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On Choosing a Vitamin C Serum

On Choosing a Vitamin C Serum

Lots of knowledgeable skincare consumers are learning about the specific ingredients and formulations of various vitamin C products.  This is a terrific trend!  The more you know, the better choices you can make for your own particular needs. 

By now you know that Vitamin C has a host of beneficial properties for the skin (read our previous Journal entry here.)  

But there are lots of different chemical forms of vitamin C which function well under different conditions.  Lately we've seen a lot of discussion about which form of vitamin C is the most effective, and to what extent the pH of the serum factors into effectiveness. 

Time to get a little technical. 

The Basics of pH

You may recall from high school chemistry that pH is a measure of acidity/alkalinity, on a scale from 0-14.  

Water, at a pH of 7, is neutral - it is neither acidic nor alkaline.  Human skin is naturally slightly acidic, at a pH of 5.5. Soaps are often very alkaline, which is why they can be harsh on the skin.

There is a widespread belief that, in order to be effective and stable (potent even after exposure to light and air), Vitamin C products must have a pH of 3.5 or lower.  That's pretty acidic - like vinegar, as you can see on the chart.  Where did this belief come from, and is it universally true?  To answer that, let's get into.....

The Basics of Vitamin C

Pure Vitamin C extracted from natural sources is in a crystal form called L-ascorbic acid (LAA). LAA is water soluble but also very unstable once dissolved - meaning it oxidizes and loses potency by scavenging oxygen molecules from the air.  Anyone who has had a vitamin C product turn orange or brown knows what this looks like.  It's the same mechanism that makes a cut apple or potato turn brown after a few minutes exposed to air.

Other forms of vitamin C (vitamin C derivatives) have since been identified and incorporated into skin care products.  Some are water soluble like LAA, and some are fat soluble.  All have to be converted into ascorbic acid in the skin to make an impact on skin quality.  

Fat soluble C derivatives like ascorbyl palmitate and tetradecylhexyl ascorbate (yeah it's a mouthful - let's call it TP) do not have the oxidation problems that LAA has.  Because they are fat-soluble they are shown to penetrate deeper into the skin layers, which are themselves made of lipids (fats.)

Some other water-soluble forms, such as magnesium ascorbyl phosphate (MAP) and sodium ascorbyl phosphate (SAP), are more stable than LAA.  But what are we missing?  The question of which forms are effective in stimulating collagen production and other cell-level activity that we seek in effective skin care.

Research studies exist on all of these derivatives, though some are limited; moreover, the studies often compare their effectiveness to that of LAA.  As we get into that, let's remember that your choice of a Vitamin C product will be a function of several factors:

  • is the form of C proven to improve skin's quality?
  • is the concentration of C high enough to have an effect?
  • Is the pH of the product compatible with your skin?
  • Are there other ingredients that either enhance or inhibit the goals you want to achieve?

The Evolution of C Serums

Back in 1992, Dr. Sheldon Pinnell showed scientific evidence that LAA could stimulate the production of collagen in the skin.  That led to the development of an entire industry: Vitamin C products for skin care.  Dr. Pinnell was one of the pioneers of the industry, involved with the development of Cellex-C and SkinCeuticals.  

One of the best known C products on the market is SkinCeuticals CE Ferulic serum - which retails at $165 per ounce.  The formula for this product was patented - and that patent holds the first chapter of the pH-and-Vitamin-C story.

The CE Ferulic patent covered a specific mixture of active ingredients (15% LAA, 1% Vitamin E, 0.5% Ferulic Acid) at a specific pH: between 2.5 and 3.  Why this pH?  LAA is more stable in this highly acidic state, for one thing.  And so a general belief has evolved that Vitamin C serums must have pH under 3 or 3.5 to be effective.

But wait!

Some of the other water-soluble C derivatives are shown to convert to active forms in the skin, to stimulate collagen production and to control hyperpigmentation, but are stable at higher pH!  That means that with SAP (approx ph5) or MAP (approx pH7) you can have a serum that is effective without having to be at vinegar level pH.

