N-Acetyl Cysteine (NAC)
The most direct glutathione precursor. Hospital-grade antioxidant used for acetaminophen overdose, with emerging uses in mental health, fertility, and longevity.
Rock solid as acetaminophen antidote (clinical standard). Strong evidence in COPD (mucolytic, exacerbation reduction), fertility (male sperm parameters, PCOS in women), OCD, trichotillomania, and infertility-related PCOS. Liver protection well-established. Effects on mucus / breathing: days. Mental health: 8–12 weeks. Longevity markers: 16+ weeks.
NAC is a modified form of the amino acid cysteine that crosses cell membranes well and is rapidly converted to glutathione — the body's master antioxidant. In hospitals it's the antidote for acetaminophen overdose (gives the liver enough cysteine to regenerate glutathione faster than the toxin destroys it). Outside the ICU, NAC has gathered evidence in psychiatry (OCD, trichotillomania, addiction), respiratory disease (mucolytic — thins mucus), fertility (sperm quality, PCOS), and longevity (paired with glycine in the GlyNAC protocols). The FDA has wobbled on its supplement status in the US over the years but it remains widely available.
- Form
- Plain N-Acetyl Cysteine capsules. Effervescent NAC (hospital form, dissolves in water) for mucolytic use. NAC + glycine (GlyNAC) for longevity protocols.
- Dose
- 600–1,200 mg/day for general antioxidant / glutathione support. 1,800–2,400 mg/day for psychiatric or COPD use (split AM/PM). 600 mg twice daily is the most common starting point.
- Timing
- Empty stomach for best absorption; or with food if it causes GI upset. AM/PM split for higher doses.
- Schedule
- Daily. Some users cycle to avoid theoretical receptor desensitisation but evidence for this is thin.
- Side effects
- Sulfur smell (some products). Mild GI upset, nausea. Headache. Rarely, paradoxical bronchospasm in asthmatics — start cautiously.
- Interactions
- Nitrates / nitroglycerine — additive vasodilation, hypotension. Activated charcoal reduces NAC absorption. Some chemotherapy drugs — NAC may reduce efficacy (discuss with oncologist).
- Contraindications
- Active asthma exacerbation (bronchospasm risk). Bleeding disorders (mild antiplatelet effect at high doses).
- Lab markers
- Plasma glutathione (research-grade). Liver enzymes if monitoring hepatic effect. No standard NAC test.
- Food sources
- Cysteine (not NAC) is found in eggs, garlic, onions, broccoli, brussels sprouts, red peppers. The body converts cysteine to glutathione, but at a slower rate than NAC delivers.
Pairs with
Glycine — the GlyNAC longevity stack. Selenium (cofactor for glutathione peroxidase). Alpha-lipoic acid (regenerates oxidised antioxidants). Vitamin C and E (network antioxidants).
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