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43 Health Benefits of NAC (N-Acetyl Cysteine) & Side Effects

Written by Ana Aleksic, MSc (Pharmacy) | Last updated:
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Ana Aleksic, MSc (Pharmacy) | Last updated:

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wellbeing

NAC (N-Acetyl Cysteine) is an antioxidant with numerous potential health benefits. It may help with mood disorders, sleep, infections, and inflammation. It boosts your glutathione levels and helps with most states of increased oxidative stress that underlie chronic health problems. Read on to uncover all its benefits, along with dosage and side effects.

What is NAC?

Your body uses NAC to make its own antioxidants. Medically, it is used to treat acetaminophen toxicity; it is almost 100% effective as long as it’s given within the first eight hours after overdose [1, 2].

For all other purposes, NAC is an unapproved supplement. Preliminary evidence may look promising (and in some cases, very promising!), but future studies may find that NAC is actually ineffective for some of these purposes.

It’s important to talk to your doctor before adding NAC to your health strategies, as it may have unexpected interactions.

Antioxidant

NAC (short for N-Acetyl Cysteine) is transformed into the amino acid cysteine in the body.

Why should you care about cysteine? For one, it is the most important amino acid (along with glycine and glutamine) for the formation of glutathione, the body’s strongest antioxidant [1].

In other words, if glutathione is “the mother of all antioxidants,” then cysteine would be the grandmother.

Since cysteine levels can determine how much and how fast glutathione is made, NAC is essential in replenishing levels of this antioxidant. Glutathione (reduced glutathione or GSH) removes free radicals from cells and activates detox pathways [3, 4].

Cysteine also contains sulfur, which is essential for glutathione to work. Aside from boosting glutathione, NAC can directly fight free radicals [1, 5].

Its antioxidant effects protect DNA, cells, tissues, and organs from damage, inflammation, and harmful substances. For this reason, its benefits range from brain protection to liver support to balancing mood. NAC can also break down and soften mucus, which can improve symptoms of lung diseases [6, 1].

Importantly, NAC has been thoroughly researched. The number of clinical, animal, and cell studies that explored the benefits of NAC are almost impossible to list. There are close to a thousand clinical trials of NAC alone!

However, while most studies on NAC have found at least marginal benefits, a lot have had mixed results. That’s why the FDA still considered the evidence insufficient to recommend NAC for most health conditions.

NAC is a well-researched amino acid with powerful antioxidant properties. It’s essential for the production of glutathione, the master antioxidant.

Snapshot

Proponents:
  • Powerful antioxidant
  • Provides the building blocks for glutathione
  • May protect the lungs, gut, brain, liver, and kidneys
  • May defend against toxins and pollutants
  • May help with obsessive-compulsive symptoms and addiction
  • May help prevent the flu
  • Biofilm disruptor
  • Potential to improve fertility
  • May help with many chronic health problems
CONs
  • Doesn’t taste good and can cause nausea
  • May affect bleeding
  • Many purported benefits are unproven

Potential Benefits of N-Acetyl Cysteine (NAC)

Note that in the list below, acetaminophen toxicity is the only FDA-approved use of NAC. If you suspect that you or someone you know has overdosed on acetaminophen, call poison control and seek medical attention immediately. Do not attempt to self-administer NAC.

If you want to incorporate NAC into your daily health routine, talk to your doctor first. They can help you identify any unexpected interactions with your existing medical prescriptions and other health strategies.

Though the preliminary evidence for many of these potential benefits is promising, no usage of NAC is FDA-approved except for treatment of acetaminophen toxicity.

1) Emergency Medicine

NAC has been studied a lot in the intensive care units, as a possible way to reduce organ damage before and after surgery. It helped protect the livers of 70 patients with lung disease, when given shortly before heart surgery [7].

It could help with heart attack complications, assisted breathing, abdominal surgery, and pancreatitis when used in the emergency case, before or after surgery [8, 9, 10, 11].

Emergency medicine relies on NAC to treat acetaminophen toxicity and for preventing organ damage before or after surgery.

Liver Damage from Acetaminophen Toxicity

N-Acetyl Cysteine has been used as an antidote to acetaminophen poisoning for over 50 years. It is almost 100% effective as long as it’s given within the first eight hours after overdose [2].

Common painkillers (such as Tylenol) contain acetaminophen, which can damage the liver and even cause liver failure at high doses. Acetaminophen is the most common cause of serious, sudden liver damage [12, 13].

NAC can safely prevent serious liver damage from acetaminophen and increase survival, according to several studies of over 400 patients [12, 14].

Sudden, life-threatening liver damage can also be caused by various drugs, toxins, or hepatitis.

NAC helped protect the liver in 80 such cases. Patients with liver damage from drugs experienced the best results [15].

NAC has been studied a lot in intensive care units, as a possible way to reduce organ damage before and after surgery [7].

2) Liver

NAC boosts glutathione, the highest amount of which is in the liver. This is why NAC is under investigation for its potential to protect the liver from inflammation, drug poisoning, and serious liver diseases.

