NAC (N-acetyl cysteine) is an altered form of the amino acid cysteine, which is commonly found in food and synthesized by the body.
Where is it found?
Cysteine, the amino acid from which NAC is derived, is found in most high-protein foods. NAC is not found in the diet.
NAC has been used in connection with the following conditions (refer to the individual health concern for complete information):
| Science Ratings | Health Concerns |
|---|---|
 |
Acetaminophen poisoning Bronchitis (chronic) |
 |
Heart attack (IV immediately following a myocardial infarction) Prevention of kidney damage during coronary angiography Unverricht-Lundborg disease |
 |
Pseudoporphyria |
| Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, little scientific support and/or minimal health
benefit. |
|
Who is likely to be deficient?
Deficiencies of NAC have not been defined and may not exist. Deficiencies of the related amino acidcysteine have been reported in HIV-infected patients.1
How much is usually taken?
Healthy people do not need to supplement NAC. Optimal levels of supplementation remain unknown, though much of the research uses 250–1,500 mg per day.
Are there any side effects or interactions?
One study reported that 19% of people taking NAC orally experienced nausea, vomiting, headache, dry mouth, dizziness, or abdominal pain.2 These symptoms have not been consistently reported by other researchers, however.
Although a great deal of research has shown that NAC has antioxidant activity, one small study found that daily amounts of 1.2 grams or more could lead to increased oxidative stress.3 Extremely large amounts of cysteine, the amino acid from which NAC is derived, may be toxic to nerve cells in rats.
NAC may increase urinary zinc excretion.4 Therefore, supplemental zinc and copper should be added when supplementing with NAC for extended periods.
Are there any drug
interactions?
Certain medicines may interact with N-Acetyl Cysteine. Refer to drug interactions for a list of those medicines.
1. De Quay B, Malinverni R, Lauterburg BH. Glutathione depletion in HIV-infected patients: role of cysteine deficiency and effect of oral N-acetylcysteine. AIDS 1992;6:815–9.
2. Tattersall AB, Bridgman KM, Huitson A. Acetylcysteine (Fabrol) in chronic bronchitis—a study in general practice. J Int Med Res 1983;11:279–84.
3. Kleinveld HA, Demacker PNM, Stalenhoef AFH. Failure of N-acetylcysteine to reduce low-density lipoprotein oxidizability in healthy subjects. Eur J Clin Pharmacol 1992;43:639–42.
4. Brumas V, Hacht B, Filella M, Berthon G. Can N-acetyl-L-cysteine affect zinc metabolism when used as a paracetamol antidote? Agents Actions 1992;36:278–88.
