"The effects of topical vitamin C on the skin BY FIRAS AL-NIAIMI / POSTED IN DERMATOLOGY ON JANUARY 20, 2016
Firas Al-Niaimi reviews the evidence surrounding the mechanisms of action, applications, and future use of topical formulations of vitamin C….
Vitamin C is the most abundant antioxidant in human skin1. The importance of vitamin C for our health was signified in 1937 by Dr Albert von Szent-Györgyi who won the Nobel prize for discovering vitamin C deficiency as the main cause of scurvy2. Unlike plants and some animals, humans are unable to synthesize vitamin C due to the absence of an enzyme called L-glucono-gamma lactone oxidase. Therefore, we rely entirely on oral supplementation either in the form of tablets or diet (citrus fruit and green leafy vegetables), and topical application in the case of cosmeceuticals for the skin3. With increasing evidence of the protective effects of vitamin C and its derivatives on the skin, vitamin C has become a popular cosmeceutical agent.
Biochemically, vitamin C has a 5-hydrocarbon ring similar to that of fructose4. When ingested in usual doses of up to 100 mg per day, complete absorption of vitamin C occurs in the distal small intestine. The plasma half-life is reported to be between 8–40 days. With higher levels of intake, more rapid renal excretion occurs and the half-life is thought to decrease markedly to about 30 minutes5. Absorption of oral vitamin C is limited by active transport mechanism and despite high doses of oral supplementation, only a small fraction of it will eventually be biologically available and active in the skin. Hence, for any discernible role of its actions in the skin, vitamin C needs to be supplied topically2." continue reading here.