We know that Vitamin C is a dietary necessity for health and immunity. However, Vitamin C plays a very important role in preventing and correcting skin damage when applied topically on a daily basis. It is well-known in skin care to be one of the most important components of a successful anti-aging plan.

While there are other must-haves in a lifelong skin care regimen, adding l-ascorbic acid to your current regimen will yield noticeable improvements in as little as 6 weeks. Personally I have been using Retin-A for acne since the age of 14 and will likely never stop unless I’m trying another retinoid. Several years ago while working in the office of a Plastic Surgeon I started using SkinCeuticals CE Ferulic Serum every day. Within mere weeks I saw a very unexpected and noticeable improvement in the overall clarity, texture and appearance of my skin. I was excited by the prospect of not only improving my skin but being able to provide the same improvement for my clients.

Since then through reading countless clinical studies I have learned that antioxidants prevent more damage from occurring in the skin while retinoids, glycolic acids, salicylic acids, brightening agents and countless other ingredients work to correct damage. If we can inhibit the amount of damage taking place due to oxidation, other products and treatments yield better results. JAAD Sept 2008

Because Vitamin C is so important to skin health, many skin care brands have created their own variations of this very important antioxidant. Many of these formulas contain different forms of Vitamin C while all making very similar claims regarding efficacy and results.

How can so many different forms of Vitamin C yield the same end result for the skin? If the skin uses l-ascorbic acid for protection and stimulation of collagen and further, cannot convert other forms of Vitamin C to l-ascorbic acid, is it possible to see similar results with vastly different formulas?

To briefly revisit why the skin needs antioxidants:

We are born with youthful skin that begins to show the signs of environmental damage in the form of fine lines, wrinkles, sagging and brown spots over the years. We also experience a slow down of the rate at which our skin cells renew themselves which again contributes to the changes we see on our skin. But exactly what causes those changes? Oxidation. Whether it’s UV, Infrared heat, Smoking, Pollution and even Ozone, the environment in which we live each day causes oxidation by producing free radicals in the skin. What is a free radical? Simply stated, a free radical is an unstable oxygen molecule seeking an electron to stabilize the molecule. It finds that electron by “stealing” it from another stable oxygen molecule. The process repeats itself countless times in the skin creating a cascade effect that destroys collagen, causes hyperpigmentation and largely contributes to the aging we see on our skin.

Antioxidants work to stop that oxidative process by “donating” an electron to the unstable oxygen molecule (free radical). By stopping this thievery in the skin, we stop the destruction of healthy collagen while also helping the skin to better protect and repair itself against free radical damage. Not only will your antioxidant protect you today but daily use will provide you continued improvement in your skin for as long as you use it.

Why Vitamin C?

While there are many antioxidant ingredients available for both oral use and topical application, very few of them have significance when applied topically to the skin. It is imperative that we apply an antioxidant daily as only 8% of the antioxidants ingested orally have a positive effect on the epidermis. Many clinical studies have proven that Vitamin C is the single most important antioxidant the skin uses (in the form of l-ascorbic acid) to protect against collagen degradation and stimulate repair. J Derm Science 1996 Further, when the skin is exposed to environmental damage or even laser treatments, l-ascorbic acid levels in the skin are lowered by the exposure at the very time when the skin needs it the most. Replenishing l-ascorbic acid enhances the skin’s protective and healing capabilities.

There are some basic parameters that must be met in order to formulate an effective Vitamin C based antioxidant. The formulation must contain l-ascorbic acid in a concentration of 10%-20% at a pH of less than 3.5 These parameters were proven and published in this well-known clinical article J Dermatol Surg Feb 2001

Knowing that l-ascorbic acid must be formulated at a low pH for optimal penetration, then the formulation must be in an aqueous solution. Why? Because only a water-based solution can host and maintain the acidic pH required for stabilization and penetration of l-ascorbic acid. That means that a Vitamin C cream, lotion or emulsion is either not formulated with l-ascorbic acid or if it does utilize l-ascorbic acid, the pH is too high for optimal bioavailability.

Based on water-soluble vs lipid-soluble, I categorize the Vitamin C forms accordingly:

WATER SOLUBLE FORMS OF VITAMIN C:

l-ascorbic acid (ascorbic acid) – Well known and respected as the most valuable form of Vitamin C for skin because the skin contains l-ascorbic acid and specifically uses this form of Vitamin C to protect and repair itself from damage. Because the skin contains and uses l-ascorbic acid, it immediately recognizes and uses it readily without the need to convert it to any other form of Vitamin C – 100% bioavailability in the skin. Other forms of Vitamin C need to convert to l-asorbic acid in the skin. However, the skin can’t efficiently convert other forms of Vitamin C to AA, therefore, bioavailability is greatly reduced with other derivatives.

Other derivatives are not wholly without value as they do show some improvements on the surface of the skin in brightening, clarity and hydration. However the reduced bioavailability of derivatives means that they may provide only superficial changes rather than improving the health of the skin long-term.