If the liver is damaged, inflammation and oxidative stress always rise. There is some evidence that NAC may protect the liver by reducing inflammation and increasing antioxidant reserves.

NAC reduced liver damage in 85% of all cases, according to a large review. It could protect the liver from factors such as excessive alcohol and environmental pollutants [16].

NAC injections helped increase liver function better than glutathione in one study of 75 patients with Hepatitis B [17].

NAC may help repair severe liver damage and enhance liver detox. It increases glutathione in the liver and helps to prevent oxidative liver damage from toxins, drugs, and infections.

3) Oxidative Stress

Excessive oxidative stress can damage cells and underlies many chronic diseases, malnutrition, and toxin exposure. By replenishing glutathione, NAC may be able to protect cells and organs that are under oxidative attack [18].

In several studies, NAC increased antioxidant status after just 8 days. It also raised the levels and activity of glutathione and reduced oxidative damage markers by more than 30% [19, 5].

NAC could also increase red blood cells and markers of their function and size (erythropoietin, hemoglobin, hematocrit, MCV) [19, 5].

NAC vs. Glutathione

Oral glutathione has poor bioavailability, and taking NAC is one potential way to circumvent this. NAC increased glutathione levels and other antioxidants better than glutathione supplements when taken orally in a study of 20 people. But sublingual glutathione (which is not widely available) had stronger effects than either NAC or oral glutathione after 3 weeks [20].

In addition, liposomal glutathione is effective at raising bodily levels of glutathione. As of the publication of this article, no studies have been done comparing the bioavailability of NAC and liposomal glutathione [20].

NAC shields your tissues against free radicals by boosting glutathione and other antioxidants. It has better absorption and efficacy than oral glutathione supplements.

4) Toxins and Pollutants

By increasing levels of glutathione and combating oxidative stress, NAC may help protect the body from various toxins and pollutants.

Heavy Metals

According to some studies, NAC may be a safe remedy for chronic lead toxicity. It reduced lead levels and increased antioxidant enzymes in red and white blood cells in 171 workers exposed to lead after 3 months [21, 22].

The combination of NAC and zinc could also protect from mercury toxicity in rats, preventing the accumulation of mercury in the liver and blood. Clinical studies would need to confirm this effect [23].

Pesticides

NAC could help with pesticide poisoning by enhancing detox. NAC given to 30 people suffering from pesticide poisoning increased glutathione and reduced the need for additional treatments [24, 25].

NAC also reduced the damage from a very toxic pesticide (aluminum phosphide) in one study. It shortened the hospital stay, improved breathing, and increased survival in people exposed to these pesticides [26].

Diesel Fuel

Exposure to diesel fuel can cause serious blood vessel damage, even in healthy people.

Taking NAC with vitamin C before diesel fuel exposure protected the blood vessels in one study of 21 people [27].

Diesel fumes can also cause breathing problems and worsen asthma. NAC over 6 days protected the airways and improved asthmatic symptoms in 26 people exposed to diesel, reducing their need for asthma medications [28].

Silica

Silica is often found on construction sites and in agriculture. It can cause serious lung damage. In 96 people exposed to silica, NAC combined with an anti-inflammatory improved lung function, coughing, pain, and congestion [29].

Chemical Warfare

NAC improved breathing, cough, congestion, and lung function in 144 people with poisoning from a chemical warfare agent (mustard gas) [30].

Deadly Mushrooms

NAC could be a lifesaver in people who accidentally ingest Death Cap, the number one cause of fatal mushroom poisoning worldwide. When added to an anti-poisoning protocol, it boosted recovery and prevented liver failure [31].

Thanks to its potent antioxidant effects, NAC may be able to reverse the damage caused by heavy metals, pesticides, diesel fuel, silica, chemical warfare, deadly mushrooms, and other poisons.

5) Lung Disease

COPD

NAC is commonly used to reduce the inflammation and mucus in people with lung disease, such as chronic bronchitis or Chronic Obstructive Pulmonary Disease (COPD). It can break down mucus and replenish glutathione in the lungs, which reduces airway damage and breathing difficulties [32].

According to a large review, NAC improves symptoms and prevents disease worsening in people with chronic bronchitis with no side effects. It needs to be taken for at least 3 – 6 months, as 2 months of NAC did not improve COPD in one study [32, 33].

Combined with vitamin C, NAC increased the antioxidant and nutritional status in 79 people with COPD [3].

High doses over 1 year were safe and improved lung capacity and breathing in people with COPD in another study [34].

NAC can also be given alongside oxygen, the typical COPD treatment. In 45 patients, it could prevent oxidative damage that can result from long-term oxygen treatment [35].

People with chronic bronchitis or COPD may benefit from long-term NAC supplementation as it improves lung function, prevents disease worsening, and softens mucus.

Lung Damage and Infections

NAC will not have the same respiratory benefits in people with lung scarring or lung infections.

It had mixed effects on lung damage in two studies of 151 patients with a lung-scarring disease. In a smaller study of 28 patients, inhaled NAC could help those with milder forms of the disease. Oral NAC did not have the same benefits in the larger study [36, 37].

