N-ACETYL CYSTEINE (NAC): Overview & Uses

N-acetyl cysteine, or NAC, is one of those supplements that the majority of people could potentially benefit from using. NAC comes from L-cysteine, an amino acid. An amino acid is a protein building block.

N-acetyl cysteine is an antioxidant, and it’s thought to have a role in the prevention of cancer. It’s also used in medical settings to treat acetaminophen overdose (Tylenol) because it binds to the active ingredient in the liver. In medical settings, it’s most often intravenous n acetyl cysteine that’s used. Some of the reasons people supplement with it include helping with lung conditions, respiratory conditions, and coughing. It’s also used for dry eye, the flu, and a variety of other conditions.

This amino acid has powerful antioxidant properties to scavenge and destroy reactive oxygen species that are at the core of many chronic health conditions.

For a period of time, NAC wasn’t available on Amazon and some other retailers at the request of the FDA, which we’ll talk more about later.

Some of the things that it’s probably most beneficial for include acetaminophen poisoning, complete or partial lung collapse, preparing for lung tests, and caring for people who have a tube in their windpipe. These are scenarios where a healthcare provider would give the product on a prescription basis, although you can buy it supplementally.

N-Acetyl Cysteine: NAC Supplements for Many Conditions

An NAC supplement is a synthetic form of cysteine. Cysteine is a nonessential amino acid or a semi-essential amino acid, so your body produces some of what you need, and you get the rest from food or supplements.

Your body can produce it from other amino acids, so that’s why it’s sometimes categorized as semi-essential. The amino acids your body can use to produce it include serine and methionine. When your dietary intake of these amino acids is low, then it becomes essential.

Cysteine is found in foods high in protein, like chicken, turkey, cheese, eggs, and legumes.

One of the unique factors of NAC that you don’t always see with supplements is that it’s approved by the Food and Drug Administration for some uses.

Some of the benefits of the amino acid could stem from its ability to replenish glutathione levels in the body.

The primary role of NAC is linked to its anti-inflammatory and antioxidant activities. Because of those effects, there’s a lot of investigation and research into the therapeutic potential of the amino acid for conditions that are related to oxidative stress.

In animal studies, NAC has shown a strong protective effect against oxidative stress and inflammation in a variety of conditions, including brain damage from transient cerebral ischemia and pain and inflammation during infections. Animal studies have also shown benefits for thyroid health through the reduction of inflammatory cells.

Is NAC a Drug or a Supplement?

For decades, NAC has been available as a dietary supplement, but there’s a lot of confusion between companies marketing it as such and the FDA. It was initially approved by the FDA as a respiratory drug in 1963. It’s also used in medical settings as a prescription drug to prevent serious liver damage when someone experiences acetaminophen poisoning.

Following the pandemic, COVID claimed that there was no evidence NAC was used as a supplement before it was approved to be used as a drug. That was their rationale as to why marketing NAC as a supplement would be illegal.

There were several supplement companies that received warning letters from the FDA about making claims that NAC could help with hangovers. The FDA, at the same time, flagged the companies for using NAC in products.

As of August 2022, the FDA has started moving away from its hardline stance, and it has since said it’s considered a rule allowing the sale of NAC as a dietary supplement. The product has been available on Amazon once again after they were pulled, and it’s currently very easy to find.

NAC is widely used to treat acetaminophen overdoses and as a mucolytic compound for the treatment of respiratory diseases.

The Food and Drug Administration and the World Health Organization (WHO) recognize it as an essential drug.

What Are the Benefits of NAC?

Below, we go over some of the more specific benefits of n acetyl cysteine and what we currently know.

May Help Improve Certain Mental Health Conditions

NAC is a fascinating amino acid and supplement, and one of the most compelling areas of interest in research is how it can benefit psychiatric and mental health conditions.

There are studies showing NAC can help with conditions like anxiety, depression, and obsessive-compulsive disorder (OCD).

In early research, NAC has been found to balance glutamate levels, boost new brain cell growth and reduce inflammation. These are three ways it might help depression. In people with depression and mood disorders, after three to four months, in some cases, it’s led to improvements.

Currently, NAC is being researched for its ability to help with symptoms of bipolar disorder, and since it can balance glutamate and improve antioxidant status in the brain, it may also help OCD.

In early studies, NAC has shown promise to help with some of the symptoms of autism—for example, in a study of children with autism, three months of supplementing with the amino acid led to reduced irritability.

