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Glutathione (reduced L-glutathione, GSH)
The body's main intracellular antioxidant; supplemental forms are best studied for skin-lightening, with debated oral bioavailability for systemic effects.
What the evidence says
Glutathione doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from high-quality meta-analyses and randomised trials published 1983–2026 with a typical study size of 46 participants.
Based on 101 studies · 5 meta-analyses · 81 RCTs · 170 total participants
Confidence
High confidenceBy outcome
12 more outcomes with fewer studies not shown.
Only small RCTs and systematic reviews exist, with the most consistent effect being modest, often temporary skin-lightening; oral bioavailability is debated and no meta-analyses confirm systemic antioxidant benefit.
74 randomised trials
90% were about Glutathione in an audit of 50 of them
Every randomised or controlled trial of Glutathione indexed in PubMed, not a hand-picked subset. Meta-analyses and systematic reviews are deliberately excluded from this count: most of them cover many compounds at once, so counting them would inflate it.
PubMed · as of Sep 2026
45 trials ongoing or recruiting · 153 completed on ClinicalTrials.gov
29 of the completed trials have posted results
Registered trials show research momentum for Glutathione, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Oct 2026
Glutathione (GSH) is a tripeptide (glutamate-cysteine-glycine) and the body's principal intracellular antioxidant, central to detoxification and redox balance in the liver and elsewhere. As a supplement it's marketed for antioxidant support, skin brightening, and detox.
The catch is oral bioavailability: glutathione is broken down in the gut, so raising tissue levels by swallowing it is debated — the most consistent clinical effect is modest skin-lightening, and some trials in specific conditions (e.g. cystic fibrosis growth) are mixed.
Notably, supplying its precursors (cysteine via NAC, plus glycine — 'GlyNAC') often raises glutathione more reliably than glutathione itself.
Directly neutralizes reactive oxygen species and regenerates other antioxidants (vitamins C and E).
A cofactor for glutathione-S-transferases that conjugate and clear toxins and drug metabolites, especially in the liver.
Inhibits tyrosinase and shifts melanin toward lighter pheomelanin, the basis of its skin-lightening effect.
Discuss with your oncologist before using antioxidants.
Not well studied at supplemental doses — avoid without medical advice.
Antioxidants may theoretically interact with pro-oxidant chemotherapy — coordinate with your oncologist.
Tip: Take with a little food; reduce dose
Tip: Expected; reverses after stopping
Glutathione has an evidence score of 4.8/10 — emerging evidence based on 100 indexed studies. The body's main intracellular antioxidant; supplemental forms are best studied for skin-lightening, with debated oral bioavailability for systemic effects. Representative study: PMID 39444151.
The commonly studied dose of Glutathione is 250-1000mg/day oral reduced L-glutathione (skin-lightening trials often used ~500mg); liposomal/sublingual forms aim to improve absorption. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Glutathione is between meals. It can be taken on an empty stomach. Often taken on an empty stomach; liposomal/sublingual forms are used to limit gut breakdown.
Glutathione is generally well-tolerated and considered safe for most healthy adults at recommended doses. Reported side effects include mild GI upset, transient skin lightening (intended effect). How often they occur is not established for all of them. Use caution if any of these apply to you: Known glutathione/sulfur supplement hypersensitivity.
CoQ10
Likely helpsA lipid-soluble antioxidant central to mitochondrial energy production, with the strongest trial support for fertility/IVF outcomes and heart failure.
Alpha Lipoic Acid
Likely helpsUniversal antioxidant that works in both water and fat, supporting blood sugar control, nerve health, and cellular energy.
Berberine
Likely helpsActivates AMPK to regulate blood sugar, improve insulin sensitivity, and support lipid metabolism. Its only head-to-head trial with metformin cited here was a 36-person pilot, which does not show it can replace metformin.
Lactoferrin
Too few graded studiesA multifunctional iron-binding glycoprotein from milk with broad antimicrobial, anti-inflammatory, and immune-modulating properties.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 101 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.