Glutathione

Glutathione (also known as GSH, L-Glutathione, γ-Glu-Cys-Gly, Reduced glutathione) is a anti-aging research peptide. The body's master antioxidant and the most abundant intracellular thiol. An unusual gamma peptide bond makes it resistant to normal peptidases — and its depletion tracks almost every disease of ageing.

Glutathione is a tripeptide of glutamate, cysteine and glycine, present in millimolar concentrations inside virtually every cell and functioning as the primary intracellular redox buffer. Its distinguishing structural feature is the γ-carboxyl linkage between glutamate and cysteine, which protects it from cleavage by standard peptidases; only γ-glutamyl transpeptidase can break it. The reactive cysteine thiol neutralises reactive oxygen species, regenerates vitamins C and E, conjugates xenobiotics for phase II hepatic detoxification, and maintains protein sulfhydryl status. The GSH:GSSG ratio is one of the most widely used biomarkers of cellular oxidative stress. Depletion is documented in liver disease, neurodegeneration, HIV, diabetes and ageing generally. As an administered compound its central problem is bioavailability: oral glutathione is largely hydrolysed in the gut, which is why liposomal, sublingual, intravenous and inhaled routes are used, and why precursors such as N-acetylcysteine are often preferred for raising intracellular levels. Intravenous glutathione has become popular for skin lightening, an off-label use that prompted the Philippine FDA to issue a public warning after reports of serious adverse events including Stevens-Johnson syndrome, thyroid dysfunction and renal impairment.

1 Mechanism of action

Serves as the electron donor for glutathione peroxidases in reducing hydrogen peroxide and lipid hydroperoxides; oxidised to GSSG and recycled by glutathione reductase using NADPH. Conjugates electrophiles via glutathione S-transferases for phase II detoxification, regenerates ascorbate and tocopherol, and maintains protein thiol redox state. Inhibits tyrosinase and shifts melanogenesis from eumelanin toward pheomelanin — the basis of its skin-lightening use.

Primary targets: Glutathione peroxidases · Glutathione S-transferases · Glutathione reductase (recycling)

2 Reported effects

Effects below are those reported in the published literature cited on this page. They are not claims of clinical benefit and not medical advice.

2.1 Reported benefits

• Primary intracellular antioxidant and redox buffer
• Essential cofactor for phase II hepatic detoxification via glutathione S-transferases
• Regenerates vitamins C and E to their active forms
• Maintains protein thiol redox state and mitochondrial function
• The GSH:GSSG ratio is a validated biomarker of oxidative stress
• Depletion is documented across liver disease, neurodegeneration and ageing

2.2 Side effects

• Serious cutaneous reactions with high-dose IV use — Stevens-Johnson syndrome and toxic epidermal necrolysis reported
• Thyroid dysfunction reported with IV administration
• Renal impairment reported with high-dose IV use
• Abdominal cramping and bloating with oral dosing
• Injection site reactions and infusion reactions
• Paradoxical hypopigmentation or uneven pigmentation from cosmetic use

3 Chemical and physical properties

3.1 Amino acid sequence

4 Research dosages

Oral studies: 250–1000 mg/day (bioavailability limited). IV protocols in the literature vary from 600 mg to 2400 mg — the higher end is associated with reported serious adverse events.

5 Research studies (6)

1. Creatine plus β-Hydroxy-β-Methylbutyrate supplementation is associated with preserved glutathione redox-balance and redox-function associations in older adults: a secondary analysis of a randomized crossover trial.
   Biogerontology (2026) · RCT
   Oxidative stress contributes to age-related musculoskeletal decline, partly through disruption of glutathione-dependent redox homeostasis.
2. Redox regulation: mechanisms, biology and therapeutic targets in diseases.
   Signal transduction and targeted therapy (2025) · Review
   Redox signaling acts as a critical mediator in the dynamic interactions between organisms and their external environment, profoundly influencing both the onset and progression of various diseases.
3. Mechano-activated connexin hemichannels mediate intercellular glutathione transport and support lens redox homeostasis.
   Redox biology (2025) · Preclinical
   Redox homeostasis and transparency in the ocular lens are closely associated with the distribution of the antioxidant reduced glutathione (GSH).
4. Mitochondrial Glutathione in Cellular Redox Homeostasis and Disease Manifestation.
   International journal of molecular sciences (2024) · Review
   Mitochondria are critical for providing energy to maintain cell viability.
5. Lysosomal cyst(e)ine storage potentiates tolerance to oxidative stress in cancer cells.
   Molecular cell (2023) · Preclinical
   Cyst(e)ine is a key precursor for the synthesis of glutathione (GSH), which protects cancer cells from oxidative stress.
6. The role of glutathione in periplasmic redox homeostasis and oxidative protein folding in Escherichia coli.
   Redox biology (2023) · Preclinical
   The thiol redox balance in the periplasm of E.

6 Safety and risk profile

6.1 Regulatory status

Glutathione is currently classified as Not approved. It has no approved human indication in the United States; availability elsewhere does not imply demonstrated safety or efficacy.

Safety score: 72/100 — low concern. Derived from clinical data volume, known risks and regulatory status.

6.2 Contraindications

Conditions and populations in which use is contraindicated:

• Known hypersensitivity to glutathione or sulphur-containing compounds
• Asthma (sulphite-sensitive individuals may react to thiol compounds)
• Pregnancy or lactation (IV use)
• Active renal impairment (high-dose IV)

6.3 Drug interactions

6.4 Long-term risks

• Unknown consequences of chronically suppressing physiological oxidative signalling
• Renal and thyroid effects reported with sustained high-dose IV use
• Zinc depletion reported with prolonged high-dose supplementation
• Sterility and contamination risk with repeated compounded IV administration

6.5 Research best practices

• Store lyophilised at −20 °C, protected from air — the thiol oxidises readily to GSSG
• Reconstitute immediately before use; solutions degrade quickly on exposure to oxygen and light
• Where the goal is raising intracellular GSH, precursor strategies (NAC + glycine) are better characterised
• Verify reduced (GSH) versus oxidised (GSSG) content — assays that report total glutathione hide degradation

7 Frequently asked questions

Is oral glutathione absorbed?

Poorly. Most is hydrolysed to its constituent amino acids in the gut, and the evidence that oral dosing meaningfully raises intracellular glutathione is weak. Liposomal and sublingual formulations improve on this somewhat; N-acetylcysteine or glycine plus NAC supplies the rate-limiting precursors more efficiently.

Why is IV glutathione used for skin lightening?

Glutathione inhibits tyrosinase and shifts melanin synthesis from dark eumelanin toward lighter pheomelanin. This use is off-label and unapproved; the Philippine FDA has issued a public warning after reports of Stevens-Johnson syndrome, toxic epidermal necrolysis, thyroid dysfunction and renal failure associated with high-dose IV administration.

Why does glutathione resist digestion inside the body?

The glutamate-cysteine bond is a γ-peptide linkage rather than the standard α-linkage. Ordinary peptidases cannot cleave it — only γ-glutamyl transpeptidase can — which is why it survives as a stable intracellular pool.

8 References

1. Creatine plus β-Hydroxy-β-Methylbutyrate supplementation is associated with preserved glutathione redox-balance and redox-function associations in older adults: a secondary analysis of a randomized crossover trial. PubMed (2026). Ramos-Hernández R, et al.. View source
2. Redox regulation: mechanisms, biology and therapeutic targets in diseases. PubMed (2025). Li B, et al.. View source
3. Mechano-activated connexin hemichannels mediate intercellular glutathione transport and support lens redox homeostasis. PubMed (2025). Wang G, et al.. View source
4. Mitochondrial Glutathione in Cellular Redox Homeostasis and Disease Manifestation. PubMed (2024). Chen TH, et al.. View source

9 See also

• Peptide encyclopedia index
• Peptide reconstitution calculator
• Glossary of peptide research terms