What is Glutathione used for?

What it is being studied for

• Body glutathione stores, oral: in a 6-month human randomized trial of 54 adults (250 or 1,000 mg/day), glutathione rose 30–35% in red cells, plasma and lymphocytes, and 260% in cheek cells at the higher dose; levels returned to baseline a month after stopping [1].
• Body stores, liposomal oral: a 1-month pilot in 12 healthy adults reported up to +40% in whole blood and +100% in white blood cells at 2 weeks; a small human study with no control group described in the abstract [2].
• Single oral dose: in 7 healthy volunteers, one 3 g dose did not significantly raise plasma glutathione over 270 minutes; the authors concluded systemic availability was negligible (human single-dose study) [3].
• Under the tongue vs swallowed: a 3-week human randomized crossover trial in 20 people with metabolic syndrome found the sublingual form raised the reduced-to-oxidized glutathione ratio more than oral glutathione or N-acetylcysteine (p=0.003) [4].
• Skin lightening, oral: a human randomized trial of 60 students (500 mg/day, 4 weeks) found the melanin index fell more than placebo at two of six sites (face p=0.021, forearm p=0.036) [5]; a 12-week randomized trial in women reported melanin and UV spots only tending lower [6].
• Cystic fibrosis, inhaled: a 6-month human randomized trial (n=153) missed its primary lung-function endpoint and did not reduce flare-ups [7]; a 12-month randomized trial (n=105) also missed its primary endpoint, with gains only in moderate disease [8].
• Parkinson’s disease, nasal spray: a phase I/IIa randomized trial (n=30) met its tolerability endpoints [9]; a phase IIb randomized trial (n=45) found neither dose better than placebo, as all groups improved [10].
• Parkinson’s disease, intravenous: an open-label study of 9 untreated early patients reported a 42% decline in disability after 30 days; a human observational study with no control group [11].
• Heart attack (STEMI), intravenous: a 50-patient human randomized pilot gave glutathione around a stent procedure and measured oxidative-stress markers; the results were not read in full for this page [12].

How it works

1. Swallowed glutathione is broken down by gut and liver enzymes, which the authors gave as the reason a single oral dose did not raise blood levels [3].
2. Daily oral dosing over weeks to months still raised glutathione measured inside blood and cheek cells and lowered the oxidized-to-reduced ratio [1] [2].
3. Given into a vein, plasma glutathione rose about 50-fold, was cleared with a half-life of about 14 minutes, and raised plasma cysteine, one of its building blocks [13].
4. Immune readings moved in the oral studies: natural-killer-cell activity more than doubled at 3 months in the randomized trial [1] and rose by up to 400% in the pilot [2].
5. What sets it apart from N-acetylcysteine, a cysteine source given so the body makes its own glutathione: in a head-to-head crossover, the sublingual glutathione form shifted the blood glutathione ratio more than N-acetylcysteine did [4].

Adverse events reported

• Inhaled, asthma: nebulized 600 mg narrowed the airways in 8 people with mild asthma (lung function −19% vs −1% on placebo), with cough in 4 and breathlessness in 3 [14].
• Inhaled, cystic fibrosis: adverse-event rates were similar to placebo in one trial [7] and treatment was reported as well tolerated in the other [8].
• Nasal spray: no substantial difference from placebo over 3 months [9]; one participant on the higher dose developed cardiomyopathy in the phase IIb trial [10]; 12.1% of 70 survey respondents reported adverse effects [15].
• Oral: described by the authors as very well tolerated over 4 weeks, with long-term safety not established [5]; no serious adverse effects at 250 mg/day for 12 weeks [6].
• Intravenous: the abstracts read do not report adverse events either way [11] [12] [13].

Forms

Every form below has been given to people in a published study: oral capsules [1] [3], liposomal oral [2], sublingual [4], inhaled [7] [8], nasal spray [9] [10] and intravenous infusion [11] [13]. Most outcomes were blood glutathione levels or other markers rather than clinical events.

How the swallowed, under-the-tongue and injected forms compare in the trials: Glutathione oral vs injection.