Collagen peptide supplementation improves skin aging parameters and modulates the gut–skin microbiota: a randomized, double-blind, placebo-controlled trial

Collagen peptides (CP) have been reported to stimulate dermal collagen synthesis through modulation of the gut microbiota in animal studies, but human evidence remains limited. This study aimed to comprehensively evaluate the clinical efficacy and multi-omics effects of oral CP in humans, integrating skin, gut, and metabolomic analyses. In this 8-week randomized, double-blind, placebo-controlled trial, 70 healthy women (39.2 ± 8.8 years) received CP, a collagen–elastin peptide mixture (MP), or placebo. Significant improvements from baseline were observed in facial wrinkle, texture, hydration, and elasticity in the CP and MP groups (wrinkle: 12.00% and 14.83%; texture: 15.21% and 16.87%; hydration: 4.36 and 4.48 units; elasticity: both 0.10 units), whereas no significant improvements were detected in the PL group (P < 0.05). No significant differences were observed between the CP and MP groups, while more pronounced improvements were detected in women older than 40 years. CP supplementation increased the abundance of Cutibacterium and Lactobacillus in the skin microbiota, and altered skin metabolite profiles, characterized by elevated N-undecanoylglycine and Pro-Pro. CP also increased the abundance of gut Roseburia and Faecalibacterium, enhanced the Gut Microbiome Wellness Index, and enriched amino acid metabolism. Skin improvements correlated with the abundance of Roseburia intestinalis, indicating a gut–skin link. These findings indicate that oral collagen peptides represent a promising strategy for improving skin aging by modulating gut–skin microbiota and metabolomic profiles.