A prospective study of dietary flavonoid intake and risk of glioma in US men and women.

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.
(© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition.)