Antioxidants' value in skincare products remains controversial
The buzzword of the moment is "antioxidants." People are drinking green tea by the cupfuls, and antioxidant-containing vitamin waters are flying off the shelves.
Mushroom creams high in topical antioxidants are vigorously applied in the morning, and vitamin C antioxidant night creams are the rage and being applied from face to foot. But is there any evidence to support the role of antioxidants in skincare?
Antioxidants are substances that contain a free electron that can be donated to another substance. For example, ascorbic acid, also known as vitamin C, is a common antioxidant added to skincare products to donate an electron to reactive oxygen species that degrade the lipids in the moisturizer. The amount of oxygen in the jar increases as the amount of cream is reduced. This means that the need for antioxidant protection of the formulation becomes more important as the product is used, accounting for increased spoilage of the last little bit of cream in the jar.
The antioxidant that is used to ensure skincare product stability, however, does not necessarily function as a topical antioxidant. It's also difficult to prevent a topical antioxidant from becoming oxidized when it is applied to the skin surface and becomes in contact with environmental oxygen. How much really functions to prevent oxidative damage to the dermis is unknown.
Measuring the effectiveness of topical and oral antioxidants is also difficult. Even though antioxidants are commonly orally consumed in the form of vitamins C and E, it is hard to know if the antioxidant ability of the body is improved by increased consumption. Questions have been raised as to whether the ingestion of high doses of vitamin C is physiologically beneficial or simply creating expensive urine.
Further, since vitamin C is consumed with sun exposure, it must be continually ingested to maintain vitamin C stores. It is unknown how much vitamin C should consumed to optimally maintain skin antioxidant stores.
The only currently available method of analyzing the antioxidant ability of the skin is the sunburn cell assay. This test requires the use of Fitzpatrick skin type I or II individuals with a predetermined minimal erythema dose (MED). Subjects are administered 2MEDs of solar-simulated UV radiation and then a 3 mm punch biopsy. The sunburn cells or the apoptotic cells are then counted.
Next, subjects apply the antioxidant cream or consume the antioxidant supplement for a specified period. Then the 2MED radiation is repeated, followed by a second sunburn cell count. The two counts are compared to determine if the antioxidant offered any protective effect against sunburn cell formation. This is a crude method of assessing antioxidant benefit, but few other vetted methods exist.
Should patients use topical antioxidants as part of a sun-protective regimen and consume antioxidant supplements? To be sure, antioxidants' value in oral and topical applications remains controversial.
Zoe Diana Draelos, M.D., is a Dermatology Times editorial adviser and consulting professor of dermatology, Duke University School of Medicine, Durham, N.C. Questions may be submitted via e-mail to firstname.lastname@example.org
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