demystifying skincare with science

When it comes to the proven skincare ingredients, Vitamin C usually makes the top 5 after “gold standards” like sunscreen and retinoids. However, like Vitamin A in skincare, Vitamin C can come in many forms – some more effective than others. It’s also not the most stable ingredient and difficult to get into the skin. In this overview, we will cover what this ingredient is, what it does for the skin, and how to look for products that are actually going to be effective.

If you haven’t already, make sure to watch my YouTube video on this topic where I also review on my favorite Vitamin C serums and which skin types and concerns I suggest them for.

Some links and codes may be affiliate. They add no cost to you, the reader, but help support the author and her content.

Vitamin C

Vitamin C is a water-soluble vitamin and essential for human health. Because we’re unable to synthesize it in our own bodies, it must be consumed through diet. As a powerful reducing agent in redox reactions, it serves as a cofactor for many key enzymatic reactions – including collagen synthesis. This is also what makes it an effective antioxidant as well.

Our skin contains high concentrations of Vitamin C. Since we can’t produce it ourselves, this indicates that we’re regularly accumulating it through blood circulation. The deeper skin layer, the dermis, is vascular – meaning it’s rehydrated and receives nutrients through that circulation. The epidermis is not and therefore must rely on diffusion from the dermis.

Vitamin C concentrations are highest in the epidermis, likely because that’s where its antioxidant properties are most needed. Oxidative stress, caused by exposure to environmental factors like UV radiation, can deplete Vitamin C and other endogenous antioxidants. Interestingly, Vitamin C levels are have also been found to be lower in skin that is aged or photodamaged.

Does that mean we should be supplementing with Vitamin C if we’re outside often or seeing signs of photoaging?

Oral Vitamin C

While consuming it through diet is important, oral Vitamin C doesn’t necessarily have the same impact on skin compared to topical applications. One research paper concluded that “dietary supplementation is therefore only expected to be effective in elevating skin vitamin C in individuals who have below-saturation plasma levels prior to intervention.”

Essentially, oral Vitamin C may be helpful if you’re deficient but excess amounts are unnecessary. While synthetic ascorbate in supplements are just as bioavailable as whole food sources, you are missing on the additional micronutrients, dietary fiber, and phytochemicals.

Of course, oral Vitamin C has other benefits for the body but I’m going to keep this specific to the skin.

Topical Vitamin C
Applied topically, Vitamin C appears to benefit the skin directly and you’re not limited – like you are with oral supplementation – to cases where levels are low.

Vitamin C in skincare is primarily used as an antioxidant to neutralize reactive oxygen specifies (ROS) and protect the skin from UV damage or even damage to DNA. It’s also a tyrosinase inhibitor and can help with hyper pigmentation.

Ascorbic acid has some slight exfoliating benefits as well when it’s at pH 4 and below, though it can be irritating as a result. It may also help with collagen formation in the skin when applied topically – one study found that applying it daily for 4 months increased the thickness of the upper dermis.

Okay, so you want to use topical Vitamin C for maximum benefits for the skin. Does it matter what product or form of Vitamin C? Let’s discuss.

Effective Topical Formulations

Ascorbic Acid

Vitamin C in its active form is called ascorbic acid (or ascorbate). It’s similar to the Vitamin A family – to in that retinoic acid is the active form of Vitamin A and all retinoids must undergo conversion or they’re not helpful (see the full post here). You’ll often see it called L-Ascorbic Acid but this doesn’t need to concern you much. D-Ascorbic Acid and L-Ascorbic acid are isomers and found in equal parts in nature but only L-AA is active and used in skincare.

Ascorbic Acid is a tricky molecule to formulate with. It’s highly unstable so it needs to be carefully packaged and additional antioxidants are used to help stabilize it so it doesn’t oxidize too quickly. Because it’s a charged molecule and water soluble, it’s also difficult to get into the skin. At a lower pH, you have more protonated ascorbic acid which has a neutral charge. And it may have better antioxidant ability at a low pH too.

What to Look For:

• 15-20% Ascorbic Acid
• pH under 3.5 but 2-3 is even better
• additional antioxidants like ferulic acid and Vit E to stabilize the L-AA and enhance photoprotection
• ideally light and air tight packaging

Vitamin C Derivatives

You may be thinking… If Ascorbic Acid is so unstable and tricky to formulate, why not just use a derivative?

While it’s true that they’re more stable and much easier to formulate with, they also lack any real research behind them. There’s a few with some studies done that I will list below but because ascorbic acid is that much more proven, I would skip unless you can’t tolerate it in its active form.

The other issue is that in order to be effective, these derivatives must be able to be converted to L-AA. Many of these derivatives not only don’t have much in the way of topical research but haven’t been shown to increase levels of ascorbic acid in the skin.

So essentially, not all Vitamin C derivatives are created equal. Ascorby Palmitate was found to not only be ineffective, but an in vitro study found it could potentially intensify damage to skin cells after UV exposure. Source.

Recommended C Derivatives:

• Magnesium Ascorbyl Phosphate. A stable form of Vitamin C that has good antioxidant abilities and may also help with collagen formation and inhibiting pigment formation. Hydrating effect on skin. Research mainly done in lab conditions.
• Tetrahexydecyl Ascorbate and Ascorbyl Isopalmitate. Structural isomers that are often mixed up though ATIP appears to be a bit more researched. Better penetration and uptake into the cells vs L-AA but research is primarily from manufacturers and brands.
• Sodium Ascorbyl Phosphate. Not very effective as far as anti aging benefits go but its antibacterial properties make it a good choice for acne.

Like with ascorbic acid, I highly recommend looking for products that future other antioxidants as well. Vitamin C works synergistically with other antioxidants so you get better photoprotection in addition to their help in keeping L-AA stable. Water soluble antioxidants also act differently than fat soluble or enzymatic forms, protecting intracellular fluids instead of cell membranes. So using an array really provides superior protection.

THD/ATIP can also enhance penetration of ascorbic acid in addition to photoprotection.

Want specific recommendations? See the last section below.

Vitamin C Favorites

These are my recommendations for Vitamin C products based on formulation and extensive testing. Skincare should always be selected based on your skin concerns and goals so I’ve separated them into categories based on who I recommend each for.

For full reviews on each and their ingredients, watch my YouTube video on Vitamin C.

Dry or Mature Skin:

• Skin Actives 20% Vitamin C Serum
• NCN Pro Skincare Vitamin C+ Serum
• Ausceuticals Vitamin C 20% Serum
• Regimen Labs Vitamin X

All Skin Types (including Oily/Combo):

• Dermalure C+ Serum 15%
• Dermalure C+ Serum 20%

Hyper-Pigmentation:

• Dermalure Intensive Night Serum

Sensitive Skin (or use these as a secondary antioxidant with your ascorbic acid):

• Skin Actives Antioxidant serum (MAP)
• Kate Ryan Daytime Repair C (THD)
• MooGoo Skincare 25% in Squalane (ATIP)

Budget Options (most skin types):

• Geek & Gorgeous C Glow

Comment below and reshare if this was helpful! And please share your Vitamin C favorites as well, I’m always curious to hear what you’re using.

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