You may have seen the acronym but wondered, “What is NAC?” It stands for N-acetyl cysteine (NAC), a form of the amino acid L-cysteine. NAC benefits both the brain and body, which is why it has been in use as a supplement for decades. In clinical trials, supplementation with NAC is effective for treatment of a variety of health problems.
Before looking at the multitude of NAC benefits, however, it’s useful to understand the three primary ways in which NAC exerts its actions.
NAC Benefits: The Big Three
Science has proven that N-acetyl cysteine helps us because it’s:
- An antioxidant. NAC is most well known for its antioxidant effects. While it can act as an antioxidant directly, NAC is remarkable in its ability to increase glutathione, the body’s most potent self-made antioxidant and detoxification compound. Glutathione is especially important for proper brain function, lung function, and liver detoxification processes. Our bodies make their own glutathione using the amino acid cysteine, but levels may be depleted in a number of health conditions. Because of glutathione’s chemical structure, it is not possible to take glutathione as a supplement and absorb it. However, studies show that taking the form of cysteine known as NAC as a supplement will raise glutathione levels within the brain and body tissues.
- Mucus-dissolving. Second, NAC supplements break up mucus, especially in the lungs and respiratory tract. Therefore, in addition to its glutathione-increasing effects, NAC is popular as a supplement for its “mucolytic” effects; it is able to break up or loosen sputum. making it easier to cough up. NAC does this by removing specific bonds in mucus proteins.
- A glutaminergic. Third, NAC is considered a “glutaminergic” compound, meaning it can modulate levels of glutamate, the most abundant excitatory neurotransmitter in the brain. Glutamate is involved in a broad range of learning, behavior, and memory. NAC, for example, has been shown to modulate the levels of excessive glutamate, which cause toxic damage in brain disorders like schizophrenia and addiction.
NAC Benefits for Lung and Respiratory Diseases
Glutathione is the primary antioxidant in the lungs. Because of NAC’s ability to break up mucus and its powerful antioxidant effects in terms of boosting glutathione, NAC has been studied as a natural remedy for lung and respiratory conditions like COPD, bronchitis, the flu, and more.
- Chronic bronchitis. In this respiratory disease, the mucus membrane in the lungs’ bronchial passages becomes inflamed, swelling and shutting off the tiny airways in the lungs. This leads to coughing spells that may be accompanied by phlegm and breathlessness. Smokers and people with asthma and COPD (see below) can be susceptible to chronic bronchitis. A review of almost 40 clinical trials of NAC found that it was safe and effective as a natural treatment for chronic bronchitis. How? It reduces exacerbation episodes of the disease, and because it helps reduce the viscosity (thickness) of sputum, NAC benefits patients’ ability to expectorate and to reduce the severity of coughs. In addition to helping break up mucus, NAC may reduce the elevated bacterial counts that are often seen in the lungs of some people, particularly smokers, with chronic bronchitis.
- Chronic obstructive pulmonary disease (COPD). COPD is a common but serious progressive lung disease that makes it hard to breathe and causes coughing that produces large amounts of mucus. Long-term high-dose NAC treatment can decrease COPD exacerbations, according to a recent meta-analysis of 11 studies evaluating NAC supplementation for COPD. In one recent study, treatment for one year with 600 mg NAC twice a day resulted in significantly improved lung function and decreased frequency of COPD symptom exacerbation in patients with stable COPD.
- Flu treatment and prevention. Taking NAC during the winter months may help prevent and treat flu-like symptoms. In one double-blind study in 262 adults, 600 mg NAC twice a day was well tolerated and resulted in a significant decrease in the frequency of influenza-like episodes, severity, and length of time confined to bed.
- Other respiratory conditions. In addition to bronchitis and COPD, there is some evidence that taking NAC as a supplement can be helpful for other conditions related to the lungs and respiratory tract, including cystic fibrosis, asthma, pulmonary fibrosis, and symptoms of nasal and sinus congestion due to allergies or infections.
HOW TO TAKE NAC SUPPLEMENTS
Don’t ignore the powerful NAC benefits for conditions characterized by excessive mucus, including many lung conditions, colds, flu, and allergies. Just as important are NAC’s remarkable effects on symptoms of many brain-related conditions, even addictions!
The optimal dose of NAC is 600 mg two to three times a day. Oral NAC supplements are safe and generally well tolerated, although they may infrequently cause diarrhea, nausea, and vomiting.
NAC Benefits for Nervous System and Mood Disorders
In addition to being of paramount importance in maintaining healthy lung tissue, glutathione is the principle antioxidant in the brain. NAC is also, as you learned above, able to modulate levels of the important neurotransmitter glutamate in the brain.
Both glutathione depletion and abnormal glutamate neurotransmission have been found in a number of mental health conditions and nervous system disorders, including bipolar disorder, schizophrenia, obsessive-compulsive disorder, pathological gambling, and cocaine dependence.
- Addictions. NAC supplement benefits include decreasing withdrawal symptoms and cravings and helping prevent relapse in cocaine addicts.[9,10] Preliminary studies indicate that NAC supplementation can also decrease marijuana and nicotine use and cravings.[11,12]
- Autism. Like addiction disorders, autism is a brain disorder in which there is an imbalance in the brain’s excitatory/inhibitory systems with abnormal regulation of glutamate. Imbalances in the brain’s antioxidant systems are also found in those with autism. Two published, double-blind, placebo-controlled studies have tested NAC supplementation in children with autism and both found that NAC significantly lessens the symptom of irritability.[13,14]
- Bipolar disorder. Glutathione levels are depleted in patients with bipolar disorder. By increasing glutathione, NAC can reduce depressive and manic symptoms in patients with bipolar disorder.[15-17]
- Other brain-related conditions. In addition to bipolar disorder, addictions, and autism, small studies have shown that NAC benefits symptoms of obsessive compulsive disorder (OCD), ADHD, schizophrenia, depression, Alzheimer’s, and Parkinson’s disease.
Have You Experienced the Amazing NAC Benefits?
If you’ve tried NAC and found it useful for your health condition, please tell us your story in the comments section below. Share your experience with the health benefits of NAC.
 Biochim Biophys Acta. 2013 Aug;1830(8):4117-29.
 Eur Respir J 2000;16:253-62.
 Clin Ther. 2000 Feb;22(2):209-21.
 Eur Respir J 1994;7:94-101.
 COPD. 2013 Dec 30. [Epub ahead of print]
 Chest. 2013 Jul;144(1):106-18.
 Eur Respir J. 1997 Jul;10(7):1535-41.
 Proc Natl Acad Sci U S A. 2006 Mar 21;103(12):4628-33.
 Neuropsychopharmacology. 2012 Aug;37(9):2143-52.
 Am J Addict. 2006; 15(1): 105–110.
 Am J Addict. 2010 March 1; 19(2): 187–189.
 CNS Drugs. 2014 Feb;28(2):95-106.
 Biol Psychiatry. 2012 Jun 1;71(11):956-61.
 BMC Psychiatry. 2013 Jul 25;13:196.
 BMC Med. 2012; 10: 91.
 Aust N Z J Psychiatry. 2013 Jun;47(6):564-8
 Rev Bras Psiquiatr. 2011 Dec;33(4):374-8.
 Trends Pharmacol Sci. 2013 Mar;34(3):167-77.
Originally published in 2014, this post is regularly updated.