Glutathione
Evidence Fact Sheet
GSH · Reduced L-Glutathione · Liposomal · S-Acetyl
Glutathione (GSH) is the body's main intracellular antioxidant tripeptide, studied as oral reduced, liposomal, or S-acetyl supplements (250-1000 mg/day). Evidence includes a direct oral-GSH RCT raising body GSH stores and a small metabolic RCT; skin and liver directions remain mechanism-only. US GRAS; no EFSA-authorized claim.
Also known as: GSH · GSSG · L-Glutathione · Reduced glutathione · Liposomal glutathione · S-Acetyl glutathione · Setria · γ-L-glutamyl-L-cysteinyl-glycine
Overview
Glutathione (GSH · γ-L-glutamyl-L-cysteinyl-glycine) is the body's principal endogenous antioxidant tripeptide. Mechanistically it scavenges ROS/RNS, regenerates vitamins C and E and CoQ10 in the cellular redox cycle, serves as cofactor for glutathione peroxidase and substrate for Phase-II glutathione-S-transferase conjugation, and is studied for Nrf2/ARE pathway activation. In research contexts it is supplemented as reduced, liposomal, or S-acetyl GSH, typically at 250-1000 mg/day over 3-6 months; plain reduced GSH has low oral bioavailability, so liposomal and S-acetyl forms are the studied delivery routes. Regulatory status: a lawful dietary supplement ingredient with GRAS status in the US under DSHEA, an authorized constituent under ANVISA IN 28/2018 in Brazil, with no EFSA-authorized health claim in the EU. This page summarizes research findings in studied populations and is not medical or dosing guidance.
Mechanism of Action
Direct ROS/RNS free-radical scavenging in research models · Regeneration of other antioxidants (vitamin C, vitamin E, CoQ10) in the cellular redox cycle · Cofactor for glutathione peroxidase (GPx) and substrate for glutathione-S-transferase (GST) in Phase II conjugation pathways studied in mechanistic work · Nrf2/ARE pathway activation upregulating endogenous antioxidant gene expression (research-context) · Tyrosinase inhibition shifting melanin synthesis from eumelanin toward pheomelanin in mechanistic skin-pigmentation studies · NF-κB suppression in preclinical inflammation models
Body systems: Cellular Renewal · Liver & Detoxification · Immune System · Skin & Connective Tissue · Mitochondrial & Cellular Energy
Evidence-Based Benefits
Each benefit below is anchored to a specific PubMed-indexed study. Effect sizes, sample sizes, and p-values are reported as published; no values are inferred. Honest negatives and null results are kept alongside the positive findings, and disease-research populations are described as such — Glutathione is not characterized as a treatment for any disease.
Body Glutathione Stores (Antioxidant Capacity)
RCT supported- 30-35 %blood GSH rise · 1000 mg · P<0.05
- 260 %buccal-cell GSH · 1000 mg
In the keystone direct oral-glutathione trial, six months of supplementation raised body glutathione stores in a dose-dependent way: the high-dose group showed roughly 30-35% increases across blood compartments and a large rise in buccal cells, while the low-dose group showed smaller blood increases. Levels returned to baseline about one month after stopping, indicating a reversible, supplementation-dependent effect.
Reported effect: GSH levels increased 30-35 % in erythrocytes, plasma and lymphocytes and 260 % in buccal cells (P < 0.05) in the high-dose (1000 mg/day) group; 17 and 29 % in blood and erythrocytes in the low-dose (250 mg/day) group; levels returned to baseline after a 1-month washout.
“GSH levels increased 30-35 % in erythrocytes, plasma and lymphocytes and 260 % in buccal cells (P < 0.05). [low-dose group] GSH levels increased 17 and 29 % in blood and erythrocytes, respectively (P < 0.05). Levels returned to baseline after a 1-month washout period.”
