NAC (N-Acetyl Cysteine) is an antioxidant with numerous potential health benefits. It may help with mood disorders, sleep, infections, and inflammation. It boosts 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 N-acetyl cysteine (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.
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 prevent the flu
- Biofilm disruptor
- Potential to improve fertility
- May help with many chronic health problems
Skeptics:
- 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.
Effective For
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 [3].
It could help with heart attack complications, assisted breathing, abdominal surgery, and pancreatitis when used in the emergency case, before or after surgery [4, 5, 6, 7].
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 [8, 9].
NAC can safely prevent serious liver damage from acetaminophen and increase survival, according to several studies of over 400 patients [8, 10].
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 [11].
NAC has been studied a lot in intensive care units, as a possible way to reduce organ damage before and after surgery [3].
Possibly Effective For
2) Detox
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 [12, 13].
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 [14].
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 [15, 16].
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 [17].
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 [18].
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 [19].
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 [20].
Chemical Warfare
NAC improved breathing, cough, congestion, and lung function in 144 people with poisoning from a chemical warfare agent (mustard gas) [21].
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 [22].
Chemotherapy and X-Rays
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 [23].
NAC infusions also reduced mouth ulcers and inflammation from chemotherapy in 80 people with leukemia [24].
Oral NAC protected from the side effects of chemotherapy on the brain in 14 people with colon cancer [25].
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 [26].
One study determined that even high intravenous doses of NAC were safe in 28 people with kidney damage caused by chemotherapy [27].
3) 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 [28].
According to a large review, NAC improved symptoms and prevented disease worsening in people with chronic bronchitis with no side effects. It needed to be taken for at least 3 – 6 months, as 2 months of NAC did not improve COPD in one study [28, 29].
Combined with vitamin C, NAC increased the antioxidant and nutritional status in 79 people with COPD [30].
High doses over 1 year were safe and improved lung capacity and breathing in people with COPD in another study [31].
NAC has also been given alongside oxygen, the typical COPD treatment. In 45 patients, it could prevent oxidative damage that can result from long-term oxygen treatment [32].
Lung Damage and Infections
NAC does not appear to 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 [33, 34].
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 [35].
Inhaled NAC also helped with airway infections in a study of 100 small children [36].
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of NAC for any of the below-listed uses. Remember to speak with a doctor before taking NAC, and never use it in place of something your doctor recommends or prescribes.
4) Liver Health
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 86% of all cases, according to a study of 69 patients. It could protect the liver from factors such as excessive alcohol and environmental pollutants [37].
NAC injections helped increase liver function better than glutathione in one study of 75 patients with Hepatitis B [38].
5) Oxidative Stress
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% [39, 40].
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 [41].
NAC also increased red blood cells and markers of their function and size (erythropoietin, hemoglobin, hematocrit, MCV) [39, 40].
NAC vs. Glutathione
Oral glutathione has poor bioavailability, and taking NAC is considered one potential way to circumvent this problem. 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 [42].
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 [42].
6) Flu
Since NAC decreases the body’s inflammatory response, some researchers believe that 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 [43].
NAC is also sometimes added as a complement to standard treatments of sinus inflammation and infections [44, 45].
In cells, NAC reduced replication of the flu virus. If the virus can’t replicate quickly, it’s easier to fight it off [46].
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 or complementary approach, but the studies so far have mixed results [47].
In the largest study of NAC in 150 women with PCOS who previously didn’t respond to treatments, NAC added to clomiphene citrate improved ovulation and pregnancy rates after just 5 days. Another study of over 100 women confirmed this [48, 49].
In 60 women with PCOS, NAC improved the quality of egg cells. It also increased embryo health during in vitro fertilization [50].
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 [51]:
- 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 [52].
NAC improved insulin sensitivity in another study of 31 women with PCOS over 5 – 6 weeks [53].
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 [47].
8) Male Fertility
Aside from helping women with PCOS, antioxidant therapies like NAC may increase fertility in men [54].
Oxidative stress can damage the sperm’s DNA, which reduces fertility [55].
In 120 infertile men, NAC improved semen quality and antioxidant status after 3 months [56].
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 [57].
In a large study of almost 500 infertile men, NAC with selenium improved semen quality after 6 months [58].
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 [55].
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.
9) Hearing Loss
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 [59, 60].
It also protected 48 textile-industry workers from hearing loss after 2 weeks [61].
But in one study of 31 people, NAC taken before listening to loud music in a nightclub had no protective effect [62].
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 [63].
10) 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 [64, 65].
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 [66].
11) Homocysteine and Heart Disease
B vitamins 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 [67].
In two studies of 82 men, oral NAC lowered homocysteine and blood pressure while increasing antioxidant status over 4 weeks [67].
In another study of 60 people with heart disease, NAC lowered homocysteine levels and improved blood vessel health over 2 months [68].
12) 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 [69].
13) 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 [70].
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 [71].
14) 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 [72].
But in one study of 80 men, NAC taken before exercise didn’t increase endurance or muscle blood flow [73].
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 [74].
And in another, NAC worsened performance and decreased power output during HIIT training in 9 athletes [75].
