A (ridiculously) deep guide to getting great skin with Vitamin C

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What makes Vitamin C such a good skincare ingredient?

There is a simple reason your dermatologist keeps recommending Vitamin C: topically applied Vitamin C is one of the best proven ways to keep your skin healthy.

Vitamin C improves your skin in 3 key ways:

Sounds great, right? Let's delve deeper into how Vitamin C works for your skin.

Benefit 1 — Vitamin C is an effective antioxidant that protects your skin from premature aging by sun damage

As you may know, UV rays from the sun are the main cause of premature aging of skin.

When your skin is exposed to UV rays, free radicals are spawned. These free radicals can then cascade through your skin like ricocheting bullets — tearing up collagen and wreaking havoc on your skin cells.

The damages caused by free radicals speed up the aging process in human skin, which we see visibly as sunspots, wrinkles, and ruptured blood vessels (called actinic purpura — bleeding from fragile capillary blood vessels just beneath the skin surface).

Of course, there is nothing wrong with getting older! But why rush it?

As you know, wearing a good broad spectrum SPF is still the most important thing you can do for anti-aging. However, even good sunscreens only block about half of the free radicals spawned from UV exposure (Telang et al 2013).

Free radicals are vicious on your skin and skin cells, so you want as much protection against free radicals as possible. That's where antioxidants come into play.

Antioxidants can clean up roving free radicals in your body like water puts out fire. So, ramping up topical antioxidants like Vitamin C is a great way to keep your skin looking youthful and healthy.

You can read more in depth about free radicals and skin health in Appendix A at the end of this writeup.

Benefit 2 — Vitamin C is a collagen booster, and it will help keep your skin firmer and bouncier

Collagen is what keeps your skin from wrinkling and sagging. Therefore, you want to preserve the collagen you have and continue regenerating it regularly.

Collagen is an elongated fibrous protein. When seen under a microscope, collagen looks like braided steel cables and provides structure and support to your skin like scaffolding under a tent.

We steadily lose collagen in our skin over time — roughly 1% per year — which leads to wrinkles and sagging as we get older. In women, collagen loss can be dramatically sped up during menopause.

Without the supportive collagen fibers, your skin loses strength and flexibility. Skin then begins to sag and wrinkle.

As we mentioned in the previous section, Vitamin C, in its role as an antioxidant, can protect and preserve collagen from destruction caused by UV exposure and free radicals. In addition, Vitamin C can also help rebuild and regenerate collagen as well, thereby partially reversing the negative effects of collagen loss.

Vitamin C boosts collagen formation both by fueling production of the building blocks of collagen (procollagen peptides) and by helping enzymes weave these peptides into collagen fibers.

So, you can think of Vitamin C as a collagen booster. If you want to keep away wrinkles and sagging as long as possible, Vitamin C can help.

Benefit 3 — Vitamin C brightens and evens out your skin tone by reducing hyperpigmentation

Hyperpigmentation is a condition when patches of skin get darker than their surroundings, and it occurs when there is an overproduction of melanin — the dark pigments responsible for skin color.

Common causes of hyperpigmentation are sun exposure and inflammation (such as acne). Excessive UV radiation and inflammation can stimulate melanocytes to push melanin production into overdrive. Melanin is encapsulated in organelles called melanosomes which are transported to the skin surface to induce pigmentation (DeDormeal et al. 2019).

Melanin typically serves to protect against UV radiation so in principle, is good for you. However, the aesthetic side effects of hyperpigmentation, sunspots, and melasma are often unwanted.

Vitamin C tempers overproduction of melanin, and helps keep the unwanted aesthetic side effects of hyperpigmentation at bay. Vitamin C inhibits the enzymatic activities that make melanin in your skin, so you get a brightening effect.

Then Vitamin C goes a step further. Vitamin C is also an effective anti-inflammatory that can promote skin healing, thus further helping to prevent unwanted blemishes and scars from forming in the first place.

