Gut-Lung Axis in COPD: Investigating the Impact of Dietary Fiber Intake on Systemic Inflammation and Lung Function Decline

Abstract

Objective: The gut-lung axis represents a promising therapeutic target in chronic obstructive pulmonary disease (COPD). This study investigated whether dietary fiber intake differs between COPD patients and healthy controls, and examined its association with systemic inflammation and lung function. Methods: A case-control study was conducted including 100 COPD patients (cases) and 100 age- and sex-matched healthy controls. Dietary fiber intake was assessed using a validated food frequency questionnaire. Systemic inflammatory markers (CRP, IL-6) were measured by ELISA. Lung function parameters (FEV1, FEV1/FVC, DLCO) were evaluated according to ATS/ERS guidelines. Logistic regression analysis was performed to assess the association between dietary fiber intake and COPD risk. Results: COPD patients had significantly lower dietary fiber intake (18.30 ± 6.20 g/day) compared to controls (28.70 ± 8.10 g/day, P < 0.001). Inflammatory markers were significantly elevated in COPD patients: CRP (5.80 ± 3.20 vs. 1.20 ± 0.80 mg/L), IL-6 (8.40 ± 4.10 vs. 2.10 ± 1.30 pg/mL) (all P < 0.001). In COPD patients, dietary fiber intake was inversely correlated with CRP (r = −0.52), IL-6 (r = −0.48), and positively correlated with FEV1 (r = 0.41) and DLCO (r = 0.38) (all P < 0.001). After adjusting for confounders, low dietary fiber intake (<20 g/day) was associated with 3.2-fold increased odds of COPD (OR = 3.24, 95% CI: 1.86–5.65, P < 0.001). Conclusion: Low dietary fiber intake is significantly associated with COPD and correlates with increased systemic inflammation and reduced lung function. These findings support the potential role of the gut-lung axis in COPD pathophysiology. However, causality cannot be established due to the limitations of the cross-sectional case-control design. Prospective interventional studies are warranted to confirm these associations and evaluate whether dietary fiber modification can improve clinical outcomes in COPD patients.