Study summary · research use only
The effects of the oral supplementation of L-Cystine associated with reduced L-Glutathione-GSH on human skin pigmentation: a randomized, double-blinded, benchmark- and placebo-controlled clinical trial
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This 12-week randomized, double-blind, parallel-group, benchmark- and placebo-controlled human clinical trial evaluated oral supplementation with L-Cystine and L-Glutathione on skin pigmentation in 124 Asian female subjects. Participants were randomized into four equal groups receiving 500 mg L-Cystine plus 250 mg L-Glutathione, 250 mg reduced L-Glutathione alone, 500 mg L-Cystine alone, or placebo daily. Skin color was measured by spectrophotometry at baseline and after 6 and 12 weeks, and facial dark spots were assessed from digital photographs. The authors report skin lightening after 12 weeks of oral supplementation with L-Cystine and L-Glutathione, along with a reduction in the size of facial dark spots after 6 and 12 weeks, describing these changes as greater than with placebo, L-Cystine alone, or L-Glutathione alone.
Abstract
Glutathione has become a potential skin-lightening ingredient after the discovery of its anti-melanogenic properties. Various mechanisms of action have been considered to explain this property, one of them being the skewing of the melanin synthesis pathway toward the production of lighter pheomelanin instead of darker eumelanin, consequently producing a lightening effect. To evaluate the skin lightening and anti-dark spot effects of oral supplementation with L-Cystine associated with L-Glutathione as compared to placebo and benchmark. Effects of this L-Cystine-L-Glutathione oral combination were investigated in a 12-week randomized, double-blind, parallel-group, benchmark- and placebo-controlled trial involving 124 Asian female subjects. Women were randomly allocated into 4 equal groups (500 mg L-Cystine and 250 mg L-Glutathione, 250 mg reduced L-Glutathione, 500 mg L-Cystine, or a placebo, daily). Skin color was measured at baseline, after 6 and 12 weeks by spectrophotometry. Size and color of facial dark spots were determined from digital photographs. A significant skin lightening was observed after 12 weeks of oral supplementation with L-Cystine associated with L-Glutathione. This combination also induced a significant reduction in the size of facial dark spots after 6 and 12 weeks. It is noteworthy that the observed effects were not only significantly better than those obtained with placebo, but also with L-Cystine alone or L-Glutathione alone. The daily oral administration of 500 mg L-Cystine and 250 mg L-Glutathione during 12 weeks was a safe treatment to effectively lighten the skin and reduce the size of facial dark spots of Asian women.
pepmg summarizes the peer-reviewed literature and links to every source — it sells nothing, ships nothing, and gives no medical, dosing, or human-use guidance. Don't just trust this summary: follow the citation to its source and read it yourself. Research use only.