Sodium Ascorbyl Phosphate Explained (24 Studies): EVERYTHING You Need to Know!

by | Last updated Apr 18, 2020 | 60 comments

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Sodium Ascorbyl Phosphate (SAP), a.k.a that derivative of Vitamin C no one pays attention to. If there actually existed an effective “natural acne treatment” this would be it.

Unlike its older brother Ascorbic Acid, SAP isn’t an unstable brat that oxidizes quickly. Little research has been done on this lovely ingredient, but what’s out there is promising.

Let’s break down the science behind this lovely lone warrior and explain why you should be using it!

What is Sodium Ascorbyl Phosphate (SAP)?

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Mad Hippie Vitamin C Serum (10% SAP)

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It’s an OG acne-killing machine — that’s what. “Okay, that’s nice but can we talk science?” Sure.

Sodium Ascorbyl Phosphate (SAP) is a naturally occurring water-soluble derivative of Vitamin C. You know, that stuff you try overdosing on a little too late when you feel a plague’s about to hit.

It’s the most stable form of Vitamin C, meaning it won’t oxidize and go bad in a couple months, making it a preferable choice for cosmetic formulations. It’s more stable and bioavailable than Magnesium Ascorbyl Phosphate (MAP), Ascorbyl Palmitate, and Ascorbic Acid (among other Vitamin C derivatives). (12)

Unlike it’s powerful but bratty older brother Ascorbic Acid, it doesn’t like acidic environments and requires a pH of around 6-7. (3) It’s an antioxidant that reduces oxidative stress by neutralizing free radicals, effectively slowing down the aging process and formation of fine lines and wrinkles. (4)

When it’s well formulated, SAP has the ability to penetrate the epidermis (outer layer of skin where the stratum corneum and acid mantle lie) without causing irritation. (5)

What are the benefits of Sodium Ascorbyl Phosphate (SAP)?

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Instanatural Vitamin C Serum (20% SAP)

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  • Anti-aging.

We all know UVA and UVB radiation from sun exposure causes degenerative effects that speed along the aging process.

Sunscreen anyone?

Luckily SAP is a badass oxygen species scavenger that protects against UV damage, and enhances the photoprotective properties of sunscreen. (678)

Confused? Don’t worry, I gotchu. English translation = it prevents sunburn and makes sunscreens stronger, both of which are anti-aging necessities. 😉

Speaking of photoprotection, we all know how important that is when treating hyperpigmentation issues. If you didn’t know that, read my guide about treating hyperpigmetation to find out why. Much like a tyrosinase inhibitor, SAP has skin-lightening properties by inhibiting melanin production (melanin being the skin pigment responsible for all your hyperpigmention woes).

However, the research on the skin lightening benefits of SAP is scarce and needs to be examined more throughly. Paula’s Choice said it best:

“This form of vitamin C is potentially effective for brightening an uneven skin tone, although there isn’t much research supporting its use for this purpose over other forms of vitamin C.”

  • Badass natural acne-killer.

This is what appeals to me most about SAP. I’ve used this sexy lady in the past, and its anti-acne benefits are undeniable!

“Yeah, but who cares what you say. Where’s the the research punk?”

Yes yes, indeed. Luckily we have a couple studies that have measured the acne-fighting benefits of SAP. Let’s summarize them.

In a vitro study, a group of researches were able to show that a measly 1% concentration of SAP (yes, 1%) has strong antimicrobial effects against acne for 8 hours! (9) Mind you, there are products out there on the market with concentrations of 10% and above (for example, Mad Hippie’s Vitamin C Serum).

The same researchers also found that 5% SAP lotion used for 12 weeks produced excellent results in 76.9% of patients, which is considerably higher than other prescribed acne treatments. (10Best of all, it treats acne with no side effects. (11)

Not only that, for decades scientists have known that lipid peroxidation (i.e. the oxidation of sebum) plays a MAJOR role in the development of acne. In fact, there is evidence that “lipid peroxidation is the driving force behind the progression of comedogenesis and inflammation in acne.” (12)

Well guess what prevents sebum oxidation? SAP! Indeed, research has shown that it reduces sebum oxidation by up to 40%! (10)

UPDATE 8/9/2017: rereading this blog post I felt that I really needed to better hammer this point home. So here’s some additional info….

The oxidized byproducts of human sebum are hugely problematic for skin. They are, after all, what leads to acne and skin aging. For example, squalene peroxide “leads to comedogenesis (i.e. clogged pores), contributes to the development of inflammatory acne, and possibly wrinkling.” (22)

And this can occur for all kinds of reasons: ozone, sun exposure (particularly long UVA rays), cigarette smoke, the natural yeast like malassezia that live on our skin, environmental pollution etc. are shown powerful oxidizing agents of our skin oils. (2223, 24)

So the fact that SAP can prevent this by up to 40% is astonishing! Not only for the prevention of acne, but also as a very useful tool against aging and the damaging effects that pollution causes on our skin.