There are preliminary studies of NAC’s effects on schizophrenia, showing that it might help improve symptoms perhaps by balancing glutamate levels in the brain and reducing inflammation and oxidative stress.

In older populations of people dealing with cognitive impairment or neurogenerative diseases, NAC may improve cognition.

There’s preliminary research currently ongoing that’s looking at the effects of supplementing with the amino acid to help with the cognitive deficits associated with Alzheimer’s and Parkinson’s.

NAC may, according to some early studies, help with compulsive symptoms that come along with multiple psychiatric conditions, and some researchers theorize it could help with addictive behaviors.

For example, a large-scale review of nine studies found that NAC could be possibly effective for treating cocaine and cannabis addictions. The study’s authors also suggested that there was the potential it could help with other types of addictions like methamphetamine, nicotine, and compulsive gambling, but there’s limited research in these areas.

The effects of glutamate are perhaps one of the most important things to understand when it comes to the mental health and psychiatric benefits of NAC.

Glutamate is the most abundantly present excitatory neurotransmitter that the nerve cells in our brains release. Glutamate plays a role in memory and learning, and we need the right amount at the right time for our brains to function optimally. When someone has too much glutamate, it’s associated with Huntington’s disease and Alzheimer’s.

Glutamate is required to make gamma-aminobutyric acid in the brain (GABA), which is the calming neurotransmitter that helps regulate sleep and anxiety, as well as muscle function.

Glutamate also acts as an amino acid, and it’s our body’s most abundant.

Other conditions associated with too much glutamate include Lou Gehrig’s disease, multiple sclerosis, stroke, chronic fatigue, and fibromyalgia.

Mood and mental health problems associated with the production of too much glutamate include anxiety and mood disorders, autism, depression, obsessive-compulsive disorder, and schizophrenia. If you have too little glutamate, it can cause mental exhaustion, low energy, problems with concentration, and insomnia.

N-acetylcysteine is thought to modulate glutamate dysfunction.

May Help Relieve Respiratory Disease Symptoms and Improve Lung Function

There are a number of ways these amino acid dietary supplements can help respiratory disease symptoms, and it’s one of the most studied areas for this amino acid. One way it helps treat respiratory issues is by breaking up mucus, helping conditions like chronic obstructive pulmonary disease, and helping lung function.

NAC supplements can also protect the lungs and airways that make up our respiratory tract.

According to clinical studies, NAC supplements can help with the treatment or prevention of chronic bronchitis and acute respiratory distress syndrome. Acute respiratory distress syndrome, or ARDS, is a potentially deadly complication that can occur with severe lung infections and pneumonia.

 When the lungs are healthy and working as they should, they have a built-in system for cleaning and protection. Small amounts of mucus are secreted, coating the airway walls. The mucus can trap particles that are inhaled, which can be infectious, irritants, or something worse. Conditions, including allergies, lung diseases, and infections, can cause dysfunction of the system. That then causes large amounts of mucus to be secreted.

If there’s an accumulation of too much mucus, it gets sticky, and it’s hard to remove, causing breathing difficulties. That can complicate lung conditions like bronchitis, asthma, emphysema, cystic fibrosis, and lung infections.

Doctors have been using inhaled forms of N-acetyl-L-cystine since the 1960s to help break down secretions of mucus, so they’re less sticky and dense. NAC can thin the mucus, and it helps clear airways, making it easier for cilia to sweep away the mucus and particles that become trapped. Cilia are tiny hair-like projections that are on the cells’ surface, lining the airways.

NAC is also a glutathione precursor. Glutathione reduces tissue damage from free radicals and oxidative stress. When someone takes oral NAC, it’s absorbed quickly and then distributed throughout their body, helping facilitate their body’s own production of glutathione.

Along with helping make glutathione, NAC is also a direct antioxidant.

Oxidative stress is one of the main causes of a lot of respiratory disorders, including COPD, infections, and lung problems that make it hard to breathe.

Emphysema is a good example. Oxidative stress in the lungs leads to inflammation, fluid in the lungs, too much mucus production, abnormal airway constriction, and tissue damage. NAC can reduce oxidative stress and the damage it contributes to while simultaneously reducing the volume and thickness of mucus.

NAC supplements may help the lungs in even more ways as well.

It can reduce the number of bacteria and viruses present, and in the case of bacteria, it can make it hard to cause an infection. In vitro studies have shown NAC can help prevent bacteria from sticking to the cells that line the airways by disrupting biofilms. Biofilms are slimy coverings that bacteria form around themselves. These biofilms prevent the immune system from being able to recognize and then access the bacteria. They also make it hard for antibiotics and antibodies to reach the bacteria.

