Adequate dietary nutrient intake is necessary for healthy skin. In particular, vitamin C is required for the critical conversion of the amino acid proline to hydroxyproline in making collagen, which is a key structural protein of skin. However, vitamin C may have additional functions beyond its role in collagen synthesis.
Oxidation
Throughout the natural course of living and through exposure to harmful environmental factors such as cigarette smoke, pollution and ultraviolet sunlight, bodies produce substances known as free radicals, or reactive oxygen molecules. These molecules are variants of oxygen that are very reactive in the body. While they have important functions, they are highly destructive in excessive amounts. If left unchecked, free radicals damage DNA, cell membranes and the protein collagen.
Cure for Free Radicals
Within the body’s arsenal of defenses against free radicals lay the antioxidants. You’ve heard of these. They include certain nutrients such as vitamins E and C and the minerals selenium and copper as well as other food compounds--carotenes and flavonoids, for instance. Antioxidants sacrifice themselves to stabilize or “scavenge” the free radicals.
Topical Vitamin C
Theoretically, vitamin C applied to the skin should provide an extra boost of protect to the skin by scavenging the free radicals to which it is exposed. The questions remain: Does additional vitamin C beyond a healthy intake incur any benefit? And if so, can it be absorbed into the skin and used by those cells? In a review by Dr. Patricia Farris from the Department of Dermatology at Tulane University, research supporting a role of vitamin C in both preventing and treating photodamaged skin is laid out. Farris points out that oral vitamin C consumption does little to increase skin concentrations of vitamin C because absorption of vitamin C is limited. However, three different double-blind studies showed that topical vitamin C applications consistently and significantly reduced lines and wrinkles in various skin sites, including forearms, cheeks and eye areas.
More Than Antioxidant
This boost to skin appearance seems to go beyond just fighting free radicals and preventing damage. Topical vitamin C has been shown to increase collagen synthesis at the level of DNA by stimulating greater expression of two collagen genes. Because collagen is a structural protein, it firms up skin tissue. Research seems to support the usefulness of this nutrient in cosmetics to fight sun damage and skin laxity.
Not All Vitamin C Beneficial
In keeping with its usefulness as an antioxidant, vitamin C is a very unstable molecule. Exposure to air, heat and even light oxidizes vitamin C, rendering it far less effective. Furthermore, the precise form, concentration and delivery vehicle of vitamin C remains controversial. One of the more promising compounds to date is called magnesium ascorbyl palmitate (MAP), which crosses into the skin cells where it is converted to L-ascorbic acid, the effective form of vitamin C. Still, details on the best form, vehicle, pH and concentration have yet to be worked out.
