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Background: Flavonoids have been proposed to reduce the risk of Parkinson's disease (PD). However, results from epidemiological studies have been inconclusive., Objective: To prospectively examine the association between the intake of flavonoids and their subclasses and the risk of PD and how pesticides may confound or modify that association., Methods: The study population comprised 80 701 women (1984-2016) and 48 782 men (1986-2016) from two large US cohorts. Flavonoid intake was ascertained at baseline and every 4 years thereafter using a semiquantitative Food Frequency Questionnaire. We conducted multivariable-adjusted Cox regression models to estimate HRs and 95% CIs of PD according to quintiles of baseline and cumulative average intakes of flavonoids and subclasses. We repeated the analyses, adjusting for intakes of high-pesticide-residue fruits and vegetables (FVs) and stratifying by servings/day of high-pesticide-residue FV intake., Results: We identified 676 incident PD cases in women and 714 in men after 30-32 years of follow-up. Higher total flavonoid intake at baseline was not associated with a lower PD risk, neither in men (HR comparing highest to lowest quintile: 0.89, 95% CI: 0.69 to 1.14) nor in women (HR comparing highest to lowest quintile: 1.27, 95% CI: 0.98 to 1.64). Similar results were observed for cumulative average intakes and flavonoid subclasses. Results remained similar after adjustment for and stratification by high-pesticide-residue FV and when analyses were restricted to younger PD cases., Conclusion: These results do not support a protective effect of flavonoid intake on PD risk. Pesticide residues do not confound or modify the association., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)