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Keys to Unlocking the Benefits of Vitamin C
By: Lawrence Samuels, MD
Posted: November 29, 2012, from the December 2012 issue of Skin Inc. magazine.
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Equally important for the penetration and benefits of a vitamin C product is proper packaging. Vitamin C oxidation is due to the reaction between oxygen and light—especially UV rays. UV rays are the portion of light absorbed by vitamin C, which causes the oxidation of L-ascorbic acid. Some topical vitamin C preparations often lack stability when exposed to air and light, which causes oxidation of the L-ascorbic acid, not only making it ineffective, but also causing it to potentially increase the formation of free radicals. The bottom line: The presence of vitamin C in a product does not guarantee its effectiveness.
To produce an effective vitamin C preparation, a temperature- and light-controlled room should be used and as much air as possible should be expelled from the container prior to packaging. This produces a stable aqueous formulation of L-ascorbic acid in an appropriate 20% free acid concentration with a pH of 3.0 +/- 0.4 to maximize biologic activity and penetration contained in an appropriate package. This allows L-ascorbic acid delivery into the skin and provides photo-protection against both UVB and UVA phototoxicity by a mechanism that is clearly not a sunscreen effect, but accomplished by neutralizing free radicals created by UV damage, as well as cigarette smoking and environmental pollutants.
This concept also applies to foods containing vitamin C and their retention of vitamin C activity. Fruit that is cut prematurely will often turn brown and wilt if left out in the air. When placed in air-tight containers and refrigerated, fruit appears fresher, longer. This temperature effect is important with most ingredients and has some relevance to all vitamin C products. That is, high temperatures increase oxidation of L-ascorbic acid and other ingredients.
Studies show that an L-ascorbic serum at a pH of 3.0 with a free acid concentration of 20% in a light-protected package maximizes biologic activity and penetration into the epidermis.6 Research also demonstrates that daily application produces an L-ascorbic acid concentration more than 20 times the normal levels after three consecutive days of application and maintains these levels with daily use.6 From a scientific standpoint, these levels are maintained for three days in the skin after the application of an appropriate vitamin C serum product is stopped.
It is important for clients to keep the lids of vitamin Cskin care products on properly as all are subject to oxidation over time. However, antioxidants such as vitamin C can begin oxidizing within minutes, while a peptide moisturizer may take months to oxidize. Remind clients not to leave the lids off their vitamin Cproducts any longer than necessary when applying, and look for products with airless or air-tight packaging that blocks out UVA and UVB light.
The Skin Care Ingredient Handbook is so much more than an ingredient dictionary. You will learn about cellular functions and skin aging; skin care trends for ethnic skin, scalp and hair products, BB creams, suncreens; active versus functional ingredients, natural, organic, and synthetic ingredients; OTC drugs; INCI names, antioxidants and DNA and how to read labels. Did we mention the newest ingredients are listed?
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