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Oxidized glutathione is studied for the first time as a topical skin-whitening antioxidant.
F Watanabe et al., “Skin-whitening and skin-condition-improving effects of topical oxidized glutathione: a double-blind and placebo-controlled clinical trial in healthy women,” Clinical, Cosmetic, and Investigational Dermatology, published online October 17, 2014.
Thanks to its melanin-inhibiting properties, reduced glutathione has become a popular oral option to whiten and brighten skin. However, researchers recently uncovered a similar topical application for glutathione’s oxidized form that’s showing promising results. A tripeptide of cysteine, glycine, and glutamate, glutathione is an important antioxidant in the body and occurs in both reduced and oxidized forms.
In a recent study, 30 Filipino women aged 30–50 years applied 0.5 g of oxidized glutathione lotion to one side of their face and a placebo lotion to the opposite side twice daily for 10 consecutive weeks. The study was randomized, matched-paired, and double-blinded. Skin whitening, moisture, firmness, and smoothening, as well as wrinkle reduction, were objectively measured every week by researchers. Researchers and subjects also subjectively rated their skin along similar criteria.
Over the course of 10 weeks, average melanin index values quantified by a Mexameter MX18, corresponding to skin whiteness, decreased nearly 30 points on sites that received oxidized glutathione lotion, while the placebo sites saw only a slight decrease. Glutathione sites also had an increase in moisture and smoothness over placebo sites, as well as a reduction in wrinkles. Skin firmness did not appear affected by glutathione.
Until now, reduced glutathione was used to brighten skin by oral administration, but was ill-suited for topical application because it is unstable in aqueous form. Fortunately, oxidized glutathione is stable in aqueous form and is able to be used in lotions or creams.
Studies have shown that reduced glutathione inhibits melanin production by inhibiting tyrosinase activity, activating the pheomelanin pathway, and scavenging reactive oxygen species generated following UV exposure. Although researchers speculated similar processes may be at work in this study of oxidized glutathione, they say there have not been enough studies on glutathione’s oxidized form to say for certain.
“To my knowledge this is the first study on skin whitening with GSSG (oxidized glutathione) and healthy subjects,” said Karen E. Todd, RD, senior director, global brand marketing, Kyowa Hakko USA Inc. “Other studies have been on reduced glutathione and/or in vitro.” Todd also reported this is the first study of reduced or oxidized glutathione by topical application.
Further studies will hopefully clarify the exact mechanism by which oxidized glutathione works to brighten skin on a topical level. The experimental lotion used in this study contained 2% oxidized glutathione, which was provided by Kyowa Hakko Bio Company, Ltd. (Tokyo, Japan).
Nutritional Outlook magazine
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