Source: PMID 24791752 · Richie 2015 · Eur J Nutr
Insulin Sensitivity & Oxidative-Stress Markers (Metabolic)
Null / no benefit RCT supportedIn a small randomized trial of obese males with and without type 2 diabetes, three weeks of 1000 mg/day oral GSH significantly improved whole-body insulin sensitivity and numerically raised skeletal-muscle GSH. The honest negative: it did NOT alter markers of oxidative stress — mitochondrial H2O2 emission and urinary RNA/DNA oxidation products were unchanged — so the metabolic effect was not explained by reduced oxidative damage. Sample size is small (n=20).
Reported effect: Whole body insulin sensitivity increased significantly in the GSH group; skeletal muscle GSH numerically increased (~19%); oxidative-stress markers (mitochondrial H2O2 emission, urinary 8-oxoGuo and 8-oxodG) did not change.
“Whole body insulin sensitivity increased significantly in the GSH group. Skeletal muscle GSH was numerically increased (∼19%) in the GSH group; no change was seen in GSH to glutathione disulfide ratio. ... Oral GSH supplementation improves insulin sensitivity in obese subjects with and without T2DM, although it does not alter markers of oxidative stress.”
Source: PMID 33740389 · Søndergård 2021 · Appl Physiol Nutr Metab
Immune-Response Modulation (Liposomal GSH, T2DM Population)
RCT supported- 3 monthsliposomal GSH · T2DM
- ↑ IFN-γ, TNF-α, IL-2Th1 cytokines
In adults with type 2 diabetes, three months of oral liposomal glutathione shifted ex-vivo immune responses against Mycobacterium tuberculosis — raising Th1-associated cytokines (IFN-γ, TNF-α, IL-2), lowering IL-6 and IL-10, reducing oxidative stress across blood components, and lowering intracellular mycobacterial burden. This is a specific pathological population, not a healthy-population study, and the abstract reports directional findings without an extractable effect-size number.
Effect size: this study reports the direction of the finding but does not state a specific numeric effect size, so none is given here rather than estimated.
“L-GSH supplementation for 3 months in people with T2DM was able to reduce the levels of oxidative stress in all blood components ... increased the levels of Th1-associated cytokines, IFN-γ, TNF-α, and IL-2 and decreased levels of IL-6 and IL-10 ... significantly reduced the burden of intracellular mycobacteria.”
Source: PMID 34150674 · To 2021 · Front Cell Infect Microbiol
Aging Hallmarks (GlyNAC Precursor Combination — NOT Direct GSH)
RCT supported- 16 weeksGlyNAC vs alanine placebo
The strongest aging/mitochondrial signal attributed to glutathione comes from GlyNAC — a glycine + N-acetylcysteine PRECURSOR combination, NOT direct oral GSH. In this randomized placebo-controlled trial, 24 older adults received GlyNAC or isonitrogenous alanine placebo for 16 weeks; the abstract describes outcomes (glutathione, oxidative stress, function) as improved/corrected but reports them in qualitative language with no extractable effect-size number, and confirms the regimen was safe and well-tolerated. This evidence must not be presented as direct GSH supplementation.
Effect size: this study reports the direction of the finding but does not state a specific numeric effect size, so none is given here rather than estimated.
“Twenty-four OA and 12 young adults (YA) were studied. ... GlyNAC (N = 12) or isonitrogenous alanine placebo (N = 12) for 16-weeks ... GlyNAC supplementation in OA for 16-weeks was safe and well-tolerated.”
Source: PMID 35975308 · Kumar 2023 · J Gerontol A Biol Sci Med Sci
Dosage (research context · not a recommendation)
Research-context dosing: 250-1000 mg/day reduced/liposomal/S-acetyl GSH studied over 3-6 months. Richie 2015 (PMID 24791752) raised body GSH stores at 250-1000 mg/day × 6 months (returned to baseline ~1 month after stopping). Plain reduced GSH has low oral bioavailability (<5%, hydrolyzed by γ-glutamyltransferase), so liposomal or S-acetyl forms are the studied delivery routes. No established Upper Limit; 1000 mg/day × 6 months showed no serious adverse events. Educational reference only, not a dosing recommendation.
