I’ve been working with many forms of Vitamin C over the years. Topical C is preferred over internal, dietary C in skincare as the bioavailability of Vitamin C in the skin is inadequate when ingested orally (1). Vitamin C is the most abundant antioxidant in the skin and extremely important in our skin health and slowing skin aging. I’ve worked with multiple plants that contain considerable concentrations of C but in product development, I wanted to offer a clinical concentration of C in a product, so I formulated with various forms from plant sources to pure, lab synthesized L Ascorbic Acid to its stabilized derivatives like Sodium Ascorbyl Phosphate and Textrahexyldecyl Ascorbate.
Hopefully, this blog will help people navigate Vitamin C in skincare and bring clarity to why plant-sourced Vitamin C in skincare is limited, and why Vitamin C in skincare needs the lab synthesized form to achieve the specific, efficacious results shown in studies. I’m hoping to clear up some of the confusion in the green beauty market.
Let’s start with what Vitamin C is. L-ascorbic acid (LAA) is the chemically active form of Vitamin C. In nature, Vitamin C is found in equal parts as LAA and D-ascorbic acid. These are essentially isomeric molecules and are mutually interchangeable. However, only LAA is biologically active and thus useful in medical practice (3). Vitamin C forms a part of the complex group of enzymatic and non-enzymatic antioxidants that co-exist to protect the skin from free radicals. It neutralizes the oxidative stress by a process of electron transfer. Free radicals are highly toxic, unstable molecules that can cause damage to nucleic acids, proteins, and cell membranes, degrade collagen, reduce collagen production, and increase elastin accumulation(4). This leads to the clinical manifestations of photoaging pigmentation, telangiectasias, coarse texture, deep wrinkles, and solar elastosis.
Vitamin C has been shown to protect collagen and is essential for collagen synthesis (5). Vitamin C is available in a number of active forms. Among all forms, L-ascorbic acid is the most biologically active and well studied (6). L-ascorbic acid is a hydrophilic and unstable molecule, hence the poor penetration into the skin because of the hydrophobic character of the stratum corneum (7). Reducing the acidity of L-ascorbic acid to a pH below 3.5 is an effective method of improving its stability and permeability. It’s notoriously difficult to formulate with as it is extremely unstable when exposed to light or oxygen. Pure LAA and requires a low pH for percutaneous absorption. If the pH isn’t between 2.5-3.5 the LAA can remain on the surface of the skin, oxidize and react with other products. This low pH causes skin sensitivity as well even with effective penetration. If a cosmetic product with LAA has been poorly formulated and is destabilized when applied to the skin, the free radicles and acidic by-products left on the acid mantle can end up damaging skin and accelerating skin aging along with reacting with other products layered after.
Hibiscus extract, for example, contains a high amount of Ascorbic Acid/Vitamin C for a plant, at a total concentration of 0.05 - 0.1% (8). Yes, the Ascorbic Acid content of hibiscus contributes to its free radical scavenging ability in the skin - but that’s not nearly enough C to compare that concentration to the 8-20% concentration of lab synthesized LAA and its derivatives to match the results they’ve been shown to deliver in clinical trials and studies. The highest natural source of Vitamin C is found in Kakadu plum. At 100% concentration, the pure, cosmetic grade, 3:1 extract of Kakadu plum yields an overall 2% concentration of Vitamin C. There isn’t a natural source of vitamin C in cosmetics available higher than Kakadu Plum - and the total concentration of C in Kakadu extract is only 2%. And the formulation still needs several other ingredients to create a wearable product that can effectively penetrate the surface of the skin. Let's say the Kakadu was formulated at a 30% concentration in a formula - with this formula, a 2% concentration of C in the 30% used, the end product will contain less than 1% Vitamin C in the formula. Yes, that .07% Vitamin C is still beneficial to the skin - but again, that’s not nearly a high enough concentration of C to deliver the results that studies confirm C can offer. There’s no way to fit 8+% whole plant C in a bottle of skincare. Plants high in Vitamin C offer incredible bioactive, multi-nutrient support - but you can’t fit the amount of plant matter necessary to reach the percentage of C in a jar to make the dermal impact in the way concentrated lab synthesized C has been proven to work. At best, a whole plant Vitamin C product will only contain a fraction of Vitamin C we require for our skin health.