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Wait! How about blue light?

Blue light is within the spectrum of visible light, and you can get blue light from a light bulb or a phone screen. While you only get UV light outside (from the sun), you can be exposed to blue light both indoors and outdoors, during the day and at night.

If you stare at a screen all day, you may be tanning your face a little with the blue light emitted by the screen (especially if your skin is very fair).

And it's possible that blue light can increase free radicals in your skin. Although, in our view, it's very unlikely that the blue light from screens can inflict significant damage to your skin.

There hasn't been much research on whether antioxidants work specifically against the effects from blue light exposure. However, we believe that Vitamin C should work just fine because antioxidants work against free radicals in general.

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OK, I'm convinced. What should I look for in a Vitamin C product?

Look for these 3 things at minimum: (1) 10% or higher ascorbic acid, (2) addition of Vitamin E and other antioxidants, (3) acidic formulation of pH 3.5 or below.

The presence of other antioxidants can help stabilize ascorbic acid and also boost the skin benefits. Think of these additional antioxidants as the supporting cast to the star, ascorbic acid.

You've probably already heard a lot about Vitamin C serums being acidic. The reason is because ascorbic acid needs to be in a low pH (acidic) formulation for it to be able to penetrate the skin surface barrier.

To summarize simply, electrically neutral molecules are potentially able to get through the water-proof skin surface barrier. And at a low pH, ascorbic acid is in an electrically neutral form. This is why effective Vitamin C serums are all acidic.

We suggest a product with a pH of 3.5 or lower, which is around the same acidity as wine.

The need for acidity is why we recommend Vitamin C serums in a water-based formula, rather than a cream. It's much easier to achieve the needed level of pH in a water-based formula.

You can read more about how ascorbic acid can be formulated to penetrate the skin surface barrier in Appendix B at the end of this writeup.

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If I already consume Vitamin C in my diet, do I need to also apply it on my skin?

You should apply Vitamin C directly on your skin because ingesting Vitamin C isn't enough to maintain optimum skin health.

The basic reason is simple. When you ingest Vitamin C, it's taking a long, roundabout way to reach your skin — going from gut to bloodstream to skin tissue. And there is a limit on how much Vitamin C can get absorbed and transported at each step.

For example, your gut will only absorb enough Vitamin C for critical body functions — such as staving off scurvy. Your gut isn't going to soak in extra Vitamin C just to maintain supple skin.

As we get older, we start losing those capillaries (micro-sized blood vessels that lie just beneath the skin surface) that carry nutrients to every nook and cranny of our skin. Therefore, even less nutrients can reach your skin cells via bloodstream as we age — further diminishing your Vitamin C supply.

Finally, as Vitamin C in the skin fights off free radicals generated by UV rays (and other environmental aggressors, such as second-hand cigarette smoke), Vitamin C is depleted from the skin at a faster rate than in other organs.

Think of your skin as the pawns in a chess game: the first line of defense against environmental attacks, but also the first to experience wear and tear. This is why it's vital to keep replenishing your skin with nutrients to continue healing from the wear and tear.

If you apply Vitamin C on your skin, it goes directly to your skin cells. Think of it as skipping the middlemen. It's just a much more effective, direct way of getting your skin the nutrient it wants.

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Are there other types of Vitamin C, or should I look specifically for ascorbic acid?

Yes, we think it's best to stick to ascorbic acid.

Ascorbic acid is the naturally occurring form of Vitamin C. The Vitamin C we find in foods (such as berries, vegetables, etc.) is of the ascorbic acid variety. And most importantly, our body can readily utilize ascorbic acid, which is why it is referred to as the most "bioavailable" form of Vitamin C.

Other ingredients you might see pitched as Vitamin C — such as ascorbyl phosphate, ascorbyl-palmitate, Tetrahexyldecyl Ascorbate, etc. — are derivative forms of Vitamin C, and these cannot be used by our body directly. These derivatives must first be converted to ascorbic acid in order for our body to use them.

