Efficacy and safety of hydrolyzed collagen supplementation on skin health outcomes: a systematic literature review of randomized controlled trials.

Oral hydrolyzed collagen (HC) supplementation is widely recommended for improving age-related skin changes. However, clinical evidence remains inconsistent. This systematic literature review (SLR) synthesizes the findings from randomized controlled trials (RCTs) evaluating the efficacy, safety, and quality of life (QoL) outcomes of HC supplementation in adults. We systematically searched Embase, MEDLINE, and MEDLINE In-Process from inception through April 1, 2023, to identify RCTs assessing oral HC versus placebo or active comparators. Outcomes of interest included skin hydration, elasticity, wrinkles, transepidermal water loss (TEWL), safety, and QoL. Risk of bias was assessed using Cochrane Risk of Bias v2.0, and results were synthesized descriptively. Twenty-five RCTs (sample sizes ranging from 13 to 236 participants) were included. While most studies were conducted in healthy volunteers, seven studies enrolled patients with chronic disease conditions. HC supplementation demonstrated significant improvements over placebo in key skin parameters: skin hydration (improved in 10 of 15 trials), skin elasticity (10 of 13 trials), and wrinkle depth or volume (9 of 10 trials). Results regarding TEWL were less consistent. HC supplementation was generally well-tolerated, with a low incidence of adverse events. QoL outcomes, assessed in seven studies primarily among osteoarthritis or rheumatoid arthritis patients, showed variable improvements depending on the assessment tool and study population. The majority of included trials were rated as having a high risk of bias. Preliminary evidence suggests that HC supplementation may offer dermatological benefits, but high-quality, standardized, adequately powered, and longer-term RCTs are needed to confirm its efficacy and safety.