Sodium Ascorbic Phosphate (SAP)– a form of Vitamin C touted as a precursor to l-ascorbic acid. It is a gentler form of Vitamin C that has demonstrated some success in improving acne scarring and controlling acne bacteria on the skin. To date, there is limited clinical evidence regarding the use of SAP in skin care outside of improving various aspects of acne. Int J Cosmet Sci Jun 2005

Magnesium Ascorbic Phosphate (MAP) – another water-soluble form of Vitamin C. MAP is stable at a higher pH than l-ascorbic acid which can make it preferable for very sensitive skin. It is also proven effective in inhibiting the formation of excess melanin at a concentration of 10%. It does have the ability to be absorbed and to convert to AA once in the skin. Aging Research News 2007 However, as the skin cannot efficiently convert MAP to AA, the bioavailability of Vitamin C in the skin when using MAP would be lower than when using AA.

LIPID SOLUBLE FORMS OF VITAMIN C:

Tetrahexyldecyl Ascorbate (TA)/Ascorbyl Tetraisopalmitate (ATIP) –A molecule derived from vitamin C and isopalmitic acid with the goal of stabilizing Vitamin C for better delivery into the skin for ultimate conversion to l-ascorbic acid.

This Vitamin C derivative is one of my least favorite because the products that formulate with it do so claiming that it is more stable than l-ascorbic acid. However, stability is not the only determinant of a valuable Vitamin C nor does it guarantee penetration or conversion to l-ascorbic acid in the skin.

The manufacturer/supplier claims that l-ascorbic acid only reaches the water-soluble cell membranes in the skin, thereby leaving lipid-soluble cell structures unprotected. The claim with TA is that protects the lipid-based cells and is therefore more valuable to the skin.

However, in the study upon which this claim is based, the product studied was a combination of 7% TA and 10% AA. Those study participants did see statistically significant improvements in visible photoaging and increased collagen production. The study authors assert that the AA in this formula acts as a protective antioxidant while also claiming that the TA acts as both antioxidant and collagen stimulator. Dermatol Surg Mar 2002

Curiously, the same improvements have been associated with AA in numerous published studies dating back many years, so the design of this study makes the conclusion less than a stellar case for TA. Given that the manufacturer was seeking to prove the value of TA alone, the study should have only involved TA with measured results. Perhaps the result with TA alone would have been less than impressive which is why they chose to include the very reliable and well-studied AA. 

Ascorbyl Palmitate

A Vitamin C ester created by combining ascorbic acid with palmitic acid to create a lipid-soluble form of Vitamin C. Due to the lipophilic nature, penetration may be greatly reduced as it may not absorb past the stratum corneum. Further, the concentrations necessary to affect collagen stimulation would be very high making formulation a concern. Evidence also exists which indicates that AP promotes undesirable lipid peroxidation and cytotoxicity in keratinocytes when it is applied to skin and exposed to UVB thus having a negative impact for the skin. J Invest Dermatol Nov 2002

I would not recommend antioxidant products that only utilize lipid-soluble forms of Vitamin C as they have very limited absorption which results in lower likelihood of conversion to l-ascorbic and reduced bioavailability. If you are concerned about protecting lipid-soluble tissues in the skin, Vitamin E (Alpha Tocopherol) is proven far more effective and also has a synergistic relationship with l-ascorbic acid. Arch Biochem Biophys Jan 1998

MORE IS NOT MORE

If a little is good, a LOT is great, right? Not in this case! One study showed that the skin actually maintains more l-ascorbic acid when a solution of 20% or less is applied vs a solution of 25% or higher. Something happens above the 20% wherein the level of l-ascorbic acid in the skin decreases to far less than 20%. One hallmark study demonstrated that the skin has a maximum level that it can maintain and that anything over 20% is not beneficial. Dermatol Surg Feb 2001

pH DOES MATTER

Though l-ascorbic acid has a small enough molecular weight to enter the epidermis, by lowering the pH to a range of 2.5-3.5, penetration is optimized. A pH below 2.5 can be irritating while a pH above 3.5 is less effective. Dermatol Surg Feb 2001

FOR OPTIMAL RESULTS, CHOOSE L-ASCORBIC ACID

Though MAP can improve surface clarity and SAP might improve superficial acne scars, l-ascorbic acid is what the skin contains and uses for repair, so why use another less effective derivative?

Taking this into consideration when choosing a daily antioxidant, look for a formula that contains l-ascorbic acid (also listed as ascorbic acid) in a concentration of between 10% and 20% at a pH of 2.5-3.5. 

KEEP IT SIMPLE

Look for formulas with very short ingredient lists and no silicones. Remember that l-ascorbic acid must be formulated in an aqueous base, so other ingredients that won’t sit in an aqueous base won’t mix well. Further, other ingredients might require a vastly different pH for stability and efficacy which could necessitate changing the pH of the formula to one that is too high for  optimal efficacy of l-ascorbic acid.

Next week – l-ascorbic acid combined with other treatment modalities