Do not compare internal vitamin supplementation/RDA with the topical, cosmetic concentration - it’s not the same. Many herbs and plants contain Vitamin C, several of which have a high concentration relating to internal daily nutritional value. This daily value internally does not directly translate to percentages of C that have been shown to deliver clinical results topically. For instance, the 900% Recommended Daily Value of Vitamin C in 1/2 cup Acerola Cherries ingested does not mean Acerola Cherries smashed up or extracted and applied to the skin will give you an appropriate, high, clinical concentration of Vitamin C necessary for the results Vitamin C has been shown to deliver. Yes, Acerola Cherries are very high in Vitamin C but this does not mean a high clinical concentration of Vitamin C is delivered when applied topically.
With the studies showing how difficult L-Ascorbic Acid is to deliver into the dermis, research has turned towards finding more stable forms of Vitamin C. Derivatives of Vitamin C were created to stabilize the molecule and enhance penetration and formulation ease at a healthy skin pH. The most stable type of Vitamin C was discovered - Tetrahexyldecyl ascorbate is a stable, fat-soluble form of Vitamin C. This derivative of vitamin C is excellent for skin penetration because of its fatty acid component helps aid penetration. It also pairs very well with retinol for enhanced effectiveness. Unlike the water-soluble L-Ascorbic Acid, Tetrahexyldecyl Ascorbate is oil soluble. Studies have shown that Tetrahexyldecyl Ascorbate is a more stable, less irritating, longer-lasting, and a deeply penetrating form of Vitamin C. Clinical studies show that this form is three times more penetrating than L-Ascorbic Acid. It lasts longer within the skin and promotes up to 50% more collagen production. The enhanced penetration of this oil-soluble Vitamin C also means that you do not need a high percentage of in the formulation (9,10,11).
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- J Clin Aesthetic Dermatol 2017 July;10(7):14-17
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- Eggensperger and Wilker 1996
- Clinics in Plastic Surgery, July 2016, page 601
- Journal of the American Academy of Dermatology, Supplement, May 2014, pages AB26
- Dermatologic Surgery, March 2002, pages 231-236
Double-Blind, Half Face Study Using LAA and Tetrahexyldecyl Ascorbate
OBJECTIVE: The objective of this study is to determine if the topical use of a Vitamin C preparation can stimulate the skin to repair photodamage and result in clinically visible differences, as well as microscopically visible improvement.
METHODS: Ten patients applied in a double-blind manner a newly formulated vitamin C complex having 10% ascorbic acid (water-soluble) and 7% tetrahexyldecyl ascorbate (lipid-soluble) in an anhydrous polysilicon gel base to one-half of the face and the inactive polysilicon gel base to the opposite side. Clinical evaluation of wrinkling, pigmentation, inflammation, and hydration was performed prior to the study and at weeks 4, 8, and 12. Two mm punch biopsies of the lateral cheeks were performed at 12 weeks in four patients and stained with hematoxylin and eosin, as well as in situ hybridization studies using an anti-sense probe for mRNA for type I collagen. A questionnaire was also completed by each patient.
RESULTS: A statistically significant improvement of the vitamin C-treated side was seen in the decreased photoaging scores of the cheeks and the perioral area. The peri-orbital area improved bilaterally, probably indicating improved hydration. The overall facial improvement of the vitamin C side was statistically significant. Biopsies showed increased Grenz zone collagen, as well as increased staining for mRNA for type I collagen. No patients were found to have any evidence of inflammation. Hydration was improved bilaterally. Four patients felt that the vitamin C-treated side improved unilaterally. No patient felt the placebo side showed unilateral improvement.
CONCLUSION: This formulation of vitamin C results in clinically visible and statistically significant improvement in wrinkling when used topically for 12 weeks. This clinical improvement correlates with biopsy evidence of new collagen formation.
Fitzpatrick. Rostan. Dermatol Surg. 2002 Mar;28(3):231-6.