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

What Was Tested

This randomized controlled trial paper looks at Glutathione.

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.

Who Took Part

The study group was 124 subjects.

PubMed tags the participants as women only.

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.

How the Study Was Run

In design terms this was a randomized, double-blind, placebo-controlled and parallel-group study.

Because people in this Glutathione study were split into groups at random, differences between the groups are less likely to reflect who happened to join each one.

As a double-blind Glutathione study, the assignments were hidden from both participants and investigators until the end.

A placebo (an inactive look-alike) gave the Glutathione group a baseline to be compared against.

The Glutathione group and the comparison group ran side by side rather than switching.

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.

What Was Measured

PubMed files the paper under topics including Cystine, Glutathione and Skin Pigmentation.

The authors tagged it with the keywords L-Cystine, L-Glutathione, eumelanin, oral supplementation and pheomelanin.

What This Means in Plain Language

The paper is a randomized, double-blind and placebo-controlled study of Glutathione in 124 subjects.

The abstract goes on to report its results in about 4 sentences; this page does not restate them, so read the paper for the findings and their limits.

The publication is from 2022 (Journal of cosmetic dermatology), a journal based in England.

More context: the Glutathione compound page, all human trials.