N-Acetyl-Cysteine (NAC)
Also known as: NAC, N-acetylcysteine, acetylcysteine
An acetylated form of the amino acid cysteine that is the rate-limiting precursor for glutathione, the body's principal intracellular antioxidant. It is widely used in liver, respiratory, immune, and mood-support formulas and has a large clinical literature at 600–3,000 mg/day. Its regulatory status as a dietary ingredient in the US was questioned by FDA in 2020 but the agency has since indicated enforcement discretion.
Research summary
Supplies cysteine for glutathione synthesis, directly scavenges reactive species, and modulates glutamate signaling.
Dosage
Daily amounts, of compound.
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 600 mg | 600–1,800 mg | 3,000 mg | — |
600 mg once or twice daily is the consumer norm; psychiatric and respiratory trials used 1,200–3,000 mg/day in divided doses. Take with food to reduce nausea. Oral bioavailability is low but sufficient to raise cysteine and glutathione.
Source material: synthetic
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Strong sulfur (rotten-egg) odor and sour taste; capsules are the standard format and powders need aggressive flavoring. Hygroscopic and oxidizes over time, so use tight packaging.
Formulation notes
Paired with glycine (GlyNAC), milk thistle, and alpha-lipoic acid in liver and antioxidant formulas. Vitamin C is sometimes added to limit cysteine oxidation.
- NDI status uncertain
Sources
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