Short-term, NAC increased the level of vitamin C and antioxidant status in patients with a lung infection and scarring but didn’t improve lung function. It was given only for 30 days, which is probably not long enough to impact tissue regeneration [38].

Inhaled NAC also helped with airway infections in a study of 100 small children [39].

NAC has a mild beneficial effect on lung scarring and infections. Inhalation may be more efficient than oral treatment.

6) Flu

Since NAC decreases the body’s inflammatory response, it may help prevent the flu or reduce symptoms of a common cold.

In one study of 262 older people, NAC cut the risk of catching the flu by 54%. It could be especially helpful in the winter months when the flu season takes a hold [40].

NAC is also sometimes added to standard treatments of sinus inflammation and infections [41, 42].

In cells, NAC reduced replication of the flu virus. If the virus can’t replicate quickly, it’s easier to fight it off [43].

Doctors often add NAC to standard treatments of the flu and other respiratory infections. It may prevent virus spreading and cut the risk of catching the flu.

7) Polycystic Ovary Syndrome (PCOS)

Clomiphene citrate is considered the gold standard for helping women with PCOS achieve ovulation, but more than half of women don’t respond to it. NAC is being researched as a potential alternative, but the studies so far have mixed results [44].

In the largest study of NAC in 150 women with PCOS who previously didn’t respond to treatments, NAC added to clomiphene citrate improved the ovulation and pregnancy rates after just 5 days. Another study of over 100 women confirmed this [45, 46].

In 60 women with PCOS, NAC improved the quality of egg cells. It also increased embryo health during in vitro fertilization [47].

Women with PCOS often suffer from weight gain. NAC could improve metabolic symptoms in 46 women with PCOS better than metformin (an anti-diabetic drug). It helped reduce [48]:

  • Blood lipids
  • Fasting glucose
  • Insulin

NAC had similar benefits to metformin in a study of 100 women with PCOS. It reduced high testosterone, high insulin, irregular cycles, and BMI after 6 months. Unlike metformin, NAC also lowered total and LDL cholesterol [49].

NAC improved insulin sensitivity in another study of 31 women with PCOS over 5 – 6 weeks [50].

NAC alone did not help women with hard-to-treat PCOS in other studies. It possibly works better when combined with the standard drugs than when used as a stand-alone [44].

When added to standard treatment, NAC may help women with PCOS by improving their fertility, lipid profile, and blood sugar control.

8) Male Fertility

Aside from helping women with PCOS, antioxidant therapies like NAC may increase fertility in men [51].

Oxidative stress can damage the sperm’s DNA, which reduces fertility [52].

In 120 infertile men, NAC improved semen quality and antioxidant status after 3 months [53].

Some studies looked at the fertility benefits of NAC with other antioxidants, such as B vitamins, vitamin C and D. This combination improved the sperm count in those with low sperm count in a study of 42 men [54].

In a large study of almost 500 infertile men, NAC with selenium improved semen quality after 6 months [55].

Some men are “subfertile,” meaning that they’re less fertile than average without an obvious underlying cause. In 84 such men trying to conceive, a supplement combination with NAC (plus vitamins, zinc, fig extract, and vitamin E) increased their “fertility potential” and pregnancy rates [52].

The typical NAC dosage for improving fertility in these studies was 600 mg/day, but remember that there is no “correct” dosage of NAC for this purpose, as no studies have been conducted to find one.

NAC, in combination with other antioxidants, may boost sperm count, sperm quality, and fertility in men.

9) Chemotherapy and X-Ray Side Effects

Cisplatin is common chemotherapy that can damage the ears and kidneys. NAC ear injections prevented cisplatin damage and protected the ears in a study of 84 people [56].

NAC infusions could also reduce mouth ulcers and inflammation from chemotherapy in 80 people with leukemia [57].

Oral NAC protected from the side effects of chemotherapy on the brain in 14 people with colon cancer [58].

NAC and other antioxidants may prevent from x-ray radiation used to diagnose bone cancers. Combined with vitamin C, lipoic acid, and beta-carotene, NAC protected 5 people from x-ray scanner damage in one study [59].

One study determined that even high intravenous doses of NAC were safe in 28 people with kidney damage caused by chemotherapy [60].

NAC may reduce the side effects of chemotherapy and diagnostic X-rays by preventing free-radical damage.

10) Ears

According to a few studies, NAC may protect the ears from noise-induced hearing loss. NAC helped 35 people regain hearing after experiencing sudden deafness. In almost 600 soldiers who were at high risk for hearing loss, NAC slightly reduced ear damage [61, 62].

It also protected 48 textile-industry workers from hearing loss after 2 weeks [63].

But in one study of 31 people, NAC taken before listening to loud music in a nightclub had no protective effect [64].

NAC may also help with ear inflammation. It improved the symptoms in 90 children with middle ear inflammation but had a stronger effect when combined with antibiotics [65].

NAC may prevent noise-induced hearing loss and soothe ear inflammation.

11) Antibiotic Side Effects

Antibiotic side effects can arise from oxidative stress. As a strong antioxidant, NAC prevented kidney and ear damage from several strong antibiotics in two studies of 100 people [66, 67].

