In health circles, NAC is the internationally recognized abbreviation for N-Acetylcysteine, which is quite a mouthful to say, read, or write. NAC is an important and low-cost supplement that has been used in medicine for years, when treating a wide range of acute and chronic conditions. Although well known for the treatment of excessive mucus production in respiratory conditions and to treat toxicity due to a paracetamol overdose, ongoing research shows promising results for NAC to aid treatment in a wide range of medical conditions.
Dietary protein is broken down during digestion into amino acids, which are small molecules that combine to make the various proteins that the cells in the body need. Twenty different naturally occurring amino acids are required by the body for these processes, consisting of non-essential amino acids which the body produces, and essential amino acids that must come from food. NAC is a synthetic form of cysteine, one of the non-essential amino acids produced in the body.
How NAC works:
NAC is a medication and dietary supplement well known for its remarkable antioxidant and anti-inflammatory boosting properties. Antioxidants are compounds that help to fight diseases in the body, while anti-inflammatories help to reduce swelling and irritation in the body’s tissue caused by inflammation.
In the body, NAC converts to cysteine, a precursor for the production of glutathione, which is made from three amino acids (a tripeptide), namely glycine, cysteine, and glutamic acid. While there is usually ample glutamic acid in the body, glycine and cysteine are the two rate limiting amino acids in glutathione production, which can be boosted by supplementation. NAC is used in supplements rather than l-cysteine, as NAC may be less toxic in large doses, and more soluble than L-cysteine by itself.
Glutathione is found in all cells of the body and is a vital antioxidant for proper immune functioning and detoxification, as well as tissue building and repair. Glutathione also addresses mitochondrial dysfunction, and the oxidative stress (an imbalance between free radicals and antioxidants) caused by free radicals. Free radicals are unstable atoms that can cause inflammation and cell damage.
Normal aging and age-related disorders lead to mitochondrial dysfunction, when energy producing mitochondria in cells don’t work as well as they should, and an increase in free radicals, both of which accelerate aging and contribute to the onset of age-related diseases such as chronic inflammation, type 2 diabetes, metabolic disorder, cardiovascular diseases, dementia, and others. Mitochondrial dysfunction underlines the need for increased levels of glutathione.
Potential NAC health benefits:
There are several health claims around NAC supplements. It is a proven treatment for paracetamol overdose and to break up mucus in the lungs and airways. Preliminary results from studies have indicated that NAC supplementation may contribute to improvement in a wide range of health conditions.
As glutathione taken in oral form is not well absorbed by the body, NAC as its precursor is often used as supplement to achieve higher levels of glutathione. As such, NAC is associated with a wide range of health benefits, although in some cases there is a lack of sufficient evidence from human-based research.
Discussed clockwise according to the image above, there are promising evidence from current studies that NAC may help to improve these health conditions:
- Liver diseases & paracetamol overdose: Oxidative stress is a crucial factor in the progression of acute and chronic liver diseases. Studies have evaluated the efficacy of NAC in modulating inflammation and oxidative stress in liver diseases. For example, NAC is proven as a safe and effective drug to treat paracetamol poisoning and its toxic effects on the liver, as boosting the levels of glutathione speeds up the breakdown of paracetamol. As glutathione levels are depleted in liver disease, the function of NAC is to help replenish the stocks of glutathione.
- Neurogenerative diseases: As NAC can effectively cross the blood-brain barrier, it helps to raise glutathione levels in the brain, exhibiting anti-inflammatory actions. NAC also aids in controlling the neurotransmitter glutamate. Studies are ongoing to determine the effect that supplementation with NAC may have in improving the symptoms of Parkinsons, Alzheimer’s, and multiple sclerosis, which are all linked to inflammatory conditions in the brain.
- Sickle cell disease: NAC has been proposed for the treatment of patients with sickle cell anemia, an inherited blood disorder that effects the oxygen carrying hemoglobin in the blood stream, as this disease is associated with an increase in oxidative stress and the accompanying reduction in antioxidant activity.
- Cardiovascular diseases: As oxidative stress plays a role in the development and progression of cardiovascular disease; NAC has been linked to improved cardiac function. Some clinical and experimental studies have shown the protective role that NAC may play in conditions such as heart failure, coronary artery disease, and acute myocardial infarction.
- Substance use disorders: Studies have shown that NAC may be a promising agent for the treatment of substance abuse disorders by helping to ease the symptoms of withdrawal, including the strong craving for drugs, which may also help to lessen relapses.
- Psychiatric illnesses: Supplementation with NAC has shown moderate benefits in treatment with antipsychotic medication. One of the mechanisms by which NAC may help to modulate the symptoms of psychiatric disorders is suspected to be its impact on the reduction of inflammatory cytokines. (Cytokines are molecules that allow cells to talk to each other and are crucial for a healthy immune system.) Increased oxidative stress and deficits in the glutathione system are for example linked to schizophrenia, while inflammatory and oxidative processes that contribute to neuroinflammation seem to be part of major depression disorders. However, information on the use of NAC as an adjunct therapeutic strategy in most psychiatric disorders is still limited.
- Kidney disease: After cardiac surgery there is a frequent occurrence of acute kidney injury and NAC supplementation was found to significantly reduce this risk and the incidence of adverse cardiac events. However, there are no current guidelines established for the use, or not, of NAC in patients with kidney disease.
- Eye disease: NAC in the form of eyedrops is used in some ocular conditions, such as dysfunction of the meibomian gland, which generates ocular dryness, with symptoms such as itching, dryness, redness as well as flaking and crusting of the eyelids.
- Infectious diseases: By reducing mediators of oxidative stress and inflammation, NAC shows potential in the treatment of various infectious diseases, such as hepatitis, pulmonary tuberculosis, and chorioamnionitis – a serious bacterial infection of the membranes or tissue surrounding the fetus in pregnant women.
- Male infertility: Some studies have shown positive effects on the treatment of diseases caused by oxidative stress in the male reproductive system, where NAC treatment for three months showed improved sperm count and motility.
- Cancer: NAC has shown promising results, although in small studies, to reduce the growth, migration, and invasion of cancer cells in different types of cancer, as well as improving the quality of life of patients undergoing radiation therapy.
- Gastrointestinal diseases: Due to its ability to act as an antioxidant, NAC has shown promising results when used in different gastrointestinal conditions such as bacterial infections and inflammation.
- Lung diseases: Inflammation and increased oxidative stress during the progression of respiratory diseases, such as chronic obstructive pulmonary disease and cystic fibrosis, and the resulting reduction in antioxidