MikroScore
Science-backed ingredient evidence
Weak Evidence Safety: Likely safe Study dose: 500 mg/day

Glutathion

Also known as: Glutathione, Reduced Glutathione, GSH, Liposomales Glutathion, S-Acetyl-Glutathion

Summary Weak Evidence

Glutathione is the body's most celebrated antioxidant. As a supplement, the evidence is far less impressive than its reputation.

EU Health Claims: No approved claims

In the EU, no health claims have been approved for glutathione relating to anti-aging, detoxification, or immune boosting.

AI Summary

Quick verdict

Glutathione is the body's most celebrated antioxidant. As a supplement, the evidence is far less impressive than its reputation.

What the evidence supports

Glutathione is biologically central to the antioxidant and detoxification system. As an oral supplement, evidence for clear clinical benefits is limited and highly dependent on formulation and context.

What is NOT supported

Clinical human trials are absent or very weak. Long-term safety in humans is largely unexplored.

EU/EFSA status

Not approved. In the EU, no health claims have been approved for glutathione relating to anti-aging, detoxifica…

Safety

Likely safe

This AI summary is generated from the structured data on this page.

What Is Glutathione?

Glutathione (GSH) is a tripeptide composed of glutamic acid, cysteine, and glycine. It is the most abundant intracellular antioxidant, with intracellular concentrations of 2–10 mmol/L in most tissues. The body synthesizes GSH endogenously; under normal conditions, external supply is not required.

Glutathione exists in two forms: reduced (GSH, the active form) and oxidized (GSSG). The GSH/GSSG ratio is a key marker of oxidative stress in tissue. GSH levels measurably decline with age: compared to young adults, tissue levels in older individuals are estimated to be 20–40% lower.

The Core Problem: Oral Bioavailability

Glutathione’s reputation far exceeds its practical supplementability via the oral route.

The problem: Oral glutathione (standard form) is broken down in the gastrointestinal tract by peptidases — primarily gamma-glutamyltranspeptidase (GGT) in the intestinal epithelium — into its constituent amino acids before systemic absorption can occur. The landmark Witschi study (1992, PMID 1618779) established this clearly: a single 3 g oral dose of glutathione did not raise plasma GSH levels — the tripeptide failed to arrive intact.

This means the standard outcome with oral GSH is that the body receives glutamate, cysteine, and glycine as building blocks — not the finished antioxidant machinery. Since cysteine is the rate-limiting amino acid for endogenous GSH synthesis, this may provide indirect benefit. But that is a fundamentally different claim from “glutathione is directly supplemented.”

Formulation Alternatives

Newer approaches attempt to improve bioavailability:

Liposomal Glutathione: GSH encapsulated in liposomes (lipid vesicles) partially bypasses gastrointestinal degradation. Richie et al. (2015, PMID 25602346) and Sinha et al. (2018, PMID 29062122) consistently show elevated blood GSH levels at 500 mg/day over 4–6 weeks (increases of ~30–52% in erythrocytes and whole blood). Clinical endpoints — disease prevention, physical performance, aging biomarkers — were not investigated in either trial.

S-Acetyl Glutathione (SAG): Acetylation protects the thiol group from oxidation and improves membrane permeability. Promising in vitro; human studies are sparse.

Intravenous Glutathione (IV-GSH): Bypasses the oral bioavailability problem entirely. Used medically in specific conditions — symptom relief in Parkinson’s disease (small trials), skin lightening in some Asian markets. Not accessible as an over-the-counter supplement.

GSH Precursors as a Strategy

Rather than supplementing glutathione directly, one can support endogenous GSH synthesis through precursors:

N-Acetylcysteine (NAC): The most extensively studied GSH booster. NAC supplies the rate-limiting amino acid cysteine and is medically established (acetaminophen overdose, acute bronchitis). NAC reliably raises glutathione levels across diverse study populations.

Glycine: Also a glutathione precursor; a glycine + NAC combination demonstrated significant GSH increases and metabolic improvements in a small RCT in older adults.

Sulfur-containing foods: Cruciferous vegetables (broccoli, Brussels sprouts) contain glutathione precursors and raise GSH levels in animal models; human data are less robust.

What Do the Studies Actually Show?

Positive and reasonably supported

  • Liposomal GSH consistently raises blood levels above baseline (Richie 2015, Sinha 2018).
  • NAC as a GSH precursor is well-supported for GSH-deficiency states and established medical indications.
  • IV glutathione has shown clinically measurable effects in small studies (Parkinson’s symptoms, neurological recovery).

Weakly supported or unclear

  • Whether elevated blood GSH from oral supplementation improves clinical endpoints has not been demonstrated in controlled trials.
  • No RCTs exist on the long-term effects of oral GSH on aging biomarkers, immune function, or disease incidence in healthy adults.
  • “Detox” claims for glutathione have no specific clinical evidence base.

Not supported

  • Oral GSH supplementation as a reliable method to alter cellular redox status in healthy individuals.
  • Anti-aging effects from GSH supplements in humans.
  • Immune boosting by oral GSH in healthy people.

Dosing

  • Standard dose (in studies): 500 mg/day oral or liposomal GSH
  • More effective alternative: 600 mg/day NAC (for GSH support in documented deficiency)
  • Timing: Fasted or morning intake is commonly recommended; combining with Vitamin C theoretically extends half-life by recycling GSSG back to GSH

Safety

Glutathione is considered likely safe at typical supplement doses. No serious adverse effects were reported in short-term studies lasting up to 6 months. Long-term safety with continuous oral intake has not been adequately studied.

Note: Glutathione inhibits tyrosinase and is marketed for skin lightening in some Asian markets. This application is not medically approved and is ethically contested; corresponding marketing claims would not be permissible under EU regulations.

EFSA and Regulatory Status

In the EU, there are no approved health claims for glutathione — neither for antioxidant protection, detoxification, nor immune function. The EFSA health claims evaluation system has not positively assessed any such claims for glutathione. Marketing assertions about “detox,” “anti-aging,” or “immune boosting” for glutathione supplements lack regulatory approval and are not permissible as health claims in the EU.

Glutathione is not classified as a Novel Food and may be sold as a dietary supplement, provided no unauthorized claims are made.

Honest Limitations

  • Standard oral GSH is pharmacologically problematic: it is cleaved before absorption.
  • Liposomal forms show improved blood levels, but no clinical endpoint studies exist.
  • Most studies on oral GSH are small (n < 60), short (< 6 months), and measure surrogate markers (blood levels), not clinically relevant endpoints.
  • Individual variation in GSH baseline and actual need is large and rarely accounted for in trials.
  • In vitro and animal studies — many of them impressive — do not translate directly to the efficacy of oral supplements in humans.

Bottom Line

Glutathione carries a strong biological reputation that has not yet been matched by its performance as an oral supplement. Its biological centrality is beyond dispute. But oral bioavailability remains the unresolved core problem. Those looking to support endogenous GSH synthesis are likely better served by NAC (600–1200 mg/day) — better studied, cheaper, and directly effective as a cysteine donor. Liposomal glutathione is a meaningful improvement over the standard form, but clinical evidence for real health outcomes in healthy adults is still outstanding.

Key Studies

Randomized controlled trial of oral glutathione supplementation on body stores of glutathione

Richie et al. (2015)

Small RCT (n=54): 500 mg/day oral glutathione over 6 months raised whole-blood GSH by ~30–35% and erythrocyte GSH by ~52%. No clinical endpoints were measured.

PubMed PMID 24791752

The systemic availability of oral glutathione

Witschi A et al. (1992)

Classic pharmacokinetic study: a single 3 g oral dose of glutathione did not detectably raise plasma GSH levels. Conclusion: standard GSH is cleaved in the gut before reaching systemic circulation.

PubMed PMID 1362956

Glutathione metabolism and its implications for health

Wu et al. (2004)

Review: glutathione is central to redox homeostasis, detoxification, and immune function. However, its biological centrality does not automatically imply a benefit from oral GSH supplementation.

PubMed PMID 14988435

Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function

Sinha R et al. (2018)

RCT (n=60): liposomal GSH (500 mg/day, 4 weeks) raised whole-blood GSH by ~40% and improved some immune parameters. Better than the standard form, but long-term clinical data are lacking.

PubMed PMID 28853742
Editorial notice: For most ingredients described here, no health claims are approved in the EU (Regulation (EC) 1924/2006). Evidence levels are editorial assessments of research quality — not health promises. This content is not a substitute for medical advice and does not constitute a recommendation to treat, alleviate, or prevent any disease.