Glutathione

Glutathione (Reduced) — γ-L-Glutamyl-L-Cysteinyl-Glycine

Evidence & Status

  • Preliminary / Experimental
  • Preliminary

At a Glance

The body's most abundant endogenous antioxidant tripeptide, central to cellular defense against oxidative stress. Human evidence for therapeutic administration is indication-specific — a small open-label Parkinson's disease study and a historical chemotherapy-neuroprotection trial — rather than support for the broader range of uses sometimes claimed.

Plain English

Researchers study Glutathione because it's the cell's primary defense against oxidative stress. The clearest direct human evidence found in this review comes from two specific, small, older studies: an open-label trial in early Parkinson's disease (9 people, no placebo group) and a controlled trial showing it reduced nerve damage from a specific chemotherapy drug in gastric cancer patients. Broader claims — for fatty liver disease or fertility — did not have a verifiable source in this review and have been removed rather than repeated without support. IV glutathione is also used in some integrative and cosmetic clinics; that reflects real-world practice, not proven clinical efficacy.

Overview

Glutathione is the most abundant endogenous antioxidant tripeptide (γ-Glu-Cys-Gly, reduced form/GSH), present in virtually all mammalian cells and synthesized intracellularly from glutamate, cysteine, and glycine. It is central to cellular defense against oxidative stress and to detoxification and protein disulfide-bond chemistry. The oxidized dimer (GSSG) is a distinct entity requiring its own evidence base. Human intervention evidence identified in this review is indication-specific: a small (n=9), 30-day open-label study of IV glutathione in early Parkinson's disease reported symptom changes without a placebo control (Hauser et al., 1996); and a historical randomized controlled trial found IV/IM glutathione reduced cisplatin-associated neurotoxicity in a specific chemotherapy regimen for advanced gastric cancer (Cascinu et al., 1995). A review of the Parkinson's disease literature notes the evidence base remains limited and uncertain (Mischley et al., 2010). No adequately sourced human evidence for NAFLD or male-infertility claims was identified in this review, and those claims have been removed. IV glutathione is also reported in integrative and cosmetic-practice settings for purposes such as skin lightening; this reflects real-world/anecdotal use, not evidence of clinical efficacy or an endorsed protocol. Oral bioavailability is limited by gastrointestinal hydrolysis.

Research Summary

Glutathione's endogenous redox biology is extremely well established, but therapeutic-administration evidence is indication- and formulation-specific. A small open-label study (n=9) of IV glutathione in early Parkinson's disease reported symptom changes over 30 days without a placebo comparator — suggestive, not definitive. A historical randomized trial found IV/IM glutathione reduced cisplatin-induced neurotoxicity in a specific chemotherapy protocol for advanced gastric cancer — evidence specific to that regimen and population, not general chemoprotection. A subsequent review characterizes the Parkinson's disease evidence base as still limited. No citation supporting NAFLD or male-infertility efficacy claims was identified despite a targeted search, and those claims have been removed rather than carried forward unsupported. Oral bioavailability remains limited by intestinal hydrolysis.

Research Areas

  • Oxidative stress
  • Liver detoxification
  • Neuroprotection
  • Immune function
  • Skin health

Safety & Risks

Serious Risks

  • Potential immune modulation in autoimmune conditions (mechanism unclear); skin lightening at high IV doses raises safety questions about long-term melanin suppression

Reported Side Effects

  • Abdominal cramping (oral high-dose)
  • Zinc depletion with chronic high-dose use
  • Skin lightening (high-dose IV, dose-dependent)
  • Mild injection site discomfort
United States
OTC supplement; compounded injectable (IV/IM) used off-label in integrative and functional medicine clinics
United Kingdom
Available as OTC supplement; IV preparations available via compounding pharmacies
Australia
TGA-listed supplement; IV formulations available via compounding
Canada
Natural health product (OTC); compounded IV available via specialty pharmacies

Citations & Sources