L-Ascorbic Acid is - simply - the scientific name for Vitamin C in its purest from. And that's where the simplicity ends...

All of the other vitamin C ingredients that you'll find on labels - such as magnesium ascorbyl phosphate, ascorbyl glucosamine, and tetra-isopalmitoyl ascorbic acid - are derivatives of ascorbic acid, and each come with their own set of unique pros and cons that I'll be discussing in a future post (so keep on the look out).

There's a lot of confusion and misinformation out there about L-ascorbic acid specifically, and it's about time somebody clears this up.

In this post I'll be taking you through the what-you-need-to-know details - from the good and the bad to the facts and the fiction.

The Rap Sheet.

L-Ascorbic Acid (AA) is a, highly unstable, water-soluble antioxidant (available commercially as a dry, white powder) that needs to be at high concentrations and at a low pH in order for it to enter your skin and do good. (See "What it does for your skin" for specifics.)

TIP: Look for formulas with high concentrations (10%+) and a low pH levels (<3.5) for maximum effectiveness.

Typical concentrations range from 5% to 25%, but there is no definitive answer as to what is optimal. Some say 20% is the best for absorption, while others maintain that concentrations over 18% cannot be absorbed adequately. Another statistic points to a threshold of at least 10% to boost collagen synthesis.

Concentration. Regardless, at any concentration, from the moment it makes contact with the outside environment (through high storage temperatures, light, high pH values, and the presence of dissolved oxygen) it begins to destabilize and lose its effectiveness at a rate of 6% to 16% (when stored for four weeks at 45 degrees Celsius for four weeks, according to one study). What's more, even better-stabilized AA derivatives only last at intended concentrations for about three weeks

pH. Also important to its effectiveness, in terms of stability and permeability, is the formula's pH level: the lower the pH level, the more stable, permeable and effective it is. At higher pH levels, ascorbic acid degrades much more quickly, rendering itself irreversibly into a biologically inactive form. Or worse yet - might actually promote harmful free radical formation.

TIP: One way to tell if your Vitamin C has lost its effectiveness is to check its color. Oxidation reveals itself through a yellowish-brown tint.

Irritation. The downside to all this is that the more effective formulations (with the higher concentration, and the lower the pH) tend to be quite irritating - especially so for men, smokers, individuals with sensitive skin, rosacea, and those in poor general health. (source)

From personal experience, I can attest to this.  The first time I applied a high-concentration serum I nearly wanted to claw my face off -- every inch of skin treated felt itchy and aflame for a good fifteen minutes, although I must say, after the discomfort resided, my skin did look quite nice.

TIP: Another nice-to-know detail is that Vitamin C does not play nice with mineral-rich skin care products or copper peptides. When they get together, bad things happen (such as the visible graying of skin).

The Bright Side.

Because of everything above, many people correctly believe that ascorbic acid cannot be stabilized in aqueous formulations. However, tests reveal that if a formula is prepared and packaged correctly than ascorbic acid actually out-performs nearly all of its better stabilized derivatives.

Tip: Look for topical base creams that contain no water - they will be less irritating since any discomfort is primarily caused by hydrogen ions generated by acid disassociating in water.

In one study, results revealed that topical application (in both lipid and aqueous formulas) of ascorbic acid on human skin actually outperformed the derivatives magnesium ascorbyl phosphate (MAP) and ascorbyl tetra-isopalmitate (ATIP) in both antioxidant potential transepidermal water loss values. A similar study (source) revealed that AA was better absorbed by the skin than MAP in gel, gel-cream and cream formulations.

In yet another study comparing the effectiveness of microparticle AA compositions in anhydrous (without water) solutions, research revealed that when applied topically to the skin, MAP and sodium ascorbyl phosphate (SAP) did not increase levels of AA in the skin; had negligible free radical scavenging ability in comparison to AA; and (for SAP) required ten times the concentration of AA to induce equivalent neocollagenesis in cultured fibroblasts.

Tip: How a formula is packaged is important to maintaining its efficacy.  Look for tinted bottles that block out light, or go for individualized application packets - both help keep the ascorbic acid from oxidizing too quickly.

What's important about these findings, says Dr. Geoffrey Heber (a lead investigator in one of these studies in an interview with Cosmetic Surgery Times) is that "AA can be stabilized and absorbed percutaneously..." He goes on to say,

"... published studies show these derivatives suffer from disadvantages compared to ascorbic acid. Ascorbyl palmitate is no more stable than ascorbic acid in aqueous solution. Ascorbyl phosphates and glucoside are more polar and would be expected to have lower percutaneous absorption, that of magnesium phosphate having been reported to be less than two percent absorption from a three percent cream 48 hours after application to dermatomed cadaveric human skin. Ascorbyl phosphates contain only approximately 50 percent ascorbate by weight, and ascorbyl tetraisopalmitate contains only 15 percent ascorbate by weight."

Conclusion.

* L-ascorbic acid is not the hopeless and hapless cause that many say it is, nor is it any cure-all.
* A good vitamin C serum (in my opinion) would always include L-ascorbic acid in its formula, but with a derivative as well.
* For maximum effectiveness, formulas should be at high concentrations (10%+) and with low pH levels (<3.5).
* It would be free of water, heavy minerals and copper peptides...
* ... and packaged in small, fresh portions.
* Any noticeable coloring should be suspect.

Related posts:

Part 1: What is it? Vitamin C: An Investigation & Discussion

Part 2: What is it? Vitamin C: What it does for your skin

Part 4: What is it? Vitamin C derivatives

Five Best Vitamin C Serums