The fat soluble C derivatives are also chemically stable at a neutral or skin-level pH.   

So how effective are all of these derivatives, and are they worthy of your skin care investment?  We're going to focus on two specific derivatives that seem to offer the best results in comparison to LAA: MAP and TP. We have referenced a few research papers below, and to cut to the chase:

- Fat soluble TP is shown to penetrate deeper into the skin than water soluble forms because the membranes and fluids between cells are lipid (fat) based.  This means the delivery of the active ingredient is closer to where you need it to perform.  It also converts at a high rate into active ascorbic acid once in the skin, and shows measurable improvement in the texture and appearance of skin.  It is shown to have a brightening effect due to the suppression of melanin production.  This is great for fading age spots, marks left after acne, etc.

- MAP also converts to ascorbic acid at a substantial rate, and is shown to penetrate to the depth necessary to have an effect on cell turnover and collagen stimulation.

- Here's the kicker - both of these forms are stable at a pH of 7 - neutral, same as water!  They do not break down or oxidize upon exposure to air and light the way that LAA does.  

- There are studies showing modest effectiveness of the other C derivatives mentioned above, but none comparable to LAA, TP or MAP.  For the sake of brevity we will leave further research on those to the reader.

Wrapping Up

So now we know that the belief that a C serum must be at a very low pH is a holdover from the Skinceuticals patent.  We also know that it applies to the LAA form of vitamin C - not to all forms.  And we know, from experience, that even at a low pH, LAA serums are quick to oxidize.

Here's why it should matter to you: 

- Irritation

Some people are not able to tolerate the very acidic LAA serums.  Their skin becomes irritated, seems dry or flaky, and can even break out from pure unhappiness.  If you can tolerate the low pH serums, you must be careful when layering them with other products.  If the pH levels aren't the same, the effectiveness of one or more of the products can be inhibited.

With a neutral or close to neutral pH, you don't have to worry about interference with other products.  A neutral pH will also be gentler on the skin.  

- Effectiveness

LAA is very effective at stimulating collagen and having a brightening effect on skin.  TP and MAP are shown to be super effective at brightening, stimulating collagen production and protecting from sun damage.  All three are effective options when choosing a C serum.

- Shelf life

Here's the rub - if you're ok with storing your bottle in the fridge and decanting it a little at a time, a water-based LAA serum can be a good choice.  But oxidation is a common and disappointing outcome - and who wants to pour their products down the drain?  Some LAA serums seem to be more stable than others.  Some tips on choosing follow.

The Bottom Line

When choosing a C serum you are not limited to either LAA or low pH to get results!

  1. A non-aqueous LAA serum (oil, alcohol or other carrier) will not have the same oxidation problems as a water-based one. Looking for one of those might be a good choice.
  2. Micro-encapsulation of the vitamin C is a technique that can increase the shelf life of a water-based C serum - so that's a feature to look for as well.
  3. A serum that uses MAP, TP or a combination of the two is highly effective at a pH levels that are gentler on the skin.
  4. You have lots of choices - pick what works for you.

One last thing: look for a C serum in a pump bottle - it will stay fresh longer and be easier to use. We still don’t get why so many C serums come in dropper bottles!

Our Radiance Repair serum blends oligopeptide-68, a proven pigmentation control peptide, with hyaluronic acid, aloe and both micro-encapsulated MAP and lipid-soluble TP at a neutral pH.  For effective, non-irritating skin brightening. 

All the benefits of vitamin C in a soothing and hydrating formula.  Try it now.


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* Studies have shown that LAA must be in a concentration of at least 10% and up to 20% to have a significant effect on the quality of skin.  

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Comments on this post (1)

  • Nov 26, 2018

    Hi you mentioned that the dropper isn’t as good as a pump bottle , yet ….. the vitamin C serum is a dropped . I’m confused.

    — Raisha

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