Now back to our originally scheduled programming…..

Moreover, other clinical trials have shown SAP has better efficacy (i.e. is MORE effective) than 5% benzoyl peroxide, 1% clindamycin phosphate, 0.1% adapalene (a.k.a differin). (101113, 14, 15)

Like I mentioned earlier, we still need more research to really see the extent of this bad boy’s badassery, but from what’s out there already it’s looking very promising.

How does Sodium Ascorbyl Phosphate (SAP) Work?

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Foxbrim Vitamin C Lotion (5% SAP)

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Since there is such limited research on SAP the evidence on how it works isn’t conclusive yet. The assumption is that it gets converted into Ascorbic Acid in the skin. Ascorbic acid is the holy grail powerful version of Vitamin C that unfortunately degrades quickly making it a pain in the ass to formulate in cosmetics. The bratty older brother, remember?

Related reading: Best Vitamin C Serums (Ascorbic Acid): Top 5 Picks for Glowing Skin

The hypothesis that SAP is converted into Ascorbic Acid came from a study done on mice. (16) Yeah yeah, I know what you’re thinking. “That was a study on rats though. Shit don’t apply to us man.”

Well guess what sucker?

There was another study comparing the bioavailability of 2% SAP vs. 2% ascorbyl glucoside in humans, and it just so happened that the skin treated with SAP had a markedly higher epidermal Ascorbic Acid content. (1718)

So while not conclusive, it seems pretty obvious genius. Whether SAP is more effective than Ascorbic Acid itself…. well, that’s another question entirely. I personally think yes, simply because my skin cannot tolerate ascorbic acid. I find it irritates me quite a bit if I try to use it more than once a  week.

The formulators of Mad Hippie’s Vitamin C Serum had a few interesting things to say on the whole sodium ascorbyl phosphate vs ascorbic acid topic. Here are the relevant bits from an email exchange with them:

“Ascorbic acid is not very easily absorbed through the skin’s lipid barrier so a high concentration of L-ascorbic acid is needed (usually 15-20%) to make an effective product. At this concentration, while it slowly absorbs, L-ascorbic acid can cause irritation and acne outbreaks for those with sensitive or acne prone skin. So while L-ascorbic acid has been around for a long time and it works for some people, we feel that there are better forms of Vitamin C now available.

The form of Vitamin C that we choose to use is called sodium ascorbyl phosphate (SAP). It is a form of Vitamin C that has a salt molecule attached to it, allowing it to easily penetrate the skin’s lipid barrier. Because this form of Vitamin C is easily absorbed and utilized by the skin, it is not associated with the irritation often experienced with L-ascorbic acid.

Furthermore, a lower concentration is needed for the same results, which also leads to less irritation. We use about 10% sodium ascorbyl phosphate which is equivalent to a much higher concentration of L-ascorbic acid because it is much more bioavailable. It is also phenomenally more stable, allowing longer shelf life, even once it has been opened.”

The company’s also won several skincare awards from a couple big name magazines, so there’s that too. I can’t vouch for how pertinent that information is because I’m personally unfamiliar with the magazines. But I do think their vitamin C serum is solid.

  • The takeaway.

Sodium Ascorbyl Phosphate (SAP) is a stable powerful antioxidant that provides photoprotection, increases the effectiveness of sunscreen,  lightens skin tone, fades discoloration, and fights acne.

Side Effects.

Yeah, how about none? Rarely can you say that about an active ingredient, but like I mentioned earlier — clinical studies have shown SAP is an effective acne treatment comparable to benzoyl peroxide, adapalene (Retinoid), and antibiotics without the side effects.

In fact, the irritation level is on par with the vehicle in most trials, meaning there is no irritation. (192021)

How to Use Sodium Ascorbyl Phosphate.

Because SAP is pH dependent it’s important to use it after chemical exfoliates or low pH serums. To get an idea of what that would look in a routine with all things being considered, here’s a cheat sheet.

Note: depending on what products you’re using, some of these steps won’t apply.

  1. Oil cleansing method, or oil cleanser.
  2. Gentle pH-balanced cleanser (5.5 or below)
  3. Low pH serums or toner. Wait 20-30 minutes.
  4. BHA. Wait 20-30 minutes.
  5. AHA (glycolic, lactic, mandelic). Wait 20-30 minutes.
  6. *Vitamin C (SAP)*
  7. Retinoids (Tretinoin [Retin-A], Retinol)
  8. Spot treatments or other actives (e.g. Benzoyl Peroxide, Azelaic Acid).
  9. Moisturizers.
  10. Occlusives (Vaseline, Aquaphor)

Alrighty, well that does it for our talk on SAP. Hope you’ve enjoyed it!



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