Dr Ian Webster
Dr Ian Webster

Types of Vitamin C

There are many types of Vitamin C and while they all offer antioxidant protection and anti-ageing benefits, there are differences between them: whether they are pure or esterified derivatives and also their formulation, concentration, permeability and efficacy when used topically as a cream or serum on the skin. It is very important to choose the correct form of Vitamin C as they can vary in effectiveness, stability and tolerance levels.

Benefits of Vitamin C

  • Assists in the formation of new collagen to restore healthy protein fibres
  • Provides antioxidant protection against environmental damage by defending the skin from free radical activity which causes photo-ageing.
  • Shields the skin from aging and DNA damage caused by pollution
  • Promotes skin repair and wound healing
  • Brightens the skin and reduces uneven skin tone
  • Improves hyperpigmentation by regulating melanocyte functioning
  • Reduces redness (erythema) and has anti-inflammatory benefits
  • Improves hydration levels
  • Promotes a youthful, healthy skin

Vitamin C products are generally formulated as serums but recently encapsulated, anhydrous formulations have been introduced into the market.

L-Ascorbic Acid

L-Ascorbic Acid is seen as the gold standard when it comes to Vitamin C because it is the purest form and it is multi-functional with its ability to protect, prevent and correct the skin when applied topically. In the past, it has been much maligned as being unstable but this is only true if it is not formulated correctly.

It’s a potent antioxidant that offers both internal and external protection, if formulated correctly, its most defining features are its bioavailability (recognized by the skin) and its permeability – having the ability to penetrate directly into the dermis to stimulate collagen synthesis. Generally, esterified forms of Vitamin C first have to be converted to ascorbic acid in the cells before they can help to stimulate new collagen.

Besides its ability to enhance collagen production, L-Ascorbic Acid, when topically applied, has been shown to down-regulate the enzymes responsible for collagen degradation and to preserve existing collagen. It has been shown to be very effective in preventing and treating sun-damaged skin.

The formulation is everything when it comes to L-Ascorbic Acid, for this water-soluble form of Vitamin C to penetrate the skin and be bioavailable, it should be formulated at the correct acidic pH. For optimized penetration into the skin, it should be within 2.0- 3.5 pH range.

For meaningful levels to be delivered into the skin L-Ascorbic Acid should be at concentrations of between 10%-20%. Studies have shown that a daily application of 15% L-Ascorbic Acid, at a pH of 3.2, increased skin L-Ascorbic Acid levels 20-fold and tissue levels were saturated after 3 days.

For optimized penetration into the skin, L-Ascorbic Acid should be within 2.0- 3.5 pH range.

L-Ascorbic Acid can be irritating to the skin, so it should always be introduced at a lower percentage and stepped up according to your own skin’s tolerance levels. The higher the concentration and the lower the pH, the more risk of irritation especially if your skin is sensitive or prone to rosacea. It is always sad to hear people say they are ‘allergic’ to Vitamin C but this is usually attributed to using the incorrect form or strength, or that it has been introduced it to the skin too rapidly without building tolerance.

L-Ascorbic Acid is vulnerable to light and heat and if not stored correctly it can oxidize rapidly. It should always be packaged in dark, opaque container and exposure to air should be limited. It should be stored in a dark, cool, dry place, away from any form of sunlight or heat which can both degrade the product.

It should always be packaged in dark, opaque container and exposure to air should be limited.

Everyone needs a buddy, research has proven that specific combinations of antioxidants, when effectively formulated, perform synergistically and provide far more superior results than single antioxidant formulations. A good example is Vitamin E, a potent lipid-soluble antioxidant, which has been proven to increase the photoprotection effects of L-Ascorbic Acid. In turn, L-Ascorbic acid also helps to regenerate the oxidative form of Vitamin E, that is important for preventing oxidative damage in the lipid cell membrane. Research has shown that Ferulic Acid aids in both stabilization of the L-Ascorbic molecule and achieving an acidity of a pH below 3.5.

Derivative Forms of Vitamin C

Magnesium Ascorbyl Phosphate (MAP)

Magnesium Ascorbyl Phosphate is a non-irritating, stable, ascorbyl ester of Vitamin C. This lipophilic molecule is easily absorbed into the skin, has hydrating effects and helps to decrease transepidermal water loss. It is a free radical scavenger, it helps to improve skin elasticity, boosts collagen synthesis and helps to reduce photodamage. It also promotes wound healing and suppresses melanin formation at significantly lower concentrations than L-Ascorbic Acid.

This would be a better choice for those with more sensitive skins, as it is not formulated in such a low acidic form that it causes irritation in more sensitive skins.

Sodium Ascorbyl Phosphate (SAP)

Sodium Ascorbyl Phosphate is a salt of Ascorbic Acid (Vitamin C), which provides antioxidant protection.  It has also been shown in some studies that 1% SAP has a strong microbial effect in reducing which P.acnes, as well as sebum oxidation and this form of Vitamin C, could be used as a co-treatment with other acne treatments.

Tetrahexyldecyl Ascorbate (THDA)

Tetrahexyldecyl Ascorbate is a stable, oil-soluble form of Vitamin C used in skincare products and sunscreens. It works well when used together with other forms of Vitamin C in anti-ageing products. There is some discussion around whether it is more potent than L-Ascorbic Acid, because it is oil-soluble and able to penetrate the lipid layer into the dermis. However, studies show that if L-Ascorbic acid is correctly formulated according to strict parameters it is equally able to penetrate into the dermis.Other Common Esters or Derivates of Vitamin C:

  • Ascorbyl Palmitate
  • Ascorbyl Silanol
  • Sodium Ascorbate
  • Ascorbyl Glucoside
  • Ascorbyl Glucosamine
  • Ascorbyl Methylsilanol Pectinate

Topical Vitamin C is a much discussed and studied topic, with a diverse array of opinions as to the best form and this can be confusing. I feel that correctly formulated, stable, L-Ascorbic Acid is generally the first choice when it comes to choosing Vitamin C.  Other stable, esterified forms of Vitamin C, especially the lipid soluble types, can be more gentle on the skin so they should not be discounted for those with a sensitive skin. A combination of L-Ascorbic Acid with Vitamin C esters can also be very effective.

It important to note that the human skin has low permeability and any Vitamin C, in whatever form, must be able to penetrate the skin’s outer layer, the stratum corneum, for delivery into the dermis where collagen synthesis can take place. Only then will meaningful changes take place skin.

Reference: Dermatol Surg 31:7 Part 2: July 2005

Posted in NEWS / Ingredient Focus on June 7th, 2018.

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