N-Acetylcysteine (NAC)

Overview

N-Acetylcysteine (NAC) is a stable form of cysteine, a sulfur-containing amino acid crucial for producing glutathione (GSH) — one of the body’s most powerful intracellular antioxidants.
Clinically, NAC has long been used to:

Neutralize acetaminophen (Tylenol) overdose (validated hospital use),
Loosen mucus in respiratory disorders (mucolytic action),
And more recently, to protect cells from oxidative stress and support metabolic longevity (the GlyNAC concept).

What the evidence shows

Area	Evidence level	Observed effects
Glutathione & liver detoxification	High	Effectively restores hepatic glutathione during acute oxidative stress.
Respiratory health (COPD, bronchitis)	Moderate to high	Reduces respiratory exacerbations and improves mucus fluidity.
Nervous system / mood	Low to moderate	Preliminary evidence for regulating glutamate and improving mental balance (OCD, schizophrenia).
Aging & inflammation	Preliminary	Shows mitochondrial protection and anti-inflammatory potential when combined with glycine.

Overall level: Moderate for cellular and antioxidant protection.
High for validated medical use (intoxication, COPD).

Mechanism of action

Glutathione precursor (GSH): provides cysteine required for synthesis → promotes hepatic detoxification and neutralizes free radicals.
Mucolytic effect: breaks disulfide bonds in mucoproteins → thinner, easier-to-clear mucus.
Neuroprotection: regulates brain glutamate levels, reducing neuronal excitotoxicity.
Cytoprotection: limits mitochondrial oxidative damage, promoting cellular longevity.

💊 Dosage & forms

Use	Typical dosage	Details
Respiratory support (COPD)	600 mg × 2/day	Clinically proven mucolytic efficacy
Antioxidant / glutathione	300–1200 mg/day	1–2 doses depending on tolerance
GlyNAC formula	600 mg NAC + 2–5 g glycine × 2/day	Restores glutathione and mitochondrial function
Typical trial duration	4–12 weeks	Gradual, dose-dependent effects

💡 Tip: NAC is best absorbed on an empty stomach or away from high-protein meals.

Useful synergies

Combination	Main benefit
NAC + Glycine (GlyNAC)	Increases glutathione and enhances mitochondrial and cellular health
NAC + Vitamin C / Selenium	Synergistic antioxidant and immune support
NAC + CoQ10	Strengthens mitochondrial protection
NAC + Magnesium / B6	Supports nervous system and metabolic balance

🟢 Proven benefits

Protects cells from oxidative stress.
Supports liver detoxification and glutathione balance.
Thins bronchial mucus and improves respiratory function.
Promotes healthy mitochondrial activity and potential anti-aging effects with glycine (GlyNAC).

🟡 What remains uncertain

Long-term GlyNAC efficacy on human longevity.
Direct impact on neuroprotection and chronic disorders.
Comparative absorption of oral vs liposomal NAC forms.

⚠️ Risks & interactions

Consult a healthcare professional if you have asthma, liver or kidney disease, or during pregnancy/breastfeeding.
High doses may cause nausea or allergic reactions.
Possible side effects: nausea, reflux, diarrhea, hives, or rare bronchospasm.
May enhance the effects of nitroglycerin and antihypertensive drugs.
Possible interactions with antioxidants, chemotherapies, or anticoagulants.

✅ Quality tips

Choose pure NAC (≥99%), free from artificial additives.
Avoid combining with megadoses of antioxidants unless supervised.
For long-term use, monitor liver and kidney function.
For best tolerance, split doses (morning/evening) with adequate hydration.

Sources

- https://ods.od.nih.gov/ - https://www.canada.ca/en/health-canada.html - https://pubmed.ncbi.nlm.nih.gov/33948287/ - https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011541.pub2/full - https://examine.com/supplements/n-acetylcysteine/

Cochrane — NAC and respiratory disease review
PubMed (PMID: 33948287) — NAC and human health
Examine.com — NAC and glutathione synthesis summary
NIH/ODS — N-Acetylcysteine overview
Health Canada — Natural Health Products database