L-Glutathione
A three-amino-acid molecule that is the body's main internal antioxidant, taken orally for skin tone and brightness.
Small trials show trends rather than clean results, and oral bioavailability remains genuinely contested.
On the label: L-Glutathione. Also known as Glutathione, GSH, Reduced glutathione.
What it does for you
Included for tone and brightness. This is the ingredient in our formula with the least settled evidence, and we would rather say so than imply otherwise.
Why we use it
It has a plausible mechanism and small controlled trials behind it. We are not building a claim on it, and we do not think you should choose this product for it.
Mechanism
Glutathione is thought to shift melanin production toward lighter pigment types. The unresolved question is whether swallowed glutathione survives digestion well enough to raise levels inside cells at all.
Use level
Trials use 250 to 500 mg/day over 4 to 12 weeks.
Commonly confused with
Oral glutathione is not the same as intravenous glutathione, which is a separate practice with its own safety questions and is not something we endorse.
What the studies say
Melanin index and ultraviolet spots tended to be lower than placebo at all sites for both forms. At some sites, reduced glutathione significantly reduced wrinkles versus placebo, and a tendency toward increased skin elasticity was observed. No serious adverse effects. The wrinkle and elasticity results are secondary to pigmentation endpoints and are described as tendencies at several sites rather than uniform effects.
- Human in vivo (oral)
- n = Healthy female subjects randomized equally into three groups; total not stated in the abstract
- 12 weeks
Randomized, double-blind, placebo-controlled, parallel three-arm; reduced glutathione 250 mg/day, oxidized glutathione 250 mg/day, or placebo
Glutathione and its antiaging and antimelanogenic effects Weschawalit S, Thongthip S, Phutrakool P, Asawanonda P. Clinical, Cosmetic and Investigational Dermatology, 2017. DOI 10.2147/CCID.S128339
Authors reported no conflicts of interest. Total sample size is not stated in the abstract. Note that this trial, like the rest of the oral glutathione literature, was designed around pigmentation rather than the antioxidant support role this ingredient carries in the formula.
Oral glutathione at 250 mg once daily, 250 mg twice daily and 500 mg once daily showed significant reduction in melanin index versus placebo. Risk of bias assessment found almost equal numbers of studies at low and high risk of bias, and the authors describe the outcomes as moderately efficacious but unsustainable. Intravenous glutathione is contraindicated for lack of efficacy and side effects.
- Systematic review
- n = Five randomized controlled trials and one open-arm clinical study on oral glutathione
Systematic search of PubMed, Embase and the Cochrane library over 10 years, with level of evidence, strength of recommendation and risk of bias assessment
Glutathione as a skin-lightening agent and in melasma: a systematic review Sarkar R, Yadav V, Yadav T, P J, Mandal I. International Journal of Dermatology, 2025. DOI 10.1111/ijd.17535
Independent systematic review, included as the honest ceiling on what the oral glutathione evidence currently supports. Its endpoints are pigmentation and melasma, not antioxidant status, so it bounds the claim rather than confirming it.