BACKGROUND: Glutathione is an important intracellular anti-oxidant involved in different cellular and body functions. In recent years, glutathione-containing products have become extremely popular as evidenced by the proliferation of these products especially for 'skin whitening'. The investigators conducted this exploratory study in preparation for further investigations to validate the efficacy and safety of glutathione-containing products.
OBJECTIVES: 1) To describe the different glutathione products, their claims on efficacy and safety, as advertised on the Internet; 2) To report the best current evidence on the claims of efficacy and safety of glutathione supplements and glutathione-containing products for the skin.
METHOD: An online search for glutathione distributors was conducted from February to March 2008 to find out their claims on the efficacy and safety of glutathione-containing supplements or IV glutathione. For the search of the best current evidence on glutathione products, various electronic databases were searched up to September 2008 for any human clinical trials or reports of adverse events. Key informants were also interviewed.
RESULTS: From the Internet search, there were 20 brands oftopical glutathione products, 21 oral preparations, and 2 injectable glutathione products. There were also a variety of glutathione formulations available, mainly capsules containg glutathione plus other antioxidants. All products claimed a skin 'whitening' effect. There were no published human clinical trials, whether quasi-experimental or controlled trials (ex. RCTs) supporting the claims of skin whitening or skin rejuvenating effects of glutathione. There was one unpublished randomized controlled trial and one local clinical trial ongoing in the Philippines. No adverse events associated with glutathione products were reported in published literature. Anecdotal reports of adverse effects were gathered during key informant interviews.
CONCLUSIONS: The evidence on whitening and skin rejuvenation effects and safety is insufficient because these are based on testimonials and anecdotal reports, all of which are at high risk of bias. The magnitude of glutathione's skin whitening effect nor its side-effects have not yet been established.
RECOMMENDATIONS: Good quality, randomized, controlled trials are needed to validate claims of skin 'whitening' from the use of glutathione supplementation or glutathione skin products. Health professionals and consumers should document and report adverse events related to glutathione-containing products for the sake of public safety.