NAC also protected the liver from the harmful effects of anti-tuberculosis drugs in 60 patients. Those who took NAC had intact livers after treatment, while 40% of those who didn’t take NAC suffered liver damage [68].

NAC may reverse oxidative damage in the liver, kidney, and ears caused by antibiotics and anti-tuberculosis drugs.

Other Potential Benefits

The benefits below are not as well-studied or broadly recognized as those above. Keep this in mind, and remember that any single animal or cell study doesn’t mean much in the grand scheme of medical research, and the available human studies are still considered insufficient.

With that said, NAC is of particular interest to many researchers, and the results of many early studies have been promising.

1) Homocysteine and Heart Disease

B vitamins only somewhat help reduce high homocysteine. On the other hand, in one study, NAC lowered both homocysteine and high blood pressure, which helps prevent heart disease and other chronic conditions [69].

In two studies of 82 men, oral NAC lowered homocysteine and blood pressure while increasing antioxidant status over 4 weeks [69].

In another study of 60 people with heart disease, NAC lowered homocysteine levels and improved blood vessel health over 2 months [70].

NAC may cut the risk of heart disease by lowering homocysteine and high blood pressure and strengthening blood vessels.

2) Addiction

Some researchers believe that NAC has the potential to help combat various types of addiction, based on the model of binge eating in animals [71].

Cysteine from NAC may normalize brain levels of the neurotransmitter glutamate, which affects reward pathways involved in addiction [72, 73].

A large review of 165 patients and 9 studies found NAC especially useful for cannabis and cocaine addiction. NAC could also help with nicotine dependence, methamphetamine addiction, and pathological gambling [74].

It seems to help some odd types of impulsive behaviors, such as hair pulling. NAC could reduce uncontrolled hair pulling in a study of 50 people with no side effects [75].

Veterans with PTSD and addictions did a lot better after 8 weeks of NAC and psychotherapy. This approach reduced overall symptoms, craving, and depression [76].

NAC may help with drug addiction, gambling, and impulsive behavior. Some studies suggest that it balances glutamate, a neurotransmitter that controls the brain center involved in addiction.

Amphetamines

NAC helped reduce craving in 23 people with methamphetamine addiction [77].

But in another study, NAC combined with an opioid blocker (naltrexone) did not produce any benefits in 31 people with methamphetamine addiction [78].

More research is needed.

Cocaine

When it comes to cocaine dependence, some researchers believe that NAC may help reduce craving and relapse. In one study of 111 people, NAC helped maintain abstinence from cocaine over 8 weeks [79].

NAC also helped reduce cocaine desire in 15 people after just 3 days [80].

When 8 people with cocaine dependence were given NAC and taken to a brain scanner, their brain glutamate levels went down [81].

Cannabis

People addicted to cannabis who try to quit may revert to overdrinking. In 302 people addicted to cannabis, NAC could reduce alcohol consumption by 30% in those trying to quit [82].

In another study, however, NAC had no effect on cannabis addiction in adults [83].

In 116 marijuana-dependant teenagers, those taking NAC used marijuana and alcohol less frequently. Since NAC is considered very safe, it could be helpful for adolescents suffering from alcohol and cannabis overuse [84].

Several studies are still exploring the effects of NAC on cannabis addiction [85].

Nicotine

One study of almost 100 people confirmed that smokers have higher brain glutamate levels than non-smokers [86].

In 16 smokers, NAC helped maintain abstinence and reduce craving. Brain scans revealed that NAC could help restructure the brain’s reward pathways after just 4 days [87].

NAC reduced the number of cigarettes smoked in 35 people after 3 months. Almost half of the people who took NAC quit smoking, while only one-fifth of the placebo group did [88].

In another study, NAC slightly reduced nicotine withdrawal symptoms. Smokers also rated their first cigarette after NAC as less enjoyable [89].

Gambling

NAC increased the long-term benefits of psychotherapy in a 3-month study of 28 gamblers who also smoke. It could also reduce pathological gambling in 27 people after 2 months [90, 91].

NAC supplementation may help with cannabis, nicotine, and cocaine addiction by reducing cravings and withdrawal symptoms. It may also reduce pathological gambling and possibly other addictive behaviors.

3) Depression and Mood

NAC may help people with depression by [92, 93]:

  • Balancing brain glutamate levels
  • Reducing inflammation
  • Boosting the growth of new brain cells

In a review of studies including over 500 people, NAC improved symptoms of depression and overall day-to-day functioning after 3-6 months [94].

Additionally, it improved the mood of people with depression after 3-4 months [95, 93].

It may also balance mood by reducing oxidative stress in the brain. In a study of 76 depressed patients, those who took NAC had higher brain antioxidant levels [96].

NAC may improve mood in depressed patients by balancing brain glutamate and reducing oxidative stress and inflammation.

4) Bipolar Disorder and Mania

NAC could improve chronic health issues, such as heart disease and hormonal imbalance, in people with Bipolar Disorder. It had an indirect effect on overall health, antioxidant status, and inflammation [97].

