Flavonoid intake and survival after diagnosis of colorectal cancer: a prospective study in 2 US cohorts

Abstract

BackgroundAlthough experimental evidence supports anticancer effects of flavonoids, the influence of flavonoid intake on colorectal cancer (CRC) survival remains unknown. ObjectivesThis study aimed to assess the association of postdiagnostic flavonoid intake with mortality. MethodsWe prospectively assessed the association of postdiagnostic flavonoid intake with CRC-specific and all-cause mortality in 2552 patients diagnosed with stage I–III CRC in 2 cohort studies—the Nurses’ Health Study and the Health Professionals Follow-up Study. We assessed the intake of total flavonoids and their subclasses using validated food frequency questionnaires. We used the inverse probability–weighted multivariable Cox proportional hazards regression model to calculate the hazard ratio (HR) of mortality after adjusting for prediagnostic flavonoid intake and other potential confounders. We performed spline analysis to evaluate dose–response relationships. ResultsThe mean [standard deviation (SD)] age of patients at diagnosis was 68.7 (9.4) y. During 31,026 person-y of follow-up, we documented 1689 deaths, of which 327 were due to CRC. The total flavonoid intake was not associated with mortality, but a higher intake of flavan-3-ols was suggestively associated with lower CRC-specific and all-cause mortality, with multivariable HR (95% CI) per 1-SD increases of 0.83 (0.69–0.99; P = 0.04) and 0.91 (0.84–0.99; P = 0.02), respectively. The spline analysis showed a linear relationship between postdiagnostic flavan-3-ol intake and CRC-specific mortality (P = 0.01 for linearity). As the major contributor to flavan-3-ol intake, tea showed an inverse association with CRC-specific and all-cause mortality, with multivariable HRs per 1 cup/d of tea of 0.86 (0.75–0.99; P = 0.03) and 0.90 (0.85–0.95; P < 0.001), respectively. No beneficial associations were found for other flavonoid subclasses. ConclusionsHigher intake of flavan-3-ol after CRC diagnosis was associated with lower CRC-specific mortality. Small, readily achievable increases in the intake of flavan-3-ol–rich foods, such as tea, may help improve survival in patients with CRC.