Vitamin C or ascorbic acid is one of the most researched skincare ingredients and probably one of the most common.
Ascorbic acid is a key antioxidant and a cofactor in at least eight vital enzymatic reactions. This vital vitamin destroys free radicals and plays a major role in the formation of collagen everywhere in the body, including the skin. Problem is, humans can’t produce vitamin C because we lack the enzyme which converts glucose into ascorbic acid. Almost all mammals are luckier than us in that respect being able to create vitamin out of sugar, but we don’t have this excuse for having a sweet tooth. At least getting a sufficient intake of vitamin with food is not very difficult, especially at a young age.
Normally, high contents of ascorbic acid are present in the dermis and epidermis. Ascorbic acid in the skin can be damaged or destroyed by environmental pollution agents, such as ozone, by smoking and by ultraviolet radiation. Sadly, the level of vitamin C also decreases with age for reasons yet unknown.
In the epidermis vitamin C levels drop 31% when the skin is damaged by the sun and 39% in mature skin. In the dermis, the levels of vitamin C are 37% lower in photo-damaged skin and 30% lower in ageing skin. Lower contents of ascorbic acid lead to wrinkles, loss of elasticity and other signs of ageing. Same happens with vitamin E.
If low level of vitamin C in the skin correlates with unwanted skin changes, then increasing it should bring about positive development, shouldn’t it? Vitamin C has been successfully applied in skin care since 1980s. The promised skin benefits are well known: wrinkle reduction, thicker epidermis, reduced UV damage, skin lightening and improvement in acne because of its ability to decrease squalene oxidation in the sebum. Vitamin C is one of the key ingredients of skin care during menopause.
Does this sound a little too good to be true? Well, there is another side of the coin: it is very difficult to deliver vitamin C to the skin in a stable, effective and non-irritating form.
Furthermore, the effect of vitamin C topical application varies widely from person to person, some users report all kinds of benefits from their vitamin C products, while others can’t detect any difference at all. Why is that? It has been discovered that people with high dietary intake of vitamin C experience very little or no effect from skincare with vitamin C. Taking vitamin C supplements or simply maintaining a healthy diet with plenty of vegetables and fruit brings the level of vitamin C in the skin up to the point where it can’t increase any more because of saturation.
The first thing stopping vitamin C from penetrating into the skin is the keratinous layer or stratum corneum. When the skin surface is too rough, almost none of vitamin C gets through. Peeling, exfoliation and dermabrasion can help with that. The tricky bit is that for every form of vitamin C there is an optimal pH level ensuring its penetration into the skin. For example, ascorbic acid is stable at pH below 3.5 and won’t get absorbed by the skin if its pH is higher than 4.0, which makes for a pretty acidic environment. Moreover, ascorbic acid oxidises when dissolved in water, so water should not come first on the list of ingredients of a skincare product with ascorbic acid.
The best way to apply vitamin C in this form is a very low pH, but not too watery, gel-like serum with a relatively high contents of alpha-hydroxy acids. Such products can be quite harsh on the skin and are definitely not the best choice for sensitive skin or in the summer heat. Ascorbyl palmitate has the same limitations being irritating and it penetrates into the skin slower.
Other forms of vitamin C, such as sodium ascorbyl phosphate (SAP), magnesium ascorbyl phosphate (MAP) and ascorbyl 2-phosphate 6-palmitate (APPS) are more easily manageable. They are all stable at pH 7.0 and quite popular, can be used even in cleansing products, however if an emulsion or cream with one of these forms of vitamin C is slightly more acidic, the results will be less impressive and slower to manifest. Nonetheless, these are all quite effective.
A new fat-soluble form of vitamin C has hit the market recently, ascorbyl tetra-isopalmitate (VC-IP). It is stable at pH < 5.0, penetrates deep into the skin and acts primarily on the dermis level, decreasing UV damage. It isn’t the best choice for acne management or skin lightening, but works well enough in anti-ageing and after sun products.
3-o-ethyl-ascorbate (EAC) is the gold standard of vitamin C where aesthetic effect is concerned. It penetrates into the skin easily (as long as the keratinous layer is not too rough) and acts on all levels; it is stable at pH 4.0–5.5, dissolves in water effectively turning into ascorbic acid, and is effective even in low doses. Compared to ascorbic acid, it’s effect is much stronger: 2% EAC lightens the skin just as well as 15%–20% ascorbic acid.
How to find the best product with vitamin C?
1. Pay attention to packaging. All forms of Vitamin C are fragile and can be damaged by air and light. Look for opaque airless pump bottles, single-use capsules or ampoules. I’d avoid products in classic tubes and glass jars, they could easily turn out to be a waste of money.
2. Stay away from water. Most forms of vitamin C oxidise as soon as they’re in contact with water. The best choice of vitamin C skincare product would be a cream or emulsion, maybe a gel. Avoid the ones that put water first in the ingredients list.
3. Read the label! If you see “ascorbyl…” or “ascorbic…”, then a product contains vitamin C. I am sorry to be the bearer of bad news, but sometimes cosmetic manufacturers claim their product contains vitamin C for marketing purposes without any real grounds for it. I’m afraid, “organic sweet orange extract” or “natural lemon oil” aren’t the same as vitamin C.
4. If you maintain a healthy diet, chances are you won’t be impressed by the effect of vitamin C skincare. Vitamin C is transported to the skin by the bloodstream and if you eat a sufficient amount of fruit and veg and/or take vitamin supplements, plasma levels can be saturated, and your skin will no longer react to vitamin C.
5. If you love suntan and/or are a smoker, most likely your skin will benefit from vitamin C in skincare. UV and smoke toxins destroy vitamin C in the skin, and in this case even the healthiest diet will not compensate for vitamin C deficiency.