NAC can block biofilm formation, and destroy ones that already exist, making it difficult for bacteria to survive in the airways.

This protection is also thought to extend to viruses. NAC might be able to block viral reproduction.

Specifically, respiratory conditions that N-acetyl-L-cysteine has been shown to be helpful for include:

• Chronic bronchitis is ongoing airway inflammation caused by irritation and damage to tissues. It’s common in people who smoke but can also be caused by inhaled irritants like pollution and secondhand smoke. NAC can significantly improve symptoms and reduce flare-ups of chronic bronchitis.
• Chronic obstructive pulmonary disease, or COPD are lung disorders that restrict airflow, making breathing hard. This can include chronic bronchitis, severe asthma, and emphysema. NAC can help with oxidative stress, excessive mucus secretion, and inflammation, which play major roles in these conditions. NAC has been shown to lead to clinical improvements in COPD patients.
• Acute respiratory distress syndrome, or ARDS, is severe lung inflammation that leads to fluid leaking into the lungs and that prevents oxygen from getting to the body. Animal studies show NAC can protect your lungs from injury and may lead to significant improvements. For example, in clinical studies, patients with ARDS given NAC had shorter stays in intensive care units and clinical improvements.

Liver and Kidney Health

Again, so many of the powerful benefits of NAC stem from the fact that it can restore your cellular levels of glutathione, which is your body’s detoxifier and antioxidant.

If you have an inflamed or fatty liver, glutathione can protect it and help to heal it. When someone experiences chronic liver inflammation, it depletes glutathione levels. Autoimmune diseases and problems with the immune system can cause low levels of glutathione, that’s bad for your liver and can worsen inflammation.

NAC is ultimately the most effective way to raise your body’s glutathione levels.

This amino acid supports your body’s natural detoxification pathways and promotes liver health.

Along with supporting the natural detoxification of the liver, NAC can also help detoxify your kidneys. It can alleviate the side effects of certain drugs and also help with environmental toxins. For example, if you’re exposed to heavy metals, it can affect the function and health of your liver and kidneys, but NAC can help detoxify these environmental substances.

Immune Health

When you take NAC supplements because of their ability to help you produce more glutathione, it can improve your immune health. Glutathione deficiency is thought to be associated with immune system function.

In two separate studies of people with HIV, NAC supplementation led to significant increases in immune function, and people’s natural killer cells were almost entirely restored.

In other situations involving a compromised immune system, like the flu, NAC, as mentioned, might help prevent the virus from replicating, which can help reduce symptoms and illness duration.

In older studies done in test tubes, NAC has been associated with blocking the replication of cancer cells and the death of cancer cells.

Heart Health

There are a few different ways NAC can help cardiovascular health and improve symptoms of conditions like acute myocardial infarction.

First, since it is a powerful antioxidant, it can protect the body from free radical damage. That can include damage that could affect the heart. Cardiovascular disease processes often involve the oxidation of LDL cholesterol. This is a process of the generation of free radicals because of a lack of antioxidants. Due to the deficit of antioxidants, blood vessel walls can get damaged, or they can narrow, and that can reduce blood flow, increasing artery pressure. That can lead to hypertension.

As we age, it affects our body’s ability to neutralize free radicals, so supplementing with antioxidants can help.

Another way the amino acid plays a role in heart health is because it protects the mitochondria, which produce energy in each of our cells. Our heart, as well as our brain and liver, consume significant amounts of energy, so they have more mitochondria than other tissues in the body.

If the mitochondria don’t have NAC, they can start to dysfunction. That can lead to chronic diseases. In one study, combining NAC with vitamin C and selenium helped to improve mitochondria function in rats with cardiac hypertrophy, which is an enlargement of the heart.

Taking NAC can help keep homocysteine levels down, and homocysteine is a substance that, when levels are high in the blood, can be a risk factor for sudden heart events.

NAC can improve circulation by increasing nitric oxide production, which means more circulation to and from the heart, which might also reduce the risk of experiencing a heart attack.

Yet another way NAC supplementation can help heart health is because of its effects on platelet aggregation. Platelet aggregation is the blood platelet’s natural ability to stick together when needed to prevent excess blood loss. However, when the blood coagulates too much or too often, specifically when platelets are too sticky, it can trigger a blockage in your circulatory system. The blockage can lead to a blood clot, and that can lead to a stroke, heart attack, or thrombosis of the leg. NAC seems to have an anti-aggregation effect on platelets potentially because it can help increase nitric oxide levels in the platelets themselves.