That's not to say that the Vitamin C derivatives don't work — just that there is a lack of extensive evidence compared to ascorbic acid. Maybe they work, but why take the chance when there is a sure thing?

In conclusion, ascorbic acid seems to be the safest bet to ensure that you're getting the Vitamin C benefits you're looking for. Studies have proven that ascorbic acid, when formulated properly, can penetrate through the skin surface barrier and increase Vitamin C concentrations inside epidermal skin cells. It's less clear whether Vitamin C derivative formulations can do the same.

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Do I need to look specifically for L-ascorbic acid? Or is just "ascorbic acid" acceptable?

You definitely want L-ascorbic acid, however there is no need to look specifically for the L form because it's understood that everyone uses it by default.

FDA regulation specifies that L-ascorbic acid is listed as "ascorbic acid" in ingredient lists. Technically, it's a violation for a brand to put "L-ascorbic acid" in the ingredient list.

But if you want to be absolutely sure, contact the brand and ask to clarify if they use the L form of ascorbic acid.

You can read more about the L-form of ascorbic acid in Appendix D.

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Is more Vitamin C better? Should I look for products with a very high concentration?

In our opinion, if you apply the product daily then somewhere between 10 to 20% concentration is plenty to keep your skin cells well supplied with Vitamin C.

Interestingly, your skin might actually absorb less when Vitamin C concentration gets very high. It could be counterproductive when Vitamin C concentration goes above 20%.

We're aware that there is an arms race of products touting high concentrations of Vitamin C as the selling point. However, calibrating an effective skincare formulation isn't as simple as just overloading on an ingredient. There are many other factors to account for in formulating an effective skincare product.

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How often and when should I apply?

We recommend applying Vitamin C twice daily. This is because the level of Vitamin C in your skin is constantly being depleted 24 hours a day, day and night.

However, if your routine allows for just one application a day, then we recommend using Vitamin C as part of your morning routine. That way you start the day with the highest Vitamin C level as you face the environmental aggressors (UV rays, pollution, etc.).

During the day, your Vitamin C level is steadily depleted as Vitamin C is used to mop up free radicals. And while you sleep, Vitamin C is further depleted to fuel the heal-and-rebuild cycle of your skin.

So, the key is that you regularly replenish Vitamin C in your skin to keep fueling that protect → heal → rebuild cycle.

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Should Vitamin C be used when people have rosacea or acne?

Vitamin C can very well be beneficial to those with rosacea and/or acne due to its anti-inflammatory, wound-healing, and scar-prevention benefits.

That being said, the formulation necessary for Vitamin C serums might not necessarily be optimal for sensitive skin because the low pH can be potentially irritating for those skin types.

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What are the drawbacks of Vitamin C?

As every rose has its thorn, so does Vitamin C.

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Final thoughts

To recap, Vitamin C is an extensively studied and proven ingredient that protects, heals, and rebuilds your skin. Vitamin C can also reduce hyperpigmentation and brighten your skin tone.

If you aspire to achieve or maintain healthy and glowing skin, Vitamin C is one of the cornerstone ingredients you should have in your skincare routine. Make sure the Vitamin C product you pick meets this minimum checklist:

The best product is the one you'd actually use, so find a product that you enjoy using and stick to it regularly. As your doctor would tell you, adherence and consistency are the key to achieving success and retaining good results for the long run.

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Why we wrote this

There is so much information about skin care on the internet, and it can be overwhelming to figure out what to believe.

We wanted to summarize the main, validated scientific findings on the what and the how of beneficial skincare ingredients in a deep, but fun and easy-to-understand manner. That way, you'll be informed about how skincare ingredients and products work. You'll also be empowered to filter information and have more productive conversations with your physician.

