Association of dietary fiber intake with current asthma and recent asthma outcomes: a cross-sectional analysis of National Health and Nutrition Examination Survey 2017–March 2020 pre-pandemic data

Abstract

Objective: Dietary fiber may influence asthma through the gut-lung axis and systemic inflammation, but evidence in contemporary U.S. adults remains limited.

Methods: We analyzed 6,145 adults aged 20 years or older from National Health and Nutrition Examination Survey 2017–March 2020 pre-pandemic data using a common complete-case sample for the staged regression models. Day-1 dietary fiber was the primary exposure; a separate 2-day mean sensitivity analysis was conducted in 5,364 participants with a reliable second recall. Survey-weighted logistic regression assessed current asthma, asthma attacks and asthma-related acute-care visits with adjustment for demographic, socioeconomic, lifestyle, energy-intake and clinical covariates; body mass index (BMI) was evaluated separately. False-discovery-rate correction across the three outcomes and multiple imputation were used as sensitivity analyses.

Results: Current asthma was present in 596 participants (weighted prevalence, 8.7%). Each 1-standard-deviation increase in Day-1 fiber was associated with lower odds of current asthma in the primary model (odds ratio [OR], 0.80; 95% confidence interval [CI], 0.64–0.99; P = 0.043), but not after false-discovery-rate correction (q = 0.129). BMI adjustment yielded OR 0.82 (95% CI, 0.66–1.02; P = 0.076). Separate repeated-recall and multiple-imputation analyses were directionally consistent (2-day mean: OR, 0.74; 95% CI, 0.61–0.90; multiple imputation: OR, 0.81; 95% CI, 0.66–0.99). Fiber was not associated with asthma attacks or acute-care visits.

Conclusion: Higher reported fiber intake showed an inverse association with current asthma, but statistical evidence was modest after multiple-outcome correction. Repeated-recall and missing-data analyses were directionally consistent. Cross-sectional design, reverse causation and residual confounding preclude causal interpretation.