Glutathione
Glutathione is a three-amino-acid peptide that every cell makes for itself and uses as its main defense against oxidative damage. "Master antioxidant" is fair as biochemistry. As a supplement, glutathione is largely digested before it reaches the blood, and the precursor [NAC](/supplements/nac/) remains the better-studied way to raise it.
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What It Does
Cells assemble glutathione from glutamate, cysteine, and glycine in two enzyme steps, and cysteine supply sets the pace. Reduced glutathione donates electrons to neutralize peroxides through glutathione peroxidase, a selenium enzyme, and is regenerated from its oxidized form. In the liver it conjugates drugs and toxins for excretion, which is why acetaminophen overdose, by exhausting glutathione, destroys liver cells, and why NAC is the antidote.
Swallowed glutathione is broken down by intestinal enzymes. A single 3 g dose did not raise plasma glutathione (Witschi 1992), and 500 mg twice daily for four weeks changed neither glutathione status nor oxidative stress markers (Allen 2011). Longer use may be different: 1,000 mg a day for six months raised glutathione in blood, red cells, and cheek cells by about 30% in a placebo-controlled trial, and levels returned to baseline after stopping (Richie 2015). A liposomal product raised body stores within two weeks in an open-label pilot of 12 adults (Sinha 2018).
The precursor route is better supported. NAC supplies cysteine directly, and in older adults with low glutathione, NAC plus glycine restored synthesis (Sekhar 2011). Intravenous glutathione is used in some clinics; in a small placebo-controlled trial in Parkinson's disease it gave no significant benefit (Hauser 2009).
Forms and Bioavailability
Absorption ratings are broad tiers. Head-to-head human trials rarely support a finer ranking among well-absorbed forms.
| Form | Absorption | Typical dose | Cost | Labels |
|---|---|---|---|---|
| Reduced Glutathione (GSH)L-glutathione, Setria | LowLargely broken down by gamma-glutamyl transferase in the gut. Single doses do not raise plasma glutathione, though six months at 1,000 mg daily raised body stores in one trial. | 250-1,000 mg daily | Moderate | |
| Liposomal Glutathione | VariablePackaged in phospholipid vesicles to limit gut breakdown. A 12-person open-label pilot reported higher body stores within two weeks. | 500-1,000 mg daily | High | 3 |
| S-Acetyl GlutathioneSAG | VariableAcetylating the sulfur protects it from breakdown in cell studies; the acetyl group is removed inside cells. Human pharmacokinetic data are scant. | 100-300 mg daily | High |
Labels column: number of labels named as glutathione products that list this form. A product can list more than one form, and some labels do not state a form at all.
Reduced glutathione (GSH) is the standard oral form; Setria, a fermented GSH, was used in the six-month trial. Liposomal glutathione is packaged to limit gut breakdown, with pilot-level data. S-acetyl glutathione is protected against breakdown in cell studies, but human pharmacokinetic data are scant. Nebulized glutathione can cause bronchospasm in people with asthma (Marrades 1997).
Typical Dosing
Oral trials used 250-1,000 mg daily. NAC at 600-1,800 mg daily is the established way to supply cysteine, the amino acid that limits glutathione synthesis.
Food sources: asparagus, avocado, spinach, okra, fresh meat.
What to Look For
Start with NAC at 600 mg once or twice daily; it costs less and has more evidence. If you want glutathione itself, choose reduced glutathione at 500-1,000 mg daily and plan on months, not days, or a liposomal product if you accept its thinner evidence. Expect a sulfur smell from both.
Red flags: glutathione marketed for skin lightening, S-acetyl products claiming superior absorption without human data, and inhaled glutathione for anyone with asthma. Green flags: the form named, milligrams per serving, and third-party testing.
Reduced Glutathione (GSH)
The only form with a six-month controlled trial showing higher body stores, at 1,000 mg daily.
What to look for: Reduced glutathione or Setria, 500-1,000 mg daily, taken consistently.
Find on iHerb Affiliate linkLiposomal Glutathione
Faster rise in a small uncontrolled pilot, at a higher price.
What to look for: Milligrams of glutathione per serving stated, not just milligrams of liposomal liquid.
Find on iHerb Affiliate linkProducts on Titrate
884 of the 214,745 labels in the NIH Dietary Supplement Label Database list glutathione as an active ingredient (379 on market). 304 are sold as glutathione products by name.
Top on-market labels, ranked by label completeness and simplicity:
- Liposomal Glutathione
- Liposomal Glutathione
- Liposomal Glutathione
- L-Glutathione 100 mg
- Premier Glutathione Complex
Glutathione does not have its own search category yet. Each product above links to its full label in the NIH database.
Related Tools
References
Witschi A, Reddy S, Stofer B, Lauterburg BH. The systemic availability of oral glutathione. Eur J Clin Pharmacol. 1992;43(6):667-669.
Marrades RM, Roca J, Barberà JA, de Jover L, MacNee W, Rodriguez-Roisin R. Nebulized glutathione induces bronchoconstriction in patients with mild asthma. Am J Respir Crit Care Med. 1997;156(2):425-430.
Hauser RA, Lyons KE, McClain T, Carter S, Perlmutter D. Randomized, double-blind, pilot evaluation of intravenous glutathione in Parkinson's disease. Mov Disord. 2009;24(7):979-983.
Allen J, Bradley RD. Effects of oral glutathione supplementation on systemic oxidative stress biomarkers in human volunteers. J Altern Complement Med. 2011;17(9):827-833.
Sekhar RV, Patel SG, Guthikonda AP, et al. Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. Am J Clin Nutr. 2011;94(3):847-853.
Richie JP Jr, Nichenametla S, Neidig W, et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Eur J Nutr. 2015;54(2):251-263.
Sinha R, Sinha I, Calcagnotto A, et al. Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function. Eur J Clin Nutr. 2018;72(1):105-111.
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