Dietary Collagen Supplementation as a Strategy for Skin Health: A Narrative Review of Clinical Effects on Skin, Hair, Nails, and Wound Healing.

Collagen is a key structural protein of the skin, essential for maintaining its mechanical strength, elasticity, and hydration. Oral collagen supplementation, particularly in the form of collagen peptides, has recently gained significant interest as a nutritional strategy to support skin health and overall wellbeing. However, the evidence regarding its effectiveness in supporting skin health and improving hair, nail, and wound-healing outcomes remains heterogeneous. The aim of this review is to summarize and critically evaluate the current human evidence on oral collagen supplementation and its potential role in supporting skin health, hair and nail quality, and wound healing. A targeted literature search was conducted using PubMed and Web of Science to identify clinical trials and relevant studies assessing the effects of collagen supplementation on skin aging parameters, including elasticity, wrinkles, hydration, and barrier function, as well as hair loss, nail disorders, and wound healing. Collagen-derived peptide supplementation has been associated with improvements in skin hydration, elasticity, wrinkle appearance, and dermal extracellular matrix organization, while also supporting hair thickness and strength, modestly enhancing nail growth, and promoting wound healing. Benefits are most consistent with low-molecular-weight hydroxyproline-rich peptides, with peptide characteristics appearing more important than collagen source. Evidence is limited by short study durations, heterogeneous designs, multi-ingredient formulations, and industry funding, which reduce confidence in the magnitude and consistency of the reported effects. Nevertheless, high-quality, long-term, independently funded trials with standardized outcomes are still required to confirm these findings.