This writeup is not a sales pitch but is meant to provide you with helpful information that can be verified with widely available public information. So, there are no mentions of any proprietary research or specific product recommendations.

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Appendix A — Free radicals and skin health

When UV radiation hits the skin, the photon of radiation interacts with trans-urocanic acid and oxygen in skin to generate reactive oxygen species (ROS) such as singlet oxygen (¹O₂) and superoxide anion (O₂⁻•), which sets off a chain reaction resulting in the creation of other ROS (Hansen and Simon 1998, Herrling et al. 2007, Kaźmierczak-Barańska et al. 2020, Poljsak and Dahmane 2012).

ROS and their free radical cascades destroy proteins, lipids (leading to lipid peroxidation), and nucleic acids and signal cell death (apoptosis) in the skin. ROS act like ricocheting bullets — damaging collagen, the extracellular matrix of the dermis, and cellular DNA — leading to solar elastosis and skin cancer. ROS also induce collagenases (enzymes which break down collagen) and together lead to photoaged skin (Hansen and Simon 1998, Herrling et al. 2007).

ROS scavenging molecules, known as antioxidants, are prevalent in skin and the main ones are Vitamin C (for the watery cytosol) and Vitamin E (for the fatty lipid layers). Antioxidants like Vitamin C work by donating electrons to neutralize free radicals (Telang 2013, Pullar et al. 2017, Traikovich 1999; Lin et al. 2005, Kaźmierczak-Barańska et al. 2020).

As the most plentiful antioxidant in the skin, Vitamin C prevents lipid peroxidation and protects the keratinocyte from apoptosis — all signs of skin protection (Pullar et al. 2017; Telang 2013, Traikovich 1999). Vitamin C as an antioxidant also serves as an anticancer agent (Nusgens et al. 2001).

Vitamin C is equally effective against harmful effects from both UVB and UVA. UVA penetrates deeper into the skin and damages the dermis — contributing to collagen breakdown and melanoma formation — while UVB damages the epidermis, contributing to epidermal mutations, skin cancer, and sunburn (Lin et al. 2005; Telang 2013, Traikovich 1999). Both UVA and UVB lead to premature aging of skin — lines, wrinkles, spots, and sagging.

Glycosaminoglycan synthesis as part of extracellular matrix formation is increased by Vitamin C, and Vitamin C may also influence gene expression of antioxidant enzymes involved in DNA repair. Vitamin C has hence been shown to increase repair of oxidatively damaged bases (Pullar et al. 2017).

Appendix B — Ascorbic acid and skin barrier penetration

The visible skin surface is called the stratum corneum. This outermost skin barrier is about the same thickness as a sheet of printer paper.

The stratum corneum is 15–20 layers of flattened cells that contain keratin and are further embedded in a lipid matrix of ceramides, cholesterol, and fatty acids. This structure makes the stratum corneum much less permeable and is hence a protective barrier that wraps our bodies. Think of the stratum corneum like a thin wetsuit for your body.

Water-fearing (hydrophobic) molecules that are typically lipophilic (fat-loving) are nonpolar (have no ionic charge) and can diffuse through the stratum corneum, while water-loving (hydrophilic) molecules have an ionic charge, which makes them easily dissolve in water but also makes them impermeable through the stratum corneum.

However, even for hydrophilic molecules such as Vitamin C, when in solution, they can exist in unionized (nonpolar) and ionized (polar) forms. At the pH of its pKa, a molecule exists in 50% ionized and 50% unionized forms. Unionized, nonpolar forms — like lipophilic compounds — can pass through the stratum corneum.

The pH of the formulation should be 3.5 or lower. At this pH, Vitamin C is protonated and uncharged — this both stabilizes Vitamin C in solution and allows it to be in a form that transports well across the stratum corneum (Pinnell et al. 2001; Lin et al. 2005).

