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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.

This article discusses how NAC may benefit the body. It also describes the risks and 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

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

According to a 2018 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 suggested 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, high-quality studies have not directly examined this.

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 2009 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 people with histories of preterm delivery and bacterial vaginosis.

NAC may have a similar effect when a person 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 NAC during pregnancy.

Treating acetaminophen overdose

Doctors can use NAC to treat acetaminophen overdoses.

Acetaminophen is an analgesic that can relieve aches, pains, and 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

Several studies indicate that NAC may help with:

In addition, recent research has shown that NAC may help suppress SARS-CoV-2, the virus that causes COVID-19. In particular, it may help reduce a patient’s need for mechanical ventilation, as well as mortality. However, there is currently limited evidence for these effects.

NAC is available over the counter in pharmacies and health stores. The Food and Drug Administration (FDA) is currently reviewing whether dietary supplements should continue to contain NAC since it has already approved the substance as a drug.

The body needs 20 amino acids to maintain normal function. Of those, the body can make 11 by itself, which means a person does not need to eat in order to get them. L-cysteine is one of these amino acids.

In the body, NAC converts to l-cysteine, a nonessential amino acid. The body then uses l-cysteine to make glutathione, which is a tripeptide or chain of amino acids composed of cysteine, glycine, and glutamic acid.

Glutathione is an antioxidant with important functions in the body, such as making DNA, supporting the immune system, supporting the function of specific enzymes, helping certain organ functions, and more.

Scientists believe that the supply of l-cysteine in the cell limits the rate of glutathione production in the body. So, increasing l-cysteine supply can increase this rate. NAC may be less toxic and more soluble than l-cysteine itself, which is why NAC is often used in supplements instead of l-cysteine by itself.

A common dose of NAC is 600–1,200 mg per day. However, people should discuss the use of NAC and precise dosage with a physician.

At least one clinical trial has looked into whether NAC can help children with OCD. Still, current guidelines say that children under the age of 12 should not take NAC.

The body can convert NAC to l-cysteine. Alternatively, people can obtain l-cysteine from foods that contain protein.

Protein-rich foods include:

The side effects of NAC supplementation are usually mild and may include:

Very rarely, people have reported more severe side effects, such as low blood pressure, asthma attacks, and unexplained headaches.

People taking nitroglycerin in pills, patches, or creams should not take NAC, as the combination could cause extremely low blood pressure and headaches.

NAC is an antioxidant that may reduce inflammation. Taking it as a supplement may help improve symptoms of a number of medical conditions.

However, it is crucial to note that most research into NAC supplementation has taken place on a small scale. Determining the extent of the supplement’s benefits will require further research.

Anyone who wishes to try NAC supplements should consult a doctor first.

NAC is available for purchase online.