A Prospective Study of Dietary Flavonoid Intake and Risk of Glioma in US Men and Women

Abstract

Background Flavonoids are a diverse group of plant constituents with demonstrated neuroprotective and anti-tumor effects. Flavonoid intake may decrease the risk of glioma, but the possibility of an association has not yet been investigated in humans. Objectives We evaluated the association between dietary flavonoid consumption and the risk of glioma. Methods We followed participants in the female Nurses Health Study (1984-2014; n = 81,688) and Nurses Health Study II (1991-2017; n = 95,228) and the male Health Professionals Follow-Up Study (1986-2014; n = 49,885). We used multivariable-adjusted Cox proportional hazards regression models to evaluate the associations between average long-term (up to 30 years) or recent (up to 12 years) dietary flavonoid intake (total flavonoids and each of 6 subclasses) and risks of incident glioma. Flavonoid intake was derived from validated quadrennial FFQs. Incident glioma was self-reported and confirmed by a medical record review or was determined by a medical record review after death. Results We documented 536 incident cases of glioma across 5,936,386 person-years of follow-up. Long-term total flavonoid, flavan-3-ol, and polymeric flavonoid (polymer) intakes were associated with decreased glioma risks in pooled analyses comparing the highest to lowest quintiles of consumption [HR, 0.79 (95% CI, 0.59-1.05; P-trend = 0.04) for total flavonoids; 0.76 (95% CI, 0.57-1.01; P-trend = 0.04) for flavan-3-ols; and 0.82 (95% CI, 0.61-1.09; P-trend = 0.05) for polymers]. Associations with recent intake were weaker. There were no associations with other flavonoid subclasses. After additional adjustment for tea consumption, there were no associations between flavan-3-ol or polymer consumption and glioma. Conclusions Increased dietary intakes of flavan-3-ol and polymeric flavonoids, especially those predominant in tea, were associated with decreased glioma risks in a prospective cohort of men and women.