Glutathione

Glutathione is an endogenous tripeptide (L-glutamate, L-cysteine, and glycine) synthesized inside virtually every cell in two ATP-dependent steps catalyzed by glutamate-cysteine ligase and glutathione synthetase. Its reactive thiol (-SH) group on the cysteine residue makes it the body's principal intracellular antioxidant: it neutralizes reactive oxygen species directly, serves as the electron donor for glutathione peroxidases in detoxifying peroxides, and conjugates xenobiotics via glutathione S-transferases in phase II detoxification. The reduced (GSH) and oxidized (GSSG) forms cycle continuously, and the GSH/GSSG ratio is a widely used index of cellular redox state. A central caveat for supplementation is that orally ingested glutathione is substantially hydrolyzed by intestinal and hepatic gamma-glutamyltransferase, so much of an oral dose is broken into constituent amino acids rather than absorbed intact.

Glutathione is naturally produced by the body and is not a treatment for any disease. Supplement evidence is mixed and its oral bioavailability is debated. A well-controlled trial by Richie et al. (Eur J Nutr 2015) reported that daily oral glutathione over 6 months raised body stores of glutathione in blood and buccal cells in a dose-dependent manner, though effects reversed after washout. In contrast, an earlier randomized, double-blind, placebo-controlled trial by Allen and Bradley (J Altern Complement Med 2011) found that 500 mg twice daily for 4 weeks produced no significant change in oxidative-stress biomarkers or glutathione status in healthy adults. This inconsistency — driven by differences in dose, duration, formulation, and endpoints — is why claims for oral glutathione should be treated cautiously rather than as established benefit.

Educational overview only — no dosing instructions in the public hub.

Oral glutathione is generally well tolerated at studied doses, with mild effects such as bloating or loose stools occasionally reported. Injectable and intravenous use carries meaningfully higher risk — including injection-site reactions, infection from non-sterile preparation, and rare hypersensitivity — and should only occur under clinical supervision; regulators including the US FDA and the Philippine FDA have warned against unapproved IV glutathione marketed for skin whitening after reports of serious adverse events. The long-term effects of high-dose supplementation are not well characterized. It should not be treated as a therapy for any disease.

For supplements, prefer standardized reduced-form (GSH) material with third-party testing confirming identity and purity, since glutathione readily oxidizes and label content is not guaranteed. Setria-type reduced glutathione is the specific ingredient used in several of the cited trials, so results do not necessarily generalize to other or unverified forms. Injectable/IV glutathione is a different regulatory and safety category from oral supplements and is frequently sold in unapproved, unregulated forms.

Sold as a dietary supplement in many jurisdictions; regulatory status and permitted health claims vary by country. It is not approved as a drug for antioxidant, anti-aging, or skin-whitening indications. Injectable and intravenous glutathione is regulated differently from oral supplements and, in most markets, is not approved for cosmetic or wellness use — several agencies have issued safety advisories against such products.