Is this the one supplement everyone should be taking?

By John Murphy
Published October 28, 2020

Key Takeaways

The nutritional supplement N-acetylcysteine is like the Swiss Army knife of supplements. It’s used to treat a wide range of health conditions, including allergies, Alzheimer disease, bipolar disorder, bronchitis, chronic kidney disease, cirrhosis, heart disease, hepatitis, infertility, schizophrenia, and upper respiratory infections. 

Then again, many dietary supplements are believed to have a variety of uses. The big question is whether they actually work. To answer that question, here’s some of the research that supports a few of the many uses of N-acetylcysteine.

What is N-acetylcysteine?

N-acetylcysteine is a precursor of the amino acid cysteine, which bonds with two other amino acids in the body—glutamate and glycine—to form the powerful antioxidant glutathione. 

Glutathione is found in high concentrations in most cells of the body. It regulates a range of cellular functions and immune responses. Glutathione neutralizes free radicals, detoxifies harmful compounds, directly scavenges oxidative chemicals, and targets the causes of oxidative stress. It also protects against oxidants by recycling vitamin C and vitamin E.

Because glutathione is involved in so many cellular activities and processes—and because N-acetylcysteine can increase the production of glutathione—researchers have been studying N-acetylcysteine for use in a wide variety of medical conditions. 

Acetaminophen toxicity

Acetaminophen is widely used and is generally considered safe. But overdosing can happen. In fact, acetaminophen toxicity causes 500 deaths per year, not to mention thousands of emergency department visits and hospitalizations. Acetaminophen toxicity is also the most common cause of liver transplantation in the United States.

N-acetylcysteine has been used for years as a reliable antidote to acetaminophen toxicity, administered either intravenously or orally. It’s believed to protect the liver by boosting glutathione levels, which deactivate toxic metabolites. 

N-acetylcysteine is most effective at reducing liver injury when administered within 8-10 hours of an overdose. This can bring down the rate of liver toxicity to about 3%. 


N-acetylcysteine is already used as a mucolytic for people with chronic obstructive pulmonary disease (COPD). Because of its antioxidant and anti-inflammatory properties, N-acetylcysteine is also being investigated as a direct therapy for COPD. In a large, randomized controlled trial published in The Lancet Respiratory Medicine, researchers showed that N-acetylcysteine 600 mg twice daily prevented acute exacerbations of COPD, particularly in patients with moderate disease. Other studies found that N-acetylcysteine improved pulmonary function and reduced hospital readmissions.

A large randomized clinical trial is now underway to determine the efficacy of N-acetylcysteine in patients with early-stage COPD. 

High blood pressure

N-acetylcysteine has been shown to lower blood pressure. In a study reported in the American Journal of Clinical Nutrition, a 4-week treatment of 1.8 g daily N-acetylcysteine in middle-aged men significantly lowered serum homocysteine—an independent risk factor for cardiovascular disease. The treatment also significantly decreased both systolic and diastolic blood pressure in all individuals, with a significant reduction of diastolic blood pressure in those with hyperlipidemia.


There is no single effective treatment for polycystic ovary syndrome (PCOS), but N-acetylcysteine may be able to help, according to a study published in Obstetrics and Gynecology International. In this meta-analysis of eight randomized clinical trials involving 910 women with PCOS, researchers found that women who took N-acetylcysteine had higher odds of ovulating, getting pregnant, and having a live birth compared with those taking placebo. However, N-acetylcysteine had no effect on rates of miscarriage, menstrual regulation, acne, hirsutism, body mass index, testosterone, insulin levels, or adverse events.


Oxidative stress is believed to play a central role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), so researchers have studied antioxidants for treating these patients. For instance, a randomized trial of 30 people with NAFLD showed that a 3-month regimen of N-acetylcysteine 600 mg twice daily lowered levels of ALT (alanine transaminase) and decreased the size of the spleen compared with participants taking vitamin C. 


N-acetylcysteine is one of the many agents researchers are investigating as a treatment for COVID-19. As noted in the beginning of this article, N-acetylcysteine boosts levels of glutathione, which decreases the production of proinflammatory cytokines. Given this, researchers hypothesized that early administration of antioxidants such as N-acetylcysteine could be used to combat the cytokine storm that presages acute respiratory distress syndrome (ARDS) in COVID-19 patients. 

Other researchers have found that N-acetylcysteine has antiviral activity against a number of viruses. They noted that increased levels of glutathione reduce viral load by inhibiting viral replication, notably in H3N2 and H5N1 strains of influenza A. However, this indicates that N-acetylcysteine’s efficacy against viruses depends on the particular strain it faces. 

But wait, that’s not all

Three other important benefits of N-acetylcysteine are that it’s widely available over the counter, it’s inexpensive, and it’s safe and well-tolerated. 

Although N-acetylcysteine needs large clinical trials to really confirm whether it improves many of these conditions, it continues to be investigated for a myriad of health problems. Some of these include dermatologic conditions, neurodegenerative conditions like Alzheimer disease and dementia, and psychiatric disorders like obsessive-compulsive spectrum disorder and bipolar disorder. It’s also shown some promise in post-traumatic stress disorder and substance use disorders.

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