Flavonoids may play an important role in the protective effects of vegetables, fruits and tea against colorectal cancer. However, associations between flavonoids and colorectal cancer risk are inconsistent, and a few studies have evaluated the effect of flavonoids from different dietary sources separately. This study aimed to evaluate associations of flavonoids intake from different dietary sources with colorectal cancer risk in a Chinese population. From July 2010 to December 2015, 1632 eligible colorectal cancer cases and 1632 frequency-matched controls (age and sex) completed in-person interviews. A validated FFQ was used to estimate dietary flavonoids intake. Multivariate logistical regression models were used to calculate the OR and 95 % CI of colorectal cancer risk after adjusting for various confounders. No significant association was found between total flavonoids and colorectal cancer risk, with an adjusted OR of 1·06 (95 % CI 0·85, 1·32) comparing the highest with the lowest quartile. Anthocyanidins, flavanones and flavones intakes from total diet were found to be inversely associated with colorectal cancer risk. Compared with the lowest quartile, the adjusted OR for the highest quartile were 0·80 (95 % CI 0·64, 1·00) for anthocyanidins, 0·28 (95 % CI 0·22, 0·36) for flavanones and 0·54 (95 % CI 0·43, 0·67) for flavones. All subclasses of flavonoids from vegetables and fruits were inversely associated with colorectal cancer. However, no significant association was found between tea flavonoids and colorectal cancer risk. These data indicate that specific flavonoids, specifically flavonoids from vegetables and fruits, may be linked with the reduced risk of colorectal cancer.
Keywords: Anthocyanidins; Case–control studies; Colorectal cancer; Flavan-3-ols; Flavonoids.