Use, benefits, and side effects

N-acetylcysteine (NAC) is a supplement that has been available for several decades. People take it for various reasons, including to help treat medical issues ranging from psychological disorders to chronic lung conditions and to improve athletic performance.

Doctors believe that NAC may stimulate the synthesis of glutathione — a compound that helps fight free radicals, unstable atoms that can cause inflammation and damage.

Keep reading to learn how NAC may benefit the body. We also describe risks, including side effects, associated with the supplement.

Researchers have investigated the potential for NAC to help treat a wide variety of health issues. Some research indicates that NAC supplementation may help in the following ways.

Treating psychiatric conditions

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Increasing the amount of NAC in the body may boost levels of some neurotransmitters, and this may improve a person’s mental function.

According to a 2011 review, NAC may also help alleviate symptoms of various psychiatric conditions, including:

While research into NAC as a means of relieving psychiatric symptoms may be promising, most doctors would not recommend it as a sole treatment.

Instead, a person should rely upon evidence-based treatments, such as therapy and medication, when applicable. A doctor can provide advice about using NAC to supplement traditional treatment.

Treating lung conditions and excess mucus

For people with chronic lung conditions, such as bronchitis or cystic fibrosis, some doctors recommend NAC. It is available in an inhalable form that may help reduce excess mucus.

That said, clinical trials of NAC as a treatment for lung disease have arrived at mixed results, according to the Memorial Sloan Kettering Cancer Center.

Improving insulin sensitivity in people with PCOS

Authors of a 2017 review in Cell Journal concluded that taking NAC may benefit people with polycystic ovary syndrome (PCOS).

This syndrome can lead to insulin resistance and increases in blood sugar. The researchers reported evidence that NAC may help reduce high blood sugar in people with PCOS.

However, NAC is no substitute for medications such as insulin or other methods of blood sugar control. It may only be helpful as a supplement.

Reducing the risk of preterm birth

According to the same 2017 review, NAC supplements may help reduce the risk of preterm birth.

Infections such as bacterial vaginosis may increase the risk of preterm delivery, and the body’s inflammatory response may further raise the risk. Because NAC combats inflammation, the authors report, it may help counter this risk factor for preterm birth.

The authors refer to a study in which taking 0.6 grams of NAC per day, as well as progesterone, after 16 weeks of pregnancy helped prevent preterm delivery in women with histories of preterm delivery and bacterial vaginosis.

NAC may have a similar effect when a woman takes it in combination with folic acid, the authors report.

However, as with any supplement, it is important to consult a doctor about its safety before taking it during pregnancy.

Treating acetaminophen overdose

Doctors can use NAC to treat acetaminophen overdoses.

Acetaminophen is an analgesic that can relieve aches, pains, and a fever. If a person experiences an overdose of this drug, administering NAC within 10 hours may help reduce the risk of associated liver damage.

Other potential benefits

Some very small studies and case reports indicate that NAC may help with:

Preliminary studies in animals also demonstrate that NAC may help with heroin dependence and the adverse effects of alcohol consumption.

NAC is available over the counter in pharmacies and health stores.