Antioxidants form the body's defense system against free radicals - unstable molecules that cause irreversible damage to tissues and have been implicated in skin aging and skin cancer.
Free radicals are produced by normal cell metabolism - oxidation - as well as exposure to ultraviolet (UV) radiation from the sun and environmental toxins like air pollution and smoking. Highly reactive molecules, free radicals are scavengers that search the body for unpaired electrons they can bind to. Antioxidants intercept and chemically interact with the free radicals to prevent them from destroying important cell constituents, including protein and DNA.
Many topical anti-aging products now include antioxidants in an attempt to limit the action of free radicals and reduce their detrimental effects. A number of vitamins, minerals, and enzymes function as antioxidants. While there is a large body of research on the role of antioxidants in preventing cancer and degenerative diseases, good placebo-controlled studies of their effect on the skin are relatively scarce.
Here is a brief summary of some of the most popular antioxidants and how they are thought to work in skin care:
Vitamin A
Vitamin A is necessary for good skin health, but overdosing orally can lead to dry, flaky skin with an orange-y cast and some temporary hair loss. Topical Vitamin A, in the form of retinoic acid (Retin-A or Renova) or the less potent retinol, has been used for years to treat acne and improve the skin's appearance. A number of studies show that retinoic acid is capable of increasing dermal collagen, decreasing inflammation, and normalizing abnormal or damaged skin cells. Regular use of retinoids can help improve fine lines and wrinkles as well as the texture of skin, and can correct mottled hyperpigmentation. In addition, retinoids can decrease the number of actinic keratoses - pre-cancerous skin lesions. Vitamin C
Vitamin C is the most abundant antioxidant in human skin. It has numerous functions, including suppressing free radicals and serving as a co-factor in the production of collagen. Vitamin C must be supplied from outside, as the human body is not capable of synthesizing it. It has been found that oral consumption does not substantially increase skin concentrations. However, topically applied vitamin C provides some protection from ultraviolet A and B radiation, especially when combined with vitamin E in a topical preparation. Topical vitamin C also stimulates collagen production, lightens hyperpigmentation, and helps acne and acne scarring. A number of clinical studies have demonstrated that topical vitamin C improves fine wrinkles and sagging, as well as sallowness and skin texture. Vitamin C is unstable when exposed to light, oxygen, and heat, so it is crucial to select a preparation that has demonstrated efficacy. A cosmetic dermatologist can help you find the right one.
Vitamin E
Eight naturally occurring molecules are grouped under the term vitamin E. Like vitamin C, E is supplied to the body by oral intake or topical application, and not synthesized directly. Most of the data on topical Vitamin E concerns its ability to protect the skin against the effects of the sun. Pre-application of vitamin E reduces redness and swelling associated with overexposure to the sun. This photo-protection is enhanced by the addition of topical vitamin C. Topical vitamin E is widely marketed to reduce the appearance of scars, but research in this area is inconclusive. The anti-aging properties of vitamin E are also unsubstantiated.
Green Tea
In-vitro laboratory tests show that the polyphenol compounds in green tea have antioxidant, anti-inflammatory, and anti-carcinogenic properties. These findings, along with some animal research, have led the cosmetics industry to promote green tea as an anti-aging product. Studies on human skin show that green tea protects against damage from UV light. However, a study published in 2005 found no significant improvement in signs of photoaging after green tea was administered orally and topically simultaneously. Green tea needs more study in order to recommend it as an anti-aging compound.
Alpha Lipoic Acid
This compound, produced in the body, is both water- and fat-soluble, making it readily absorbed into the skin. Laboratory studies have found alpha lipoic acid to be a potent antioxidant. In addition, it helps protect vitamins C and E within cells, which may account for its presumed ability to promote collagen synthesis. Clinical research shows that topical application of alpha lipoic acid improves fine wrinkling and scars. However, more data is needed to confirm these findings and to more clearly delineate alpha lipoic acid's usefulness in the anti-aging armamentarium.
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