Abstract
INTRODUCTION: Asthma is a multifactorial disease influenced by genetic and environmental factors, including diet. The gut microbiome contributes to airway inflammation via the gut-lung axis, partly through production of short chain fatty acids (SCFAs) from bacterial fermentation of dietary fiber. We hypothesized that dietary fiber supplementation could modulate the gut microbiome and increase SCFAs in children with asthma. METHODS: This is a double-blind, placebo-controlled trial of children who were randomized to consume 12 g of soluble corn fiber (SCF) as a supplement to their usual daily diet (50% the recommended daily fiber intake) or placebo for 4-6 weeks (clinicaltrials.gov NCT03673618). Dietary surveys, asthma symptom questionnaires, fecal, blood and nasal samples were collected before and after the intervention period to quantify fiber intake, asthma control, nasal and gut microbiome, and serum short chain fatty acids (SCFAs). RESULTS: Of the 20 children enrolled, 15 completed the intervention with an average adherence rate of 83%. SCFA concentrations and gut microbiome changes varied by individual and treatment group. No significant differences in gut or nasal alpha or beta diversity were observed between groups post-intervention. However, differential abundance analysis showed a trend toward increased Bifidobacterium in the SCF group compared to placebo (ANCOM-BC p = 0.0004, FDR q = 0.073). DISCUSSION: Supplementation of 50% of recommended daily fiber intake had minimal impact on asthma symptoms, the microbiome, or SCFA levels. Future studies should consider higher fiber doses, different fiber types, or targeting individuals with low baseline fiber intake to account for observed variability in microbiome and SCFA responses. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/study/NCT03673618, identifier NCT03673618.