Cleveland Clinic: The Authority

L-ascorbic acid

This is the only form of vitamin C that you should look for in your skin care products. There are many skin care products on the market today that boast vitamin C derivatives as an ingredient (magnesium ascorbyl phosphate or ascorbyl palmitate, for example), but L-ascorbic acid is the only useful form of vitamin C in skin care products. With age and sun exposure, collagen synthesis in the skin decreases, leading to wrinkles. Vitamin C is the only antioxidant proven to stimulate the synthesis of collagen, minimizing fine lines, scars, and wrinkles. Data suggests that L-ascorbic acid may better the appearance of photodamaged skin. Initial use of vitamin C containing creams can cause stinging or redness, but these side effects generally go away with continued use.

By Sheldon R. Pinnell, MD, Doren L. Madey, PhD

Aesthetic Surgery Journal

Ascorbic Acid Derivatives

Vitamin C is L-ascorbic acid; this is the molecule that the body uses. Because it is inherently unstable (thereby allowing it to be so effective as an antioxidant), more stable derivatives of ascorbic acid have been substituted in cosmetic formulations. For these derivatives to function, they must first be absorbed into skin and then converted to L-ascorbic acid. Common derivatives include magnesium ascorbyl phosphate and ascorbyl-6-palmitate. Because magnesium ascorbyl phosphate is a charged molecule, it penetrates skin poorly. Ascorbyl-6-palmitate is lipophilic and may prefer the environment of a cream base to skin. Because percutaneous absorption data have not been published for ascorbyl-6-palmitate preparations, it is not clear whether they absorb into skin. However, skin fibroblast studies reveal that this derivative behaves differently from L-ascorbic acid and is toxic at physiological levels (100 μmol/L).

Effective Topical Vitamin C Products

For a topical vitamin C formulation to work, it must first penetrate skin and then remain stable and be available in high enough concentrations to have a biologic effect. Research to date indicates that the gold standard is stable L-ascorbic acid at high concentration (more than 10%) and low pH (<3.5).

Clinical Studies

Topical vitamin C is used for its photoprotective and anti-inflammatory effects. Because L-ascorbic acid is essential for collagen synthesis, it is also used for its wound healing effects. In photoaged skin, anecdotal improvement has been reported; physicians and their patients particularly note improved skin clarity and color. The results of such observations are encouraging; double-blind studies are underway.