In another study with 17 bipolar patients, NAC improved low mood and overall symptoms after 6 months [98].

Larger studies are currently underway to investigate the potential benefits of NAC for Bipolar Disorder [99].

NAC could also improve mania symptoms in a small study of 15 people after 6 months. The NAC group experienced less severe mania, while the placebo group experienced mood worsening [100].

People with bipolar disorder and mania may benefit from NAC supplementation, but larger clinical trials will be needed to confirm this.

5) Obsessive-Compulsive Disorder (OCD)

NAC may help with OCD by balancing glutamate and increasing antioxidants in the brain. In a study of 44 OCD patients, NAC as an add-on to standard medications improved symptoms, even in severe cases [101].

In a study of 48 OCD patients who previously didn’t respond to drugs, NAC could safely improve the symptoms after 3 months [102].

Some studies, however, didn’t find the benefits of NAC for OCD [103].

Although the evidence is mixed, NAC may be useful for obsessive-compulsive disorders, according to a large review. Overall, it shows promising benefits and has few side-effects [104].

According to limited clinical evidence, NAC may safely improve the symptoms of OCD.

6) Sleep Apnea

NAC improved sleep, reduced apnea and snoring in one study of 20 people with Obstructive Sleep Apnea after a month. Long-term, it may reduce the need for continuous positive airway pressure therapy [105].

7) Skin Health

NAC-containing creams or gels may improve skin health. NAC can boost glutathione in the skin, protecting it from damage. It can also reduce skin inflammation and normalize skin cell division. People use it for eczema, skin irritation, radiation-induced skin damage, wound healing, and acne.

In one study of 100 people, a 5% NAC gel helped reduce mild to moderate acne [106].

Case reports and animal studies support a range of skin benefits of NAC. Overall, NAC skin formulations are promising and very safe, although larger studies are harder to find [107].

Creams and gels with NAC may help with acne, eczema, and wound healing, but the available research is scarce.

8) Autism

NAC reduced irritability in a study of 33 children with autism after 3 months [108].

In two studies with 80 autistic children, those who got NAC as an add-on to an antipsychotic (risperidone) experienced less irritability and hyperactivity after two months [109, 110].

But NAC had no benefits in children with autism in a different study [111].

It could boost glutathione in 31 children with autism but had no effect on their social functioning [112].

NAC may reduce irritability and hyperactivity in children with autism, but the evidence doesn’t allow for a solid conclusion.

9) Exercise Performance

In Athletes

In one study NAC supplementation improved demanding cycling performance in 10 athletes after 9 days. It increased their antioxidant capacity, physical performance, and muscle recovery [113].

But in one study of 80 men, NAC taken before exercise didn’t increase endurance or muscle blood flow [114].

One study concluded that NAC can alter the energy balance in muscles and hinder muscle repair. When given to 10 men after intense exercise, it lowered inflammation in the muscles but at the same time slowed down muscle recovery after 8 days [115].

And in another, NAC worsened performance and decreased power output during HIIT training in 9 athletes [116].

In a study of 12 men, NAC improved exercise performance after 6 days [117].

Muscle Fatigue & Inflammation

In several studies of 16 people in total, NAC infusions given before intense exercise reduced post-exercise muscle fatigue [118, 119].

NAC could help maintain high levels of the anti-inflammatory IL-10 even a week after exercising in 29 people [120].

Power Training

NAC could reduce muscle fatigue in exercises that demanded only 80% muscle power, while it wasn’t beneficial for high-power training in 7 men [121].

NAC increased glutathione and blood cysteine in several studies in healthy people, which was linked to improved strength, endurance, and exercise performance [122, 123].

Inactive or Elderly People

NAC taken for a week before exercising could speed up muscle repair and increase blood flow to the muscles in a study of 29 sedentary men [124].

NAC also increased muscle strength in older people whose antioxidant levels are low. It also reduced TNF-alpha, an inflammatory marker [125].

NAC may improve blood flow and muscle inflammation during short-term intense exercise, but it may prevent muscle recovery after exercise in the long run.

10) Anemia

In 61 people with thalassemia, an “antioxidant cocktail”, containing NAC with curcuminoids or vitamin E, improved anemia and hemoglobin levels after 4 months. NAC had similar benefits in 75 children with thalassemia, while also reducing DNA damage [126].

It also improved blood markers and antioxidant levels in 11 people with sickle cell anemia [127].

NAC combined with oxygen increased erythropoietin production in 38 healthy people, which would also be beneficial for those with anemia [128].

NAC may boost hemoglobin and red blood cell production in people with different types of anemia.

11) Pain and Inflammation

NAC may be anti-inflammatory. In cells, it could target the same pathway as common anti-inflammatory painkillers: COX-2 [6].

NAC could alleviate pain in a study of 146 people over 2 years, especially in those with poor circulation. The participants took 1,200 mg NAC daily [129].

NAC (1,200 mg/day) reduced inflammatory markers such as CRP and IL-6 in a study of 24 people with kidney disease. Given to 15 patients with severe burns, NAC reduced oxidative damage, increased antioxidant protection, and reduced inflammatory markers [130, 131].

