Vitamin C is the most common antioxidant in the skin. Unfortunately, humans do not have the enzyme (L-gluconogamma lactone oxidase) to make vitamin C, therefore it must be obtained from external sources.
Vitamin C (ascorbic acid) is a molecule that has been shown to keep your skin healthy and vibrant thanks to its antioxidant properties and role in stimulating collagen synthesis.
The nutrient is naturally found in the skin’s epidermis (uppermost) and dermis (middle) layers. Like many other substances like collagen and hyaluronic acid, vitamin C declines with age. Its quantity can also be more quickly depleted by pollution, sun exposure, and lifestyle habits like cigarette smoking.
L-ascorbic acid is the active form of vitamin C that carries out the biological effects. Besides retinoids, vitamin C is probably the next most studied ingredient in skincare. Ascorbic acid has many benefits. Repeat studies have shown it helps to prevent photodamage from UVA and UVB radiation. It stimulates collagen production, serving as a co-factor for enzymes in collagen production. Lastly, vitamin C is a great lightening ingredient. It blocks tyrosinase, a key enzyme in melanin production.
However, vitamin C is highly unstable. It easily oxidizes in light, heat, pH change, and the presence of other ions. This has led to the development of various vitamin C derivatives that are more stable while trying to retain efficacy. However, formulation continues to be a challenge. Demonstrating ingredient effectiveness needs to occur not just in the laboratory setting or on animals, it also needs assessment on human skin.
Unfortunately, there’s a paucity of data regarding skincare ingredients in general (compared to medical dermatology), and some publications are conflicting. One study may show the benefit of a derivative, while another demonstrates no efficacy. This inherently speaks to the challenges of manufacturing L ascorbic acid, as the formulation is everything.
References
Pinnell, Sheldon R., et al. “Topical L-Ascorbic Acid: Percutaneous Absorption Studies.” Dermatologic Surgery, vol. 27, no. 2, 2001, pp. 137–142.
Stamford, Nicholas P J. “Stability, Transdermal Penetration, and Cutaneous Effects of Ascorbic Acid and Its Derivatives.” Journal of Cosmetic Dermatology, vol. 11, no. 4, 2012, pp. 310–317.
“Ferulic Acid Stabilizes a Topical Solution Containing Vitamins C and E and Doubles Its Photoprotection for Skin.” Journal of the American Academy of Dermatology, vol. 52, no. 3, 2005.
Lin, Jing-Yi, et al. “UV Photoprotection by Combination Topical Antioxidants Vitamin C and Vitamin E.” Journal of the American Academy of Dermatology, vol. 48, no. 6, 2003, pp. 866–874.
Stamford et al. “Stability, transdermal penetration, and cutaneous effects of ascorbic acid and its derivatives.” Journal of Cosmetic Dermatology. vol. 11, 2012. pp: 310–317.