Collagen supplementation for skin health: A mechanistic systematic review.

BACKGROUND: Over the last decade, many researchers tried to evaluate the effects of collagen supplements on skin aging and surprisingly revealed that the interventions improved skin aging parameters without any inconsistency. AIM: This systematic review assesses the literature regarding the effects of collagen supplements on skin health parameters in healthy and patient subjects, focusing on mechanisms of action. METHODS: At the first step of search in the databases, 9057 items were obtained. After removal of duplicate items, 6531 publications remained. Further screening by title and/or abstract resulted in removal of 6500 items. Finally, full texts of the 31 remained items were assessed for eligibility and 10 publications were included in this review. RESULTS: The evidences obtained from these systematic reviews indicated that oral administration of intact or hydrolyzed collagen improves clinical manifestation of skin health. Almost all of the included studies reported the beneficial effects of collagen supplementation, and no inconsistencies have been seen in this regard between studies. CONCLUSIONS: In this systematic review, three different mechanisms of action were clarified for the intervention. Direct effects of collagen peptides on fibroblasts, M2-like macrophages, and oral tolerance-related mechanisms are the possible mechanisms for the beneficial effects of collagen supplementation.