But it had no effect on kidney inflammation in kids nor on leg cramps [132, 133].

NAC reduced neuropathic pain in rats by blocking an important inflammatory pathway: matrix metalloproteinases [134].

NAC may reduce pain and inflammation of different origins, including kidney disease, injuries, and severe burns

12) Insulin Resistance and Type 2 Diabetes

NAC can reduce insulin resistance thanks to its antioxidant effects. Plus, people with type 2 diabetes may have lower glutathione levels that NAC can replenish [135].

In one study of 14 diabetic patients, NAC (1,200 mg daily for one week) increased glutathione in platelets and normalized their activity, which could protect from heart disease in type 2 diabetes [136].

When given to 128 people before a high-fat meal, NAC could help maintain antioxidants and blood vessel health. It reversed oxidative stress, which was very noticeable in people with type 2 diabetes and insulin resistance. NAC may thus delay or prevent the use of anti-diabetes drugs in type 2 diabetes [137].

Animal studies speak to its benefits, too. NAC prevented mice fed a high-fat diet from gaining excessive weight and symptoms of insulin resistance [138].

NAC can provide antioxidant support and improve blood sugar control in patients with type 2 diabetes and insulin resistance.

13) Alzheimer’s Disease

An antioxidant supplement containing NAC improved cognition and mood in 130 people with Alzheimer’s disease. Participants took the supplement for up to one year [139].

In one trial, NAC alone also improved symptoms of Alzheimer’s Disease after 3-6 months [140].

In mice with Alzheimer’s Disease, NAC prevented brain damage, memory, and cognitive decline. It could restore normal acetylcholine signaling and energy use in the brain [141].

Alone or in combination with other antioxidants, NAC may reduce the symptoms and boost cognition in patients with Alzheimer’s disease.

14) Parkinson’s Disease

NAC may protect the brain in people with Parkinson’s Disease. In one clinical study, it improved the activity of dopamine neurons, which are incredibly important in this disease [142].

NAC also increased glutathione levels in the brains of 3 people with Parkinson’s Disease [143].

15) Schizophrenia

NAC may help improve symptoms of schizophrenia and psychosis by balancing the brain’s glutamate levels and fighting oxidative stress and inflammation.

NAC improved cognition and working memory in 58 people with psychosis, taken at a higher dose of 2 g/day. It also reduced symptoms like mania and hallucinations and improved response to standard treatment in another study of 121 people [144].

Combined with antipsychotics, NAC improved overall symptoms in 42 people with schizophrenia with no side effects. It especially helped with low mood and apathy [145].

NAC may reduce manic and psychotic symptoms in patients with schizophrenia and improve their cognition.

16) Heart Disease

In almost 100 patients who had heart attacks, NAC accelerated short-term recovery. In the longer term, some researchers believe it may improve heart health and reduce complications  [146].

Oxidative damage is one of the underlying causes of heart disease. NAC prevented heart damage in mice with diabetes [147].

It also reduced heart damage in rats with chronic heart failure, while also improving fatigue and exercise tolerance [148].

Serious heart arrhythmias are also linked to oxidative stress. In blood taken from patients, those who took NAC had higher antioxidants and reduced inflammation [149].

By scavenging free radicals, NAC may repair heart damage and cut the risk of heart disease, but the clinical evidence is weak.

17) Bone Health

In 21 women who recently went through menopause, NAC strengthened the bones when added to a vitamin D and calcium supplements. They used it safely for over 3 months [150].

In rats, NAC enhanced bone growth, mineralization, and regeneration while also boosting collagen [151, 152].

18) Ulcers and H. Pylori

H.pylori is the most common cause of ulcers. NAC enhanced the effects of H.Pylori treatment in one study of under 100 people. In another one (60 patients), it helped antibiotics penetrate to the site of infection [153, 154].

NAC may play a role in overcoming antibiotic resistance by destroying biofilms. NAC increased the sensitivity of H.Pylori to antibiotics by disrupting biofilms in a study of 40 people. It could be given before antibiotics to boost their effect [155].

NAC may boost the effects of antibiotics on H. Pylori infection and thus help treat stomach ulcers.

19) ALS

Oxidative stress plays a role in diseases like ALS, and NAC offers some hope for ALS patients. But so far, it only prevented ALS-like degeneration of brain cells [156].

20) Gut Health and SIBO

As a powerful antioxidant, NAC can help protect the gut and reduce small intestinal bacterial overgrowth (SIBO).

Gastric reflux, or heartburn, is alarmingly common. In 90 people with gastric reflux (GERD), NAC improved most symptoms after 3 months when added to standard PPI drugs [157].

PPIs can often cause SIBO as they increase the gut pH, making it more hospitable for bacteria. Several strains of antibiotics combined with NAC can reverse the condition. Once reversed, NAC and probiotics restored the gut barrier and prevented SIBO in the long run [158].

NAC also reduced gut inflammation In 37 people with colitis, helping to reduce inflammatory substances like IL-8 [159].

