L-Glutathione

L-glutathione is the reduced form of glutathione, a naturally occurring tripeptide made from glutamate, cysteine, and glycine. It is central to cellular redox biology, serving as an intracellular antioxidant and cofactor for detoxification and peroxide-reducing enzymes. Human supplementation evidence is mixed and depends on formulation, dose, population, and duration. A 6-month randomized trial found oral glutathione increased glutathione stores in blood and selected cell compartments, while a shorter 4-week randomized trial found no significant change in oxidative stress biomarkers or erythrocyte glutathione status. Dermatology studies report modest skin-marker effects, but cosmetic skin-lightening claims should be handled conservatively.

Redox Biology

Glutathione is a major endogenous antioxidant and participates in peroxide reduction and detoxification pathways ^[1].

Supplementation Trials

One 6-month randomized trial found oral glutathione increased body glutathione stores, while a separate 4-week trial found no significant improvement in oxidative stress biomarkers ^[2][3].

Dermatology Evidence Boundary

Cosmetic skin-lightening evidence is limited and should not be presented as a reliable or recommended use ^[4].

Formulation and Duration Limits

Human supplementation studies are limited in size and duration; long-term safety for high-dose or nonstandard formulations is not established ^[2][3].

Skin-Lightening Risk

FDA warns that skin-lightening products may be illegal, unapproved, or contain harmful substances. Injectable or compounded glutathione for cosmetic use should not be promoted ^[5].