N-Acetyl Cysteine (NAC)
The powerful antioxidant precursor to glutathione — the body's master antioxidant
Also known as: N-Acetylcysteine • NAC • Acetylcysteine
Overview
N-Acetyl Cysteine (NAC) is the supplemental form of the amino acid L-cysteine and serves as the rate-limiting precursor to glutathione — the body's most important endogenous antioxidant. Glutathione is present in every cell and is essential for detoxification, immune function, and protection against oxidative stress. NAC has been used in hospitals for over 50 years as the standard treatment for acetaminophen (Tylenol) overdose and as a mucolytic agent for respiratory conditions. Beyond these medical uses, NAC has shown remarkable benefits for mental health (OCD, addiction, depression), liver protection, fertility, and immune function. It is one of the most versatile and underappreciated supplements available.
Key Benefits
Glutathione Production & Antioxidant Defense
NAC is the most effective oral supplement for raising glutathione levels. Glutathione is the body's master antioxidant, present in every cell, and essential for detoxification and immune function. NAC supplementation has been shown to increase intracellular glutathione by 30-50% within weeks.
Liver Protection & Detoxification
NAC is the gold-standard treatment for acetaminophen overdose precisely because of its powerful liver-protective effects. It supports Phase II liver detoxification, protects against alcohol-induced liver damage, and may help with non-alcoholic fatty liver disease (NAFLD).
Respiratory Health
NAC is a potent mucolytic — it breaks down mucus by cleaving disulfide bonds in mucoproteins. It has been used for decades in hospitals for chronic bronchitis, COPD, and cystic fibrosis. A meta-analysis found that NAC reduced COPD exacerbations by 41% compared to placebo.
Mental Health & Addiction
Emerging research shows NAC's remarkable potential for mental health conditions. It modulates glutamate (the brain's primary excitatory neurotransmitter) and has shown benefits for OCD, trichotillomania, addiction (cocaine, cannabis, nicotine), bipolar disorder, and depression.
Dosage & How to Take
Most adults benefit from 600–1,800 mg daily in divided doses. Take on an empty stomach for best absorption. NAC can deplete zinc and copper with long-term use, so consider supplementing these minerals.
| Purpose | Dose | Notes |
|---|---|---|
| General antioxidant support | 600–1,200 mg/day | Divided into 2 doses |
| Respiratory health | 1,200–1,800 mg/day | Divided into 2-3 doses |
| Mental health support | 1,200–2,400 mg/day | Under practitioner guidance |
| Liver support | 600–1,200 mg/day | Consistent daily use |
Best Time to Take
Take on an empty stomach, 30 minutes before meals. Divide into 2-3 doses throughout the day for sustained glutathione support.
With or Without Food
Best absorbed on an empty stomach, but can be taken with food if GI discomfort occurs.
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| NAC Capsules | Good | Convenience, standard supplementation | Most common form. 600mg capsules are standard. Easy to dose. |
| NAC Powder | Good | Flexible dosing, cost-effective | Allows precise dosing. Has a strong sulfur taste. Mix with juice. |
| Sustained-Release NAC | Good | Steady glutathione levels | More consistent blood levels throughout the day. May reduce GI side effects. |
Side Effects & Safety
Common
- Nausea (especially on empty stomach at high doses)
- GI discomfort
- Sulfur-smelling breath or body odor
- Headache
Rare
- Allergic reactions (rash, bronchospasm — very rare)
- May deplete zinc and copper with long-term use
- Kidney stone risk (theoretical)
Contraindications
- Active peptic ulcer
- Asthma (inhaled NAC can trigger bronchospasm — oral form is generally safe)
- Bleeding disorders
Interactions
Charcoal can bind NAC and reduce its absorption. Separate by at least 2 hours.
NAC may enhance the vasodilating effects of nitroglycerin, potentially causing severe headaches and hypotension.
Synergistic antioxidant combination. Vitamin C helps recycle glutathione, enhancing NAC's effects.
Long-term NAC use may deplete zinc and copper. Consider supplementing these minerals if using NAC chronically.
Scientific Research
NAC for COPD Exacerbations
NAC supplementation reduced the frequency of COPD exacerbations by 41% compared to placebo, with the greatest benefit at doses of 1,200mg daily.
NAC for Mental Health Conditions
Systematic review of 5 RCTs found NAC significantly improved symptoms of depression, bipolar disorder, OCD, and addiction compared to placebo.
NAC and Glutathione Levels
Comprehensive review confirmed NAC as the most effective oral supplement for increasing intracellular glutathione levels, with benefits for oxidative stress, inflammation, and immune function.
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.