Glutathione
Also referenced as: GSH, L-glutathione, reduced glutathione
The body's principal intracellular antioxidant tripeptide, widely supplemented and modestly evidenced.
- Evidence grade
- CEarly Human Research
Early Human Research
- Regulatory status
- Not FDA Approved
Available as a dietary supplement, which is regulated as a food rather than a drug. Injectable glutathione for skin lightening is not approved, and regulators have warned about unapproved injectable products.
- Human data
- Yes
Registered clinical trials exist
- Last reviewed
- September 1, 2026
Overview
Glutathione is a tripeptide of glutamate, cysteine and glycine present in every human cell, where it is central to redox balance and detoxification.
Its biological importance is beyond dispute. Whether supplementing or injecting it meaningfully changes health outcomes is a much weaker claim.
Why It's Being Studied
- Oxidative stress and redox balance in ageing and chronic disease.
- Hepatic detoxification pathways.
- Skin pigmentation, where cosmetic claims are common and poorly evidenced.
Mechanism of Action
It is the cell's main antioxidant, neutralising reactive molecules and helping the liver process toxins.
Glutathione cycles between reduced (GSH) and oxidised (GSSG) states, serving as cofactor for glutathione peroxidases and S-transferases in phase II conjugation. Oral bioavailability is limited by intestinal hydrolysis; cysteine availability is typically the rate-limiting factor for endogenous synthesis.
Research Areas & Routes Studied
- Oxidative stress
- Liver function
- Skin pigmentation
- Neurological disease
- Oral
- Intravenous (clinical and cosmetic settings)
- Nebulised (research)
Evidence Summary
Human studies exist for oral and intravenous forms across several endpoints, but they are small and inconsistent, and cosmetic skin-lightening claims are not supported by robust evidence.
Human clinical evidence
- Trials of oral supplementation report modest increases in body stores with inconsistent clinical endpoints.
- Small studies of oral glutathione and skin pigmentation report limited effects with poor durability.
Clinical trials
- Registered trials in Parkinson's disease, liver disease and cystic fibrosis.
Observational evidence
- Low glutathione status is associated with numerous disease states; causality is unresolved.
Reported Adverse Events in Research
- Oral use is generally well tolerated.
- Injectable use carries infection and hypersensitivity risk, and regulators have reported serious adverse events with unapproved injectable skin-lightening products.
Limitations of Current Evidence
- Poor oral bioavailability complicates interpretation.
- Cosmetic claims outstrip the evidence considerably.
Why It Is Used
- Longevity
Healthy Ageing and Longevity
The category with the largest gap between ambition and evidence, and the one where the quality of the underlying research matters most.
Read the case study
Research References
- Randomised controlled trial
Oral supplementation with glutathione and body stores: randomised trial
- Regulatory document
Registered glutathione trials