This prospective, randomized controlled open-label trial evaluated the efficacy of a synbiotic consisting of partially hydrolyzed guar gum (PHGG) and Lacticaseibacillus rhamnosus GG (LGG) on clinical outcomes and gut microbiota in children with functional constipation. Children aged 4-16 years meeting Rome IV criteria were randomized to receive either synbiotic supplementation plus dietary counseling or dietary counseling alone for 12 weeks. Clinical outcomes, gastrointestinal symptoms, and stool microbiota (shotgun metagenomics) were assessed at baseline and at week 12.

Functional constipation is common in children and has been associated with gut microbiota dysbiosis and impaired short-chain fatty acid production. Synbiotics combining prebiotics and probiotics may improve stool characteristics and intestinal fermentation.

This study investigated whether daily supplementation with PHGG (4.3 g) plus LGG (1×10⁹ CFU) for 12 weeks improves stool frequency, consistency, gastrointestinal symptoms, and microbiota composition compared with standard dietary advice alone. Whole-genome shotgun metagenomics was performed in a subset of participants to characterize microbial and functional changes.

This study was registered retrospectively on ClinicalTrials.gov because it was initiated as an investigator-initiated academic study without initial intent for regulatory submission. Registration was completed after study completion to ensure transparency and compliance with journal and international reporting standards.

Inclusion Criteria:

• Age ≥4 years
• Diagnosis of functional constipation per Rome IV
• Parental informed consent

Exclusion Criteria:

• Organic causes of constipation
• Chronic medication use
• Antibiotics or biotics within 8 weeks
• Age <4 years