Stabilizing Blood Sugar

When you have high blood sugar and obesity, it can cause fat tissue inflammation. That can then destroy or damage insulin receptors, increasing the risk of type 2 diabetes. In studies, NAC has shown the ability to stabilize blood sugar through decreased inflammation in fat cells. That can, in turn, improve insulin resistance.

When you have healthy, intact insulin receptors, they remove sugar from your blood the way they should, so your levels stay in check.

Benefits for PCOS

Polycystic ovary syndrome, or PCOS, affects a growing number of women, but NAC supplementation might help some of the key symptoms of PCOS, including:

• Boosting fertility. Around 70% of women who have PCOS also experience infertility. A 2015 systematic review and meta-analysis found that NAC led to significant ovulation improvements and higher pregnancy and live birth rates compared to just a placebo. There’s some evidence to suggest NAC has benefits similar to the prescription drug metformin for improvements in pregnancy rate, improving menstrual regularity, and spontaneous ovulation.
• As mentioned earlier, NAC can help protect your insulin receptors and improve the activity of insulin receptors, which can then improve insulin resistance.
• NAC supplements might help with the restoration of hormonal balance. A 2019 study published in The Journal of Obstetrics and Gynecology of India found that compared to metformin, a group of women with PCOS taking NAC showed better improvements in hormonal profiles and their metabolic profiles, including a more significant reduction in total testosterone levels.
• Women with PCOS have higher levels of oxidative stress than women without this condition, and that promotes inflammation and damages cells. Since NAC is a powerful antioxidant, it can reduce oxidative damage and inflammation.
• NAC is great for liver health, and nonalcoholic fatty liver disease is often an associated complication of PCOS, likely because of high triglyceride and insulin levels.

Can Help Support Pregnancy Outcomes and Female and Male Infertility

N-acetyl-cysteine has possible benefits for both male and female fertility.

For males, research shows it can support fertility by reducing oxidative stress that can be damaging to sperm. In men with fertility issues, the sperm are often found to have higher levels of reactive oxygen species (ROS). That leads to dysfunctional sperm as well as DNA damage to sperm and reproductive problems.

In studies, giving NAC to men with fertility problems leads to increased sperm count and motility, as well as improved abnormal sperm structure. It can also raise testosterone levels.

For female fertility, the benefits of NAC include:

• Protection of the ovarian follicles
• Increased ovulation in women with PCOS
• Improvements in successful birth outcomes in women with unexplained recurrent loss of pregnancy when combined with folic acid
• Reduced risk of preterm birth in women with bacterial vaginosis
• Supports healthy blood pressure in pregnancy

Risks, Side Effects, and Interactions

One of the great things about N-acetyl cysteine, aside from its many health benefits, is that it’s considered a safe supplement for most people. At doses of 1,200 mg twice a day or lower, it appears to be well-tolerated. At doses close to this, it’s rare to experience side effects, but if someone were to, they’re usually mild and might include flushing, stomach pain, nausea, vomiting, or diarrhea.

Much larger doses should only be used in a clinical setting for acetaminophen poisoning.

How to Use NAC Supplements

As is true with other amino acid supplements, you should try to take NAC on an empty stomach at least 30 minutes before you eat or wait until two hours after you eat. This will help avoid having it compete with protein for absorption.

Since NAC is a supplement, it’s not regulated by the FDA, and there aren’t standard dosages, but based on currently available research, you might consider the following:

• For COPD, take 600 mg before bed
• If you have a cough, take 600 two times a day
• For flu prevention, take 600 mg twice a day
• As an immune booster, you can use anywhere from 500-1800 mg a day
• To cleanse your liver or boost liver health, take a dose of 500 to 600 mg a day
• If you’re dealing with OCD, substance use disorder, or other mental health disorders, take 600 mg two to four times a day

Does NAC Have Any Drug Interactions?

If you take any prescription medications, you should always talk to your doctor before trying a new supplement. There are potential moderate interactions between NAC and blood thinners, some blood pressure medicines, and nitroglycerin. You should also stop NAC if you have any surgeries coming up in the next two weeks because it could increase your bleeding risk.

What’s the Best NAC Supplement?

I take NAC every day, and I’ve tried a couple of different brands and types. My favorites include: