BACKGROUND
Dermal atrophy (DA) or skin "thinning" can cause a substantial impact on quality of life and, due to barrier function damage, further health problems including cutaneous infection, skin tears and lacerations from minor trauma, impaired wound healing and chronic dermal inflammation. Some dietary products are targeted at therapeutic and functional treatments for skin ageing (of which mild DA is a component); however, while dietary collagen is amongst the most popular, particularly in the form of collagen peptides (CPs), in contrast to reviews for both over-the-counter and under prescription topical treatments for DA (e.g. Tretinoin), there is no reviewed literature of human trials testing the efficacy of orally administered collagen treatments applicable to DA; hence this review.
OBJECTIVE
To review the literature and assess available randomised-controlled trials (RCTs) testing the efficacy of orally administered collagen treatments for any skin properties that relate to the pathophysiology of DA and suggest their potential for medical and general public use in treating DA.
EVIDENCE REVIEW METHOD
A PubMed search was conducted using "(collagen) AND (supplementation OR treatment) AND (skin OR dermis)", after which titles and abstracts were screened to decide if they matched the inclusion criteria for review. Results were collected up to 1st of August 2019 and no lower limit on the year of publication was set.
MAIN RESULTS
Five studies with a total of 430 participants were included for review, with participants aged 24-70. Four out of the five studies used female only participants. The five studies used orally administered CPs, with dosage ranging from 570 mg/d to 10 g/d, running from 8 weeks to 6 months and assessed a range of skin properties relevant to DA including dermal thickness, epidermal thickness, dermal density, dermal collagen content, dermal collagen density and dermal elasticity. One of the studies combined CPs with several antioxidant ingredients to form the treatment and the remaining 4 studies used CPs as the only active ingredient. Methods to control for potential confounders were implemented in most studies including limiting exposure to sun, implementing a pre-treatment period of 1 week or more that controlled the use of cosmetics and intake of certain medications, micronutrient supplements and nutraceuticals with those restrictions continuing for the duration of the study. Given the heterogeneity of outcome measures across studies, quantitative analysis of results was not possible. In summary, the study with the antioxidant combined supplement showed a significant improvement in dermal thickness; two of the studies showed improvement in dermal collagen or pro-collagen content; three of the studies showed improvement in dermal elasticity; three studies showed improvement in dermal density or dermal collagen density; and lastly, no human study was found with the stated objective of assessing CPs effect specifically on DA.
CONCLUSION
Although definitive mechanistic cause-effect conclusions could not be drawn from the existing studies, they are supportive of beneficial effects of oral CP intake for treating characteristics of dermal atrophy. Further elucidation of the exact mode(s) of action that the CP intake has on improving dermal thickness, dermal density, and other skin biomarkers is necessary, with larger studies including more finely divided experimental and dose-response groups.
In conclusion, rigorousness of the trials must be improved to establish a cause-effect relationship between the CP intake and the beneficial effects for the skin atrophy, however potential has been demonstrated.
Enhancement of elastin expression by transdermal administration of sialidase isozyme Neu2
