N-acetyl cysteine (NAC) is a synthetic form of cysteine, a semi-essential amino acid. When consumed, NAC breaks down into cysteine, which is metabolized to glutathione. Glutathione is a vital antioxidant for proper immune system functioning and detoxification, as well as tissue building and repair.
There are several health claims around the NAC supplement, with benefits ranging from improved mental health, protection against certain viruses and relief from respiratory symptoms—but many of these claims haven’t been approved by the Food and Drug Administration (FDA).
Read on to learn more about NAC, including potential health benefits, which uses are FDA-approved and possible side effects.
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Health Benefits of NAC (N-Acetyl Cysteine)
“Many acute and chronic health conditions, including aging [related issues], diabetes and heart disease are associated with low glutathione levels. Because of this, glutathione supplementation is often recommended to prevent or treat diseases,” explains Kelly Johnson-Arbor, M.D., medical toxicologist and co-medical director at the National Capital Poison Center in Washington, DC. “Since oral glutathione is not absorbed well by the human body, its precursor—NAC—is often used to achieve higher glutathione levels.”
While NAC is believed to be associated with a range of health benefits, many of these claims lack sufficient evidence from human-based research. The supplement has, however, gained FDA approval for the treatment of acetaminophen (Tylenol) poisoning.
FDA Approved for Acetaminophen Poisoning
NAC is a commonly used—and FDA-approved— drug for treating acetaminophen poisoning. Taken in large doses, acetaminophen can cause damage to the liver. When administered through oral or intravenous routes, NAC may reduce the extent of this damage—although it cannot reverse damage that has already been done.
NAC is believed to work by increasing glutathione levels, which function as a powerful detoxifier in the liver. The glutathione then helps inactivate N-acetyl-p-benzoquinone imine (NAPQI), a toxic byproduct of acetaminophen. However, prompt administration is crucial. Research shows NAC is most effective when given within eight hours of ingesting acetaminophen.
May Help Relieve Respiratory Disease Symptoms
Evidence suggests NAC may be an effective treatment for certain respiratory conditions, such as chronic bronchitis or chronic obstructive pulmonary disease (COPD).
Many of these airway conditions are characterized by excess mucus production and inflammation. Although the body produces mucus to protect itself from contaminants in the air, too much of it can impede proper breathing and decrease lung function.
NAC is thought to help break apart and thin mucus secretions in the airways, making it easier to expel and clear the airway through coughing.
May Help Improve Certain Mental Health Conditions
There’s preliminary evidence that NAC may help improve certain mental health conditions.
For example, a small 2018 study found that NAC improved symptoms of schizophrenia when used in addition to antipsychotic medication. The supplement was associated with an improvement in negative symptoms, including emotional expression , thought and speech productivity and motivation, as well as a better attention span[1]Tharoor H, Mara S, Gopal, S. Role of Novel Dietary Supplement N-acetyl Cysteine in Treating Negative Symptoms in Schizophrenia: A 6-Month Follow-up Study. Indian Journal of Psychological Medicine. 2018;40(2):139–142. .
Evidence also supports NAC for treating other mental health conditions, such as substance use disorders, obsessive compulsive disorder (OCD) and mood disorders. However, more research is needed to determine the effectiveness of NAC in these conditions.
May Improve Brain Health
Some research suggests NAC may improve brain health and help reduce symptoms associated with some neurodegenerative diseases, including Alzheimer’s and Parkinson’s disease. It may also help relieve neuropathic pain caused by central nervous system damage.
More research is needed to confirm the effects of NAC on brain health. Still, the supplement’s ability to increase glutathione levels and help protect against oxidative stress—a disturbance in the balance between the production of free radicals and antioxidant defenses that can cause cell damage—may contribute to its neuroprotective effects.
May Help Treat Certain Viral Infections
“NAC’s potential activity against SARS-CoV-2 is still under clinical studies. However, there are clinical studies to support its use to decrease the severity, duration and frequency of influenza, common colds, recurrent bronchitis and recurrent pneumonia,” says Jia-Yia Liu, M.D., an infectious disease specialist and creator of NACPRO+, a supplement primarily based on the properties of NAC.
Research suggests NAC works against viral infections by boosting the immune system, reducing inflammation and preventing the replication of viruses. While continued research is needed to confirm these effects, NAC supplements may offer some benefits for people struggling with viral infections.
May Improve Male Infertility
Some studies suggest NAC may help improve sperm quality and reduce oxidative stress in infertile men.
A small 2019 study found that men who took NAC orally for three months experienced significantly higher sperm count and motility (the ability for sperm to move effectively)[2]Jannatifar R, Parivar K, Roodbari NH, et al. Effects of N-acetyl-cysteine supplementation on sperm quality, chromatin integrity and level of oxidative stress in infertile men. Reproductive Biology and Endocrinology. 2019;17:24. . The findings also suggest that NAC may help improve abnormal sperm structure and reduce DNA damage to the sperm.
Based on this data, it’s believed supplementation of NAC may positively impact overall sperm quality and, therefore, may help improve male infertility.
May Improve Chronic Kidney Disease
Chronic kidney disease (CKD) is a condition that occurs when your kidneys are damaged and can’t function properly. As a result, the body can’t get rid of waste and excess fluid, leading to other health concerns—including high blood pressure and heart disease.
Some research suggests supplementation of NAC may have the potential to help slow the progression of CKD. However, other studies contradict these findings. Further research is needed to determine the effectiveness of NAC in CKD
Possible Side Effects of NAC
While NAC is generally considered safe, side effects can occur.
Possible side effects of NAC include:
- Gastrointestinal (GI) symptoms, such as nausea, vomiting or diarrhea
- Low blood pressure
- Anaphylactic reactions, such as rash, swelling, tightness of the chest or difficulty breathing
- Increased heart rate
- Dizziness or lightheadedness
In most cases, adverse side effects of NAC are mild. However, the supplement isn’t right for everyone. People with certain medical conditions should avoid taking NAC.
Don’t take NAC if you have a bleeding disorder, know you are allergic to NAC or suffer from cystinuria (a rare kidney stone condition). NAC can also potentially elevate your hom*ocysteine levels in high doses, which is an amino acid associated with heart disease, explains Dr. Liu.
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Although NAC is available with and without a prescription, our experts agree that anyone considering a NAC supplement should first talk with their doctor.
“Tell your doctor about all medications you are taking, including prescription drugs and over-the-counter products, including dietary supplements. Your doctor can carefully check your list of medications to ensure that you aren’t at risk for experiencing drug to drug interactions and evaluate your medication regimen for potential side effects,” says Dr. Johnson-Arbor.
Additionally, because the FDA does not regulate supplements for safety or effectiveness, it’s important to do your research and choose a brand that includes quality ingredients. One way to do this is to opt for a brand that has been verified via the independent, nonprofit US Pharmacopoeial (USP) Convention Dietary Supplement Verification Program, indicating that the supplement you have chosen has been third-party tested for quality.
Overall, NAC may provide a range of health benefits—but it’s important to speak with your doctor before adding NAC to your routine to ensure the potential benefits outweigh the risks.
