Glutathione
gamma-L-glutamyl-L-cysteinyl-glycine
TL;DR
Glutathione is the body's principal intracellular antioxidant, but oral glutathione is largely broken down into its constituent amino acids before absorption. Liposomal and sublingual forms raise blood markers modestly; NAC remains the better-evidenced way to raise glutathione.
Ideal For
- People who cannot tolerate NAC
- Adjunct interest in oxidative stress conditions
- Skin tone concerns, with modest expectations
Avoid If
- Expecting intravenous-grade effects from an oral capsule
- Considering IV glutathione for cosmetic use
- Asthma, where inhaled forms have triggered bronchospasm
Frequently Asked Questions
Overview
Glutathione is genuinely central to human biochemistry and genuinely difficult to supplement. In the gut, gamma-glutamyltransferase in the intestinal brush border cleaves it, so most of an oral dose arrives in circulation as free glutamate, cysteine and glycine rather than intact tripeptide. This is why the supplement industry has moved toward liposomal, sublingual and acetylated forms — and why the more useful strategy is often to supply the rate-limiting precursor instead. Cysteine availability, not glutathione intake, limits synthesis, which is the argument for N-acetylcysteine, a compound with a far larger clinical evidence base including its use as the antidote in paracetamol poisoning. That said, some trials of oral and liposomal glutathione have reported increases in body stores and in markers such as the reduced-to-oxidised ratio and natural killer cell activity over several months. The skin-lightening use, popular in parts of Asia, has some trial support through tyrosinase inhibition but the intravenous version carries documented safety concerns and is not something to pursue.
How It Works
- Substrate for glutathione peroxidase, reducing peroxides
- Conjugates toxins in phase II liver detoxification
- Regenerates oxidised vitamins C and E
- Synthesis is rate-limited by cysteine, not by glutathione intake
Quick Facts
- Intestinal enzymes cleave most oral glutathione before absorption
- Cysteine availability is the real rate limiter
- NAC has a much larger clinical evidence base
- IV glutathione for skin lightening carries real regulatory warnings
Benefits & Outcomes
Phase II Detox Support
Glutathione is genuinely central to phase II conjugation, but oral glutathione is a poor way to raise it. NAC supplies the rate-limiting precursor and has far better evidence.
Reduced Oxidative Stress
Oral glutathione is poorly absorbed; NAC or sulforaphane are more effective routes to raising it.
Glutathione Enhancement
Standard oral glutathione absorbs poorly; liposomal forms do better but the evidence base is thin.
Supporting Research19 studies
A randomized placebo-controlled pilot study of N-acetylcysteine in youth with autism spectrum disorder
Wink LK, Adams R, Wang Z +5 more
NAC up to 60 mg/kg/d for 12 weeks was well tolerated and raised plasma glutathione-related markers but produced no significant improvement in social impairment versus placebo.
Selenium and the Immune Response
Arthur JR, McKenzie RC, Beckett GJ
Selenium deficiency impairs natural killer cell activity, T-cell proliferation and antibody responses, and increases susceptibility to viral infection, partly through loss of glutathione peroxidase and thioredoxin reductase protection of immune cells. Supplementation improves immune measures mainly in people with low baseline selenium status; benefits in replete individuals are not established.
N-acetylcysteine in a Double-Blind Randomized Placebo-Controlled Trial: Toward Biomarker-Guided Treatment in Early Psychosis
Conus P, Seidman LJ, Fournier M +4 more
Six months of NAC 2.7 g/d increased brain glutathione levels measured by magnetic resonance spectroscopy but did not improve the primary positive symptom outcome.
N-acetylcysteine and oxidative stress biomarkers: a systematic review and meta-analysis of randomized trials
Sadowska AM, Manuel-Y-Keenoy B, De Backer WA
NAC consistently restored glutathione levels and lowered markers of lipid peroxidation and oxidative injury.
Early enteral nutrition with whey protein or casein in elderly patients with acute ischemic stroke: a double-blind randomized trial
de Aguilar-Nascimento JE, Prado Silveira BR, Dock-Nascimento DB
Hydrolyzed whey protein feeding was associated with changes in glutathione peroxidase and inflammatory markers versus casein, but the trial was small and several comparisons were not significant.
The role of methionine on metabolism, oxidative stress, and diseases
Martinez Y, Li X, Liu G
Methionine drives transmethylation, glutathione synthesis and polyamine production, but excess intake raises homocysteine and oxidative stress.
Selenium and antioxidant status in health and disease
Rayman, M.P.