Vitamin C at neutral pH cannot pass the stratum corneum. Ascorbic acid is polar, and hence hydrophilic in water at neutral pH. The stratum corneum does not allow polar particles through. The trick is that if pH goes below the pKa of a compound, the Vitamin C in solution will lose its charge and be mostly in the nonpolar form. Hence, at a low pH below 3.5, Vitamin C is nonpolar and slips through the stratum corneum. Once through that barrier, it can now be taken up by the SVCT receptors in the epidermis.

With a serum, you are getting an L-ascorbic acid which is hydrophilic — versus a lipophilic cream that has some other lipophilic version of Vitamin C that even though it passes through the stratum corneum, hasn't necessarily been shown to work if not converted to ascorbic acid enzymatically. No formulations have been as extensively studied and proven to be effective as those with L-ascorbic acid in a water-based solution.

Appendix C — How Vitamin C gets taken up by your skin cells

In order for a skincare ingredient to truly deliver its full benefit, it needs two levels of absorption. First, it needs to be able to get past the water-proof outer barrier of the skin (penetrate through the stratum corneum) as discussed above in considerations of pH.

Second, after getting past the stratum corneum, the ingredient then needs to be absorbed into skin cells in order to be utilized as nutrients. Scientists call this process of absorption of a substance by cells an "uptake."

SVCT works at the second level where it helps "transport" Vitamin C inside skin cells so the cells can utilize Vitamin C as a nutrient — in other words, SVCT enables ascorbic acid uptake by skin cells. SVCT also enables absorption of Vitamin C from your stomach and intestines into the bloodstream, as well as transporting Vitamin C out of the bloodstream into appropriate body tissues.

There is a limited amount of Vitamin C that can enter into the bloodstream irrespective of how much one ingests, because it is limited by the amount of uptake by the Vitamin C transporters in the gut. Your body doesn't need much Vitamin C for essential functions (such as fending off scurvy) so you won't necessarily absorb as much Vitamin C as you ingest.

Studies have shown that absorption of Vitamin C decreases to less than 50% when taking amounts greater than 1000 mg. In generally healthy adults, megadoses of Vitamin C are not toxic because once the body's tissues become saturated, absorption decreases and any excess amount will be excreted in urine.

Likewise in the topical application context, it is not possible to go beyond saturation. Your Vitamin C transporters will not transport beyond saturation — the worst thing you can do is waste product. Your skin will not be harmed even if you applied Vitamin C too much or too often.

The dermis, the deeper layer of skin, can get Vitamin C from the micro blood vessels that penetrate throughout it. But the epidermis, the skin surface layer, does not have direct access to the bloodstream. So it's most effective to directly administer Vitamin C to the epidermis by applying it on the skin.

The dermis transporters can pull Vitamin C into the skin from the bloodstream, but the epidermis depends on diffusion from the dermis unless it receives it from topical application. Dietary Vitamin C alone in the bloodstream can lead to a deficiency of Vitamin C in the epidermis, particularly with aging. Further, UV exposure depletes Vitamin C from the epidermis. Several reports indicate Vitamin C levels are lower in aged and/or photoaged skin (Pullar et al. 2017).

Appendix D — More about ascorbic acid and its chiral forms

There are two isomers of Ascorbic Acid (L as in 'levo' and D as in 'dextro'). The thick triangles in molecular diagrams are the molecule sticking out at you and the hashed lines are the molecule going into the page. The configurations are different — differences that can be seen more clearly in 3D models.

The reason you want L-ascorbic acid goes back to the SVCT transporters. You need transporters to get the hydrophilic Vitamin C into the cells or else it will not work. Both of the primary Vitamin C transporters (SVCT1 and SVCT2) show much greater affinity for the L- rather than the D- form. So that's why you need the L- form — because SVCT transporters don't have good affinity for the D-form (Carr and Vissers 2013).

You sometimes get the "R" and "S" nomenclature for enantiomers of a chiral compound — R = right or clockwise, and S = sinister, which means left in Latin, or counterclockwise.