Oral Lactobacillus and Bifidobacterium probiotics improve pulmonary function and reduce inflammatory markers in COPDProbiotics May Improve Lung Function in COPD Patients

BACKGROUND AND AIMS: Chronic obstructive pulmonary disease (COPD) is a prevalent chronic respiratory disorder characterized by irreversible airflow limitation, persistent systemic inflammation and impaired quality of life. The gut-lung axis theory highlights the regulatory role of intestinal microbiota in pulmonary inflammation, and oral probiotics are regarded as promising nutritional adjuvants for COPD treatment. However, consistent evidence regarding their impacts on pulmonary function and systemic inflammatory biomarkers in COPD patients remains insufficient. This systematic review and meta-analysis aimed to evaluate the effects of probiotic supplementation on pulmonary function parameters and inflammatory indicators among COPD patients. METHODS: Following PRISMA guidelines and the Cochrane Handbook, we searched seven Chinese and English biomedical databases (PubMed, Embase, Web of Science, Cochrane Library, CNKI, SinoMed, Wanfang) up to March 20, 2026 for eligible trials evaluating oral Lactobacillus and Bifidobacterium probiotics in COPD patients, with pulmonary function and inflammatory biomarkers as primary outcomes. Two independent reviewers completed literature screening, data extraction, and methodological quality evaluation via Cochrane RoB 2 tool. All pooled analyses were conducted in Stata 18.0; meta-regression and sensitivity analyses were applied to explore heterogeneity and verify result stability, and the GRADE framework was used to assess overall evidence certainty. RESULTS: Thirteen RCTs involving 920 participants were included. Compared with control treatments, probiotic supplementation modestly elevated forced expiratory volume in 1 s (FEV) (MD = 0.26, 95% CI: 0.19-0.32, P < 0.001) and forced vital capacity (FVC) (MD = 0.35, 95% CI: 0.25-0.45, P < 0.001). Meanwhile, probiotics reduced circulating C-reactive protein (CRP) (MD = -2.37, 95% CI: -4.28 to -0.46, P = 0.01) and tumor necrosis factor-α (TNF-α) (Hedges' g = -1.93, 95% CI: -3.13 to -0.73, P < 0.001). Marked inter-study heterogeneity was observed in analyses of inflammatory biomarkers. CONCLUSIONS: Probiotic supplementation may represent a promising adjunct nutritional strategy for improving selected pulmonary function parameters and modulating systemic inflammatory responses in patients with COPD. Nevertheless, the certainty of current evidence is limited by variations in probiotic formulations, intervention protocols, and patient characteristics. Further large-scale, well-designed nutritional intervention trials are required to determine the optimal probiotic strains, dosage, and duration for COPD management.