Along with retinol, vitamin C has long been heralded by dermatologists as a gold standard of beauty ingredients. But you probably already knew that, because research has consistently re-affirmed what we’ve known for years: that vitamin C can help diminish dark spots, brighten complexions, and drum up collagen production when it travels to layers of the dermis. For the most part, we also know that “our skin does not produce vitamin C, therefore it is very important to supplement it in topical skin care,” notes Jeannette Graf, MD, a New York-based dermatologist.
But all that knowledge doesn't do us much good if we aren't sure of the best way to harness vitamin C's powers. Historically, the ingredient has been notoriously tricky to stabilize in topical products. Like vampires, vitamin C loses stability and potency when in contact with air, light, and water (the basis of most skin-care products) — which makes it extremely tricky to work into a serum or mask. “Because vitamin C is so unstable in the presence of light, extremes in pH, and temperature, products that contain it are specially formulated,” says New York-based dermatologist Joshua Zeichner, MD. In other words, not all C-based skin care is created equal. Adds Dr. Graf, “The most important part of topical vitamin C is what type of vitamin C it is, since it must be stable in order for it to be of value.”
The good news? Scientists and cosmetic chemists have been working to overcome these obstacles for years. And the latest vitamin C-based skin care is some of the best to market yet. Among such solutions? Water-free formulations, a favorite of Dr. Graf’s. “A water-free system helps ensure the long-term stability of topical vitamin C," she says.
Also in the mix: cold-pressing techniques which eschew typical heat methods used to extract ingredients and result in better stabilization; powder and pearl encapsulation, also geared to help extend stability; time-released products; and concentrated formulas that shoot up into 30% potency, something that may be useful to nicotine addicts. “My feeling is that 10-20% vitamin C used daily in the morning and in the evening is quite good,” Dr. Graf says, adding, "Cigarette smokers lose more vitamin C than non-smokers. So smoking is terrible for many reasons, but if someone is unable to stop smoking, they should use an even higher concentration of 20 to 25% vitamin C.”
Finally, though there are several types of vitamin C found in product ingredient lists (including magnesium ascorbyl phosphate, tetrahexyldecyl ascorbate, ascorbyl palmitate, ascorbyl glucosamine, and ascorbyl tetraisopalmitate), it’s actually L-ascorbic acid that trumps ‘em all, according to our pros. “L-ascorbic acid is the only form of vitamin C which is recognized by the skin,” Dr. Graf says. “Whichever form of stabilized vitamin C is used, they must bio-convert to L-ascorbic acid before the body can use it.” The good news? More and more formulations are using it as their C-source.