In rats, it could also reduce leaky gut, helping to strengthen the intestinal barrier and boost antioxidant defense [160].

NAC may help relieve heartburn and stop bacterial overgrowth caused by acid reflux drugs. It balances the gut microbiome, reduces inflammation, and strengthens the gut lining.

21) Cognition

Combinations of NAC with other antioxidants improved cognition in healthy older people and those with mild cognitive impairment [161, 162].

Scientists have been researching NAC for boosting cognitive function in Alzheimer’s, Parkinson’s, schizophrenia, and anesthesia recovery [163].

22) Brain and Spine Injuries

NAC could reduce the effects of traumatic brain injuries during combat, according to a study of 81 US soldiers [164].

It can cross the blood-brain barrier in children with traumatic brain injuries without side effects [165].

In pregnant women with vaginal infections, NAC could protect their fetuses from harmful effects on the brain [166].

In rats, NAC could protect from spinal and brain trauma and restore energy balance in the cells [167, 168].

NAC may aid in brain or spinal trauma recovery and reduce the free-radical damage from various stressors.

23) Kidney Disease

Oxidative stress can cause kidney failure in severe cases, and NAC was able to prevent this in rats [169].

At least 30 clinical studies have looked at the protective effects of NAC in kidney injury, before or after kidney surgery, and thyroid problems in kidney disease.

Most of the studies have shown positive results, which brings NAC into sharp relief as a potential treatment for severe cases of kidney disease [170, 171, 172, 7, 173, 174, 175].

When used in serious diseases and to reduce organ damage, NAC is usually given as an infusion or injection.

Injected NAC may prevent kidney failure in cases of surgery, trauma, and thyroid disorders.

24) Lupus and ADHD

People with lupus have dysfunctional T cells, an important component of the immune system. T cells can be rebalanced by increasing glutathione with NAC. In one trial, NAC (2.4-4.8 g/day) improved lupus and blocked mTOR in 36 people after 3 months [176].

Lupus also increases the likelihood of suffering from ADHD. NAC reduced ADHD symptoms in patients with lupus in a study of almost 100 people. NAC (up to 5 g/day) improved cognition, impulsivity, and overall symptoms [177].

NAC may balance the immune system in patients with lupus, improve their symptoms, and lower their risk of suffering from ADHD.

25) Cancer

NAC showed anti-cancer activity in cellular and tissue studies [178, 179, 180].

It also prevented oxidative DNA damage from radiation in animals [181].

In one study of 25 women who had cancer and were in remission, NAC helped rebalance hormone levels [182].

Animal and cell studies indicate the anti-cancer potential of NAC, but no clinical trials have confirmed this yet.

26) HIV

People with HIV have lower antioxidant and glutathione levels. NAC boosted glutathione in 12 people with HIV after only a week. In another 6-month study, 600 mg NAC daily reduced the HIV virus number and activity while boosting the immune response [183, 184, 185].

NAC could boost the activity of macrophages and glutathione levels in people with HIV and tuberculosis, which helps fight off the infections [186].

Higher glutathione levels from NAC could prevent the HIV virus from replicating in cells [187].

By boosting glutathione and fighting oxidative stress, NAC may strengthen the immune response to infections such as HIV and tuberculosis.

27) Gum Health

In a study of 33 people, NAC reduced gum bleeding after surgery [188].

28) Mountain Sickness

NAC helped with mountain sickness in one study in 84 people living in very high altitudes in Peru (over 4,000m). It did not work better than the standard drug, acetazolamide, however [189].

29) Cystic Fibrosis

NAC reduced inflammation and increased antioxidants in 18 glutathione-deficient women with cystic fibrosis [190].

The short-term effects are not that evident, but long-term NAC use may be more beneficial [191].

30) In Pregnancy

There is not enough research to claim whether NAC is safe in pregnancy, so we advise against taking it if you are pregnant. If you want to incorporate NAC into your health strategies while you are pregnant, make sure you talk to your doctor first.

A combination of NAC and folic acid helped prevent unexplained pregnancy loss in 80 women. In 29 pregnant women low antioxidant status, NAC in combination with other antioxidants improved pregnancy outcomes [192, 193].

NAC could protect the fetus from a brain injury caused by the mother’s bacterial infection. It also helped prevent preterm births in 280 women with vaginal infections [194, 166].

Antioxidant effects of NAC may protect the fetus from the mother’s vaginal infections and improve pregnancy outcomes. Pregnant women shouldn’t take NAC before consulting their doctor.

31) Compulsions in Children

NAC safely reduced obsessive skin picking in a study of 66 children with the disorder [195].

It could also reduce compulsive nail biting in 42 children [196].

It seems to help only with obsessive or compulsive behaviors as it did not improve tic symptoms in 31 children with Tourette Syndrome [197].

NAC may help with compulsive behaviors in children such as skin picking and nail biting.

32) Dry Eyes

Just one application of NAC eye drops helped improve dry eye symptoms in a study of 38 people. The eye drops contained NAC bound to chitosan (chitosan-NAC) [198].

