The dirty truth about vitamin C

I’m sure you have heard about vitamin C. This active has invaded the beauty world. But do you know really what it is and what do we know about it? 

What is vitamin C? 

The scientific name for vitamin C is ascorbic acid. If synthesize in a laboratory ascorbic acid exist in two forms L (levogyre) and D (dextrogyre). Our cells cannot use the D-ascorbic acid which is why it is important that brands specify the vitamin C they use. L-ascorbic acid seems to be the most abundant antioxidant in the skin. The epidermal cells (keratinocytes) are very efficient at capting vitamin C. 

If applied on the skin only a solution between 5 to 20% of L-ascorbic acid at pH 3.2 or lower can penetrate the skin. Furthermore, a daily application of 15% L-ascorbic acid at pH 3.2 increases skin L-ascorbic acid levels 20-fold and the skin is saturated for 3 days. Unfortunately, those studies were done in porcine skin and not on us. 

This being said in Human it was shown that L-ascorbic acid blocks enzymes responsible for collagen degradation and an increase of the mRNA for collagen.

L-ascorbic acid displays a photoprotection against a sunburn. My interpretation is that L-ascorbic acid helps the cells to cope with the damage.

Taken together, L-ascorbic is a safe bet and probably one of the best antioxidants for the skin so far. 

What else does it do?

Besides being an antioxidant it is also anti-inflammatory by shutting done inflammatory cytokines (= stress signals) in the skin.

In vitro studies suggest that it promotes collagen synthesis. One in vivo study could confirm it. A lot still needs to be done to demonstrate it. Finally, ascorbic acid is an excellent skin brightening ingredient. 

The con: instability

L-ascorbic acid is very unstable in solution and will oxidize in the presence of oxygen. It oxidizes quickly because it is an excellent antioxidant. Keep it tightly close and in the fridge.

The marketing lie 

I no longer count the numbers of product claiming they used vitamin C even though they don’t. They use derivatives. Some derivatives are interesting but there are not vitamin C and are likely less efficient. 

Vitamin C derivatives: 

Here are some derivatives


It doesn’t seem to be converted into L-ascorbic acid but seems to be an antioxidant.  

Ascorbyl 2-phosphates

It is either formulated with magnesium or sodium. They are likely not efficient and are not antioxidants because of their molecular structure. They need to be converted into L ascorbic acid but are poorly absorbed or not at all. This one is a pass. 

Ascorbyl 2-glucoside

It can be transformed into L-ascorbic acid in vivo by an enzyme (alpha glucosinase) and it penetrates the skin but its efficacy is unknown. It is a skin brightener. 

Tetra-isopalmitoyl ascorbate or Ascorbyl Tetraisopalmitate

The most promising derivatives. In reconstituted skin models, it penetrates the skin and is converted into L AA and has antioxidant properties: it protects the skin after sun exposure. It is a skin brightener. 

3-O-ethyl ascorbic acid

There is almost nothing about it. It has a skin brightener though. 

🍊L-ascorbic acid

🍋 Derivatives 

  • The ordinary Glucoside 12%⎪
  • The Ordinary Ascorbyl Tetraisopalmitate 20%⎪

Thank you for your time. 



PMID: 23174055

PMID: 11207686 

I only put the two most relevant. 

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