Correlation of dietary flavonoid intake with chronic bronchitis, emphysema, and asthma in U.S. adults: A large, national, cross-sectional study.

Objective: To explore the relationship between dietary flavonoids and bronchitis, emphysema and asthma.

Method: A total of 11743 United States adults were extracted from the National Health and Nutrition Examination Survey (NHANES) in 2007-2008, 2009-2010 and 2017-2018. Of these, 47.7% were male and 52.3% female. Dietary flavonoid intake assessed using FDNNS and 24-hour dietary recall data. Inclusion of demographics (gender, age, education, family income), behavioral factors (BMI, smoking, drinking status, diet), chronic disease information (diabetes, hypertension) as covariates to eliminate confounding. Stepwise logistic regression was used to analyze the association between total dietary flavonoid intake and the risk of chronic respiratory disease. Weighted quantile sum regression (WQS) was used to analyze the association between 29 dietary flavonoids and the risk of chronic respiratory disease. Restricted cubic spline was used to analyze the dose-response relationship between dietary flavonoid intake and risk of chronic respiratory disease.

Results: Stepwise logistic regression results showed that higher flavonoid intake in men was associated with a lower risk of CB and asthma (OR of CB: 0.55(0.31-0.97); OR of asthma: 0.72(0.52-0.99)), and WQS results showed a mixed health effect for total flavonoids and chronic respiratory tract in response to the 29 flavonoid fractions (OR of asthma: 0.97(0.94-0.99); OR of emphysema: 0.95(0.90-0.99)). Glycitein had the highest health contribution of 26.2% for emphysema; Eriodictyol had the highest health contribution of 32.13% for asthma, respectively. The RCS showed a dose-response relationship between flavonoids and respiratory tract health. The maximum dose for ingesting flavonoids to gain respiratory health benefits is 1500 mg/d.

Conclusion: Higher dietary flavonoid intake was associated with lower chronic respiratory risk in adult U.S. men. Also 29 dietary flavonoid components have an overall health effect on respiratory health. Glycitein and Eriodictyol may have potential health effects on the respiratory system. 1500 mg/day may be the Tolerable Upper Intake Level of dietary flavonoids for respiratory health in U.S. adults.