A 5% NAC cream worked as well as the typical steroid cream in 20 people with dry eye syndrome. It improved burning, itching, and blurry vision after a month. It was also much more effective than artificial tears in another study of 20 people with dry eyes [199, 200].

Creams and eye drops with NAC may reduce itching and other symptoms of dry eyes.

NAC Side Effects & Precautions

Side Effects

NAC seems to be a safe substance with few known side effects. Occasionally, oral supplements can cause digestive issues such as [201, 32, 74]:

  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation

NAC blocks an enzyme called DAO (by about 20%). Since DAO breaks down histamine, it is possible that NAC may trigger a histamine reaction in some people. Low DAO can cause food sensitivities, skin reactions, flushing, asthma, gastrointestinal problems, and other symptoms [202, 203, 204].

Because of the sulfur-containing cysteine, NAC does smell bad (sulfur smells like rotten eggs), which makes the powder form unappealing for most people.

NAC is safe and well-tolerated in most people. It may cause digestive issues and, in rare cases, histamine reaction that resembles allergies or food sensitivity.

Sensitive Groups

People with severe liver damage can’t make glutathione (GSH) from cysteine and may need to take GSH itself [20].

Since NAC can impact the platelets and reduce coagulation, consult your doctor if you [73]:

  • Have a bleeding disorder
  • Are having surgery soon
  • Take blood-thinning medications

In rats, high doses of NAC (12 mg/kg/day) impaired the blood vessels in the brain. Clinical trials haven’t confirmed this effect [205, 206].

Children and pregnant women should avoid NAC unless prescribed by their doctor.

Avoid NAC if you have a bleeding disorder, take blood thinners, or anticipate surgery. Pregnant women should consult their doctor before taking NAC.

NAC Sources

Supplement Dosage

Remember that NAC is not approved by the FDA for any purpose except to treat acetaminophen toxicity. That means that there is no official safe dose of NAC.

1800 – 2,400mg of NAC was very common across clinical studies, typically divided into 2-3 doses throughout the day.

Some studies for fighting addiction and mental health issues used doses closer to 3,000 mg/day.

For general wellness or gut health, 600 mg a day is the typical dose.

A maximum safe dose of NAC has yet to be determined.

Clinical trials safely used 800-2,400 mg of NAC daily, divided into 2-3 doses. The typical dosage for milder acute conditions is 600 mg a day. However, there is no approved safe dose of NAC.

Is It In Food?

The simple answer is no.

NAC is not found in foods. However, you can get cysteine—the amino acid NAC releases—from various foods.

L-cysteine in Food

As an amino acid, cysteine is found in protein-rich foods. The other sulfur-containing amino acid is methionine, which also helps make glutathione [207].

Food sources of cysteine (which also provide methionine) include [207]:

  • Red meat and poultry (equal cysteine/methionine ratio)
  • Eggs (higher in cysteine)
  • Fish (higher in methionine)
  • Dairy (higher in methionine)
  • Grains and starch-rich foods (higher in cysteine than in methionine)
  • Soybeans (lower in both amino acids than animal proteins)

Additionally, your body can make cysteine from other sulfur-containing compounds found in foods, such as [207]:

  • Garlic
  • Onions
  • Broccoli and other cruciferous vegetables

Your body uses sulfur for sulfation, a crucial detox pathway, and to make other important compounds like SAM. You detox drugs such as acetaminophen (Tylenol) via sulfation, and they deplete your glutathione reserves [207].

This means that reducing your intake of acetaminophen-containing OTC painkillers like Tylenol can lower the strain on your liver, lower your dietary sulfur requirements, and allow your body to make better use of sulfur compounds.

You can’t get NAC from food, but you can boost glutathione by consuming sulfur-containing amino acids and nutrients from animal foods, beans, whole grains, and some vegetables.

Takeaway

N-acetyl cysteine (NAC) is an amino acid with powerful antioxidant properties. It helps build the master antioxidant, glutathione. Thanks to this effect, NAC can protect the liver, heart, and lungs against injury, drugs, toxins, and other stressors.

NAC supplementation can boost the immune system, combat addictions and mental disorders, boost fertility, and help with anemia. According to limited evidence, it may also help with pain, insulin resistance, brain damage, gut disorders, and kidney disease.

The daily dosage ranges from 800-2,400 mg, divided into 2-3 doses; milder conditions require 600 mg of NAC per day. You can boost glutathione naturally by getting cysteine and sulfur compounds from protein-rich foods, garlic, onions, and cruciferous vegetables.

NAC is safe in most cases, but it tastes bad and may upset the stomach. Avoid it if you have a bleeding disorder, upcoming surgery, or take blood thinners. Pregnant women should consult with their doctor before taking NAC.

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About the Author

Ana Aleksic

MSc (Pharmacy)
Ana received her MS in Pharmacy from the University of Belgrade.
Ana has many years of experience in clinical research and health advising. She loves communicating science and empowering people to achieve their optimal health. Ana spent years working with patients who suffer from various mental health issues and chronic health problems. She is a strong advocate of integrating scientific knowledge and holistic medicine.

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