Together, the included reviews covered 113 randomised controlled trials and 7,983 patients, providing a broad overview of the current clinical evidence base for collagen supplementation and skin health. 

The authors reported that oral collagen supplements have been associated with improvements in skin hydration, elasticity and wrinkles, with some studies also suggesting positive effects on dermal density. However, they noted that findings vary across formulations, study designs and outcome measures. 

The review highlights that collagen supplements differ considerably in source, dose, molecular weight, additional ingredients and duration of use, making direct comparison between products difficult. 

The authors conclude that collagen supplementation may offer benefits for skin ageing, but emphasise the need for more standardised, high-quality research to clarify which formulations, dosages and treatment durations are most effective.