Review of selenium biology: selenium is incorporated into around 25 selenoproteins including glutathione peroxidases and thioredoxin reductases. Status varies widely by soil geography, and both deficiency and excess carry risk, with a narrow optimal intake window and a U-shaped risk curve for several outcomes.
Effect of whey vs. soy protein supplementation on recovery kinetics following speed endurance training in competitive male soccer players: a randomized controlled trial
Kritikos S, Papanikolaou K, Draganidis D +5 more
When total protein intake was already adequate, neither whey nor soy protein altered reduced glutathione or redox status recovery compared with isoenergetic placebo.
Whey Protein Supplementation Improves Nutritional Status, Glutathione Levels, and Immune Function in Cancer Patients: A Randomized, Double-Blind Controlled Trial
Bumrungpert A, Pavadhgul P, Nunthanawanich P +2 more
Whey protein supplementation raised blood glutathione levels and improved nutritional and immune indices compared with control in cancer patients.
Alpha-lipoic acid supplementation and oxidative stress markers: a systematic review and meta-analysis
Akbari M, Ostadmohammadi V, Tabrizi R +3 more
Alpha-lipoic acid significantly reduced malondialdehyde and increased total antioxidant capacity and glutathione.
N-acetylcysteine, oxidative stress and protein misfolding: a systematic review of clinical evidence
Tenorio MCDS, Graciliano NG, Moura FA +2 more
NAC reliably raised glutathione and reduced markers of protein oxidation and carbonylation across clinical populations.
Glutathione as a skin-lightening agent and in melasma: a systematic review
Sarkar R, et al.
Topical versus oral glutathione both provide moderately efficacious skin-lightening outcomes... IV glutathione is contraindicated due to lack of efficacy and side effects.
Randomized controlled trial of oral glutathione supplementation on body stores of glutathione
Richie JP, Nichenametla S, Neidig W +4 more
Oral glutathione supplementation for six months resulted in increases in body stores of glutathione of 30-35% in blood and 260% in buccal cells at the higher dose.
Glutathione as an oral whitening agent: a randomized, double-blind, placebo-controlled study
Arjinpathana N, Asawanonda P
Melanin indices were consistently lower with oral glutathione than placebo over four weeks
Bioavailability of orally administered reduced glutathione: a randomised, double-blind, placebo-controlled trial
Allen J, Bradley RD
No significant changes were observed in biomarkers of oxidative stress or glutathione status following four weeks of oral glutathione supplementation.
Glutathione as a skin whitening agent: Facts, myths, evidence and controversies
Sonthalia S, Daulatabad D
Evidence for oral and intravenous glutathione as a depigmenting agent is limited and of low quality
Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function
Sinha R, Sinha I, Calcagnotto A +4 more
Oral administration of liposomal glutathione elevated body stores of glutathione and enhanced markers of immune function.
N-acetylcysteine and glutathione precursor supply in glutathione deficiency: mechanisms and clinical implications
Sekhar RV, Patel SG, Guthikonda AP +4 more
Supplementing elderly subjects with the glutathione precursors cysteine and glycine fully restored glutathione synthesis and concentrations and lowered oxidative stress.
Glutathione as a depigmenting agent: an overview of clinical evidence
Sonthalia S, Jha AK, Lallas A +2 more
Evidence for the skin-lightening efficacy of glutathione is limited to small studies with short follow-up, and the intravenous route carries significant safety concerns.
Safety Information
Potential Side Effects
Oral glutathione is well tolerated; occasional bloating, cramping and loose stools. Long-term high doses may lower zinc. Inhaled forms can trigger bronchospasm in asthma.
Contraindications
Intravenous glutathione for skin lightening has been associated with serious adverse events including Stevens-Johnson syndrome and renal impairment, and regulators have warned against it.
Drug Interactions
- Chemotherapy agents — theoretical reduction in oxidative efficacy; oncology input needed
- Paracetamol — glutathione is consumed in its metabolism
- Zinc — long-term high-dose use may reduce levels
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
250-1000 mg
Best Time to Take
Once daily, away from food
Best Form
Liposomal or sublingual glutathione; or NAC as a precursor
Bioavailability
Poor for standard oral glutathione owing to intestinal gamma-glutamyltransferase; liposomal and acetylated forms improve it substantially but not completely.
Forms Compared
Liposomal glutathione
Sublingual / S-acetyl glutathione
Standard reduced glutathione
NAC (precursor)
Food & Timing
Take on an empty stomach to limit digestive breakdown.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.