N-acetylcysteine
NAC (N-acetylcysteine) is a supplement and medicine form of the amino acid cysteine. The body uses it to make glutathione, an antioxidant, and hospitals use it as the antidote to acetaminophen overdose.
3 amino acids make up glutathione; cysteine is the one in shortest supply
In hospital the antidote to acetaminophen (paracetamol) overdose
In food · none; food supplies cysteine instead
- Made from Cysteine plus an acetyl group
- Best evidence Overdose antidote then fewer COPD flare-ups
- Mixed evidence Mental health OCD, addiction, bipolar depression
- Watch with Nitroglycerin headaches and low blood pressure
Sources: pharmacology textbooks, systematic reviews of clinical trials. Not medical advice.
NAC in Food
NAC is made in a lab; no food contains it. What food does supply is cysteine, the amino acid NAC turns into, as part of ordinary protein. The body can also make cysteine from methionine.
- Meat, poultry and fishthe largest everyday sources of cysteine
- Eggs and dairyegg white and whey protein are rich in it
- Beans, lentils, nuts, seeds and whole grainsplant sources, in smaller amounts per portion
- NAC itselfonly from supplements and medicines
What Is NAC (N-Acetylcysteine)?
NAC was a medicine long before it was a supplement. Its first use was as a mucus thinner: its sulfur group breaks the bonds that make mucus thick and sticky, so it was inhaled or swallowed to clear the airways. Its best-known use came later, in emergency rooms.
When someone takes too much acetaminophen (paracetamol), the liver turns the excess into a toxic compound. Glutathione normally neutralizes it, but an overdose uses up the liver's glutathione within hours and liver cells start to die. NAC supplies the cysteine the liver needs to rebuild glutathione fast. Given within about 8 hours of the overdose, it prevents most liver damage.
How NAC Raises Glutathione
Glutathione is a small molecule made of three amino acids: glutamate, cysteine and glycine. It is one of the cell's main defenses against oxidation and helps the liver clear drugs and toxins. Of the three building blocks, cysteine is usually the scarcest, so how much a cell can make depends mostly on its cysteine supply.
This is the idea behind NAC as a supplement: give the body extra cysteine in a form it can absorb and convert, and see if glutathione rises. In an overdose it clearly works. In healthy people with a normal protein intake, there is no good evidence that taking NAC brings a health benefit.
What Human Studies Show About NAC
Lungs: reviews of trials in chronic bronchitis and COPD found that NAC by mouth can modestly reduce how often symptoms flare up. Mental health: small trials in obsessive-compulsive disorder, trichotillomania (hair-pulling), cannabis and other addictions, and bipolar depression have given mixed results. Many other claims, such as easing hangovers, rest on little or no human data.
NAC as a Supplement and a Drug
The NAC in a supplement capsule is the same molecule hospitals and pharmacies use as a medicine. NAC is not a food. It has real drug effects and real interactions.
Common NAC Mistakes
Self-treating an overdose. Hospital treatment uses large, carefully timed doses and blood tests. A suspected acetaminophen overdose needs emergency care, never a supplement at home.
Confusing NAC with glutathione pills. They are different products. NAC is a building block the body uses to make its own glutathione.
Thinking a bad smell means a bad batch. The sulfur smell comes with the molecule.
NAC Supplements
Supplements are the only source of NAC outside a hospital or pharmacy, usually as capsules or effervescent tablets.
NAC Side Effects
- By mouthnausea, vomiting, diarrhea and a sulfur smell or taste
- Inhaledcan tighten the airways in people with asthma
- Pregnancyused in hospital for overdose; as a supplement, not enough is known
Medicines That Interact With NAC
- Nitroglycerin and other nitratesNAC can strengthen their effect, causing headaches and low blood pressure
Caltide does not total NAC yet. Sources: pharmacology textbooks, systematic reviews of clinical trials. Ask a doctor or pharmacist before combining a supplement with a medicine.
N-acetylcysteine Sources and References
The figures and claims on this page are checked against these sources.
Questions About N-acetylcysteine
NAC (N-acetylcysteine) is a slightly changed form of the amino acid cysteine, with an acetyl group attached. The body strips that group off and uses the cysteine, mostly to make glutathione, one of its main antioxidants.
No, NAC itself is not, but cysteine is. Protein foods such as meat, poultry, fish, eggs, dairy, beans and whole grains supply cysteine every day; NAC comes only from supplements and medicines.
It is the standard antidote for an acetaminophen (paracetamol) overdose. Given early, it refills the liver's glutathione, which neutralizes the toxic breakdown product of the drug and prevents liver failure.
It thins mucus, which is why it is used as a mucus-loosening medicine. Reviews of trials in chronic bronchitis and COPD found that taking it by mouth can modestly reduce flare-ups.
It supplies cysteine, the building block of glutathione that is usually in shortest supply, and it clearly does so in an acetaminophen overdose. Whether it raises glutathione enough to matter in healthy people has not been shown.
By mouth, mostly nausea, vomiting, diarrhea and an unpleasant sulfur smell. Inhaled NAC can tighten the airways in people with asthma.
Because of its sulfur. The thiol group that makes NAC useful is the same chemistry that gives rotten eggs and onions their smell. A faint sulfur smell is normal for NAC products.
It is being studied. Small trials in obsessive-compulsive disorder, hair-pulling (trichotillomania), addiction and bipolar depression have given mixed results, and none is strong enough to replace standard treatment.
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