In a study of 12 men, NAC improved exercise performance after 6 days [76].
Muscle Fatigue & Inflammation
In several studies of 16 people in total, NAC infusions given before intense exercise reduced post-exercise muscle fatigue [77, 78].
NAC could help maintain high levels of the anti-inflammatory IL-10 even a week after exercising in 29 people [79].
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 [80].
NAC increased glutathione and blood cysteine in several studies in healthy people, which was linked to improved strength, endurance, and exercise performance [81, 82].
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 [83].
NAC also increased muscle strength in older people whose antioxidant levels are low. It also reduced TNF-alpha, an inflammatory marker [84].
15) 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 [85].
It also improved blood markers and antioxidant levels in 11 people with sickle cell anemia [86].
NAC combined with oxygen increased erythropoietin production in 38 healthy people, which would also be beneficial for those with anemia [87].
16) Pain and Inflammation
NAC alleviated pain in a study of 146 people over 2 years, especially in those with poor circulation. The participants took 1,200 mg NAC daily [88].
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 [89, 90].
But it had no effect on kidney inflammation in kids nor on leg cramps [91, 92].
NAC reduced neuropathic pain in rats by blocking an important inflammatory pathway: matrix metalloproteinases [93].
In cells, NAC targeted the same pathway as common anti-inflammatory painkillers: COX-2 [94].
17) Diabetes
NAC may reduce insulin resistance thanks to its antioxidant effects. Plus, people with type 2 diabetes may have lower glutathione levels that NAC can replenish [95].
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 [96].
When given to 128 people before a high-fat meal, NAC helped maintain antioxidants and blood vessel health. It reduced oxidative stress, which was very noticeable in people with type 2 diabetes and insulin resistance [97].
Animal studies speak to its benefits, too. NAC prevented mice fed a high-fat diet from gaining excessive weight and symptoms of insulin resistance [98].
18) Parkinson’s Disease
Some research has suggested that 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 [99].
NAC also increased glutathione levels in the brains of 3 people with Parkinson’s Disease [100].
19) Heart Health
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 [101].
Oxidative damage is one of the underlying causes of heart disease. NAC prevented heart damage in mice with diabetes [102].
It also reduced heart damage in rats with chronic heart failure, while also improving fatigue and exercise tolerance [103].
Serious heart arrhythmias are also linked to oxidative stress. In blood taken from patients, those who took NAC had higher antioxidants and reduced inflammation [104].
20) 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 [105].
In rats, NAC enhanced bone growth, mineralization, and regeneration while also boosting collagen [106, 107].
21) Ulcers and H. pylori
- 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 [108, 109].
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 [110].
22) 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 [111].
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 [112].
NAC also reduced gut inflammation In 37 people with colitis, helping to reduce inflammatory substances like IL-8 [113].
In rats, it could also reduce leaky gut, helping to strengthen the intestinal barrier and boost antioxidant defense [114].
23) Brain and Spine Injuries
NAC could reduce the effects of traumatic brain injuries during combat, according to a study of 81 US soldiers [115].
It can cross the blood-brain barrier in children with traumatic brain injuries without side effects [116].
In pregnant women with vaginal infections, NAC could protect their fetuses from harmful effects on the brain [117].
In rats, NAC could protect from spinal and brain trauma and restore energy balance in the cells [118, 119].
24) Kidney Injury & Failure
Oxidative stress can cause kidney failure in severe cases, and NAC was able to prevent this in rats [120].
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 [121, 122, 123, 3, 124, 125, 126].
When used in serious diseases and to reduce organ damage, NAC is usually given as an infusion or injection.
25) Gum Health
In a study of 33 people, NAC reduced gum bleeding after surgery [127].
26) 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 [128].
27) Cystic Fibrosis
NAC reduced inflammation and increased antioxidants in 18 glutathione-deficient women with cystic fibrosis [129].
The short-term effects are not that evident, but long-term NAC use may be more beneficial [130].
28) 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 [131, 132].
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 [133, 117].
29) 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) [134].
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 [135, 136].
Animal & Cell Research (Lacking Evidence)
No clinical evidence supports the use of NAC for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
30) 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 [137].
Cancer Research
NAC showed anti-cancer activity in cellular and tissue studies [138, 139, 140].
It also prevented oxidative DNA damage from radiation in animals [141].
In one study of 25 women who had cancer and were in remission, NAC helped rebalance hormone levels [142].
Further Reading
- What is NAC? Side Effects, Dosage, Mechanism, Reviews
- NAC for Mental Health, OCD, Anxiety & Depression
- Can NAC Help Fight Coronavirus?
Takeaway
N-acetyl cysteine (NAC) is a common supplemental form of the amino acid cysteine. The human body uses it to produce antioxidants, and emergency responders and doctors use it to prevent acetaminophen poisoning.
NAC is believed to help with other types of detoxification as well, from heavy metals to pesticides to chemotherapy side effects. Other research suggests that it may help with lung diseases and damage from COPD and infection.
Researchers are currently investigating whether NAC could be helpful in many other contexts. Limited clinical evidence suggests a potential role in liver health, immune function, PCOS, fertility, heart disease, exercise performance, diabetes, and more.