Regulatory Status · 4 Markets
- US · FDA
- Lawful dietary supplement ingredient under DSHEA (1994); L-glutathione holds GRAS status for food use. Structure/function claims (antioxidant, skin health, liver support) permitted with the mandatory DSHEA disclaimer and 30-day FDA notification. 'Whitening/lightening' phrasing carries drug-claim risk and should be expressed as 'supports even skin tone'. No FDA-authorized SSA health claim exists for glutathione.
- EU · EFSA
- EFSA has NOT authorized any glutathione health claim under Reg (EU) 432/2012 (Art. 13/14). GSH is a non-essential nutrient not on the Union authorized-claims list; member-state regulatory status varies. No authorized EU health claim available.
- CN · China
- China SAMR: L-glutathione is on the list of substances usable in health food but requires registration (efficacy via clinical trial); no standing authorized claim; general-food only via yeast-extract side-door with no quantitative GSH claim and no whitening/antioxidant claim.
- BR · ANVISA
- Glutationa IS an authorized constituent in IN 28/2018 Anexo I (glutathione from E. coli W fermentation), with intake limits in Anexos III/IV — a compliant supplement route already exists (sold in Brazil as a supplement). It carries no IN 28/2018 Anexo V alegação funcional (no authorized functional claim).
Safety
Generally well tolerated in trials up to 1000 mg/day for 6 months; occasional mild GI upset/bloating, rarely rash. No known absolute contraindication, but data are insufficient in pregnancy, lactation, and children — not for these groups. Intravenous GSH data must NOT be extrapolated to oral supplements. GlyNAC (glycine + N-acetylcysteine) trial data are a precursor combination and must NOT be presented as direct oral-GSH evidence. Bioavailability claims require formulation-specific data; "100% absorption" type absolute claims are not supportable.
Related
Goals: longevity-stack · skin-beauty
Lifestyles: senior-60-plus
References
PubMed-indexed citations anchoring the benefit findings above. Effect sizes are reported as published.
- PMID 24791752 · Richie 2015 · Eur J Nutr — Body Glutathione Stores (Antioxidant Capacity)
- PMID 33740389 · Søndergård 2021 · Appl Physiol Nutr Metab — Insulin Sensitivity & Oxidative-Stress Markers (Metabolic)
- PMID 34150674 · To 2021 · Front Cell Infect Microbiol — Immune-Response Modulation (Liposomal GSH, T2DM Population)
- PMID 35975308 · Kumar 2023 · J Gerontol A Biol Sci Med Sci — Aging Hallmarks (GlyNAC Precursor Combination — NOT Direct GSH)
Frequently Asked Questions
1. Did glutathione improve metabolic outcomes in trials?
In a small 3-week randomized trial of 20 obese males with and without type 2 diabetes (Søndergård 2021, PMID 33740389), 1000 mg/day oral GSH significantly improved whole-body insulin sensitivity. Importantly, it did NOT change markers of oxidative stress, so the metabolic effect was not explained by reduced oxidative damage. The sample is small and the finding needs replication.
2. Isn't there strong evidence glutathione slows aging?
The most-cited aging signal comes from GlyNAC — a glycine + N-acetylcysteine precursor combination, not direct oral glutathione. In a randomized trial of 24 older adults over 16 weeks (Kumar 2023, PMID 35975308), GlyNAC was reported safe and well-tolerated with improvements described qualitatively. Because GlyNAC is a precursor combination, this should not be read as evidence for taking glutathione itself.
3. What about glutathione for skin whitening?
On this evidence page the skin/pigmentation direction is supported by mechanism only (tyrosinase inhibition shifting melanin synthesis) — no direction-specific oral-glutathione RCT with an extractable effect size was identified in our verified set. Regulators treat 'whitening/lightening' phrasing as a drug claim; in the US it is framed as 'supports even skin tone,' and EFSA has authorized no glutathione health claim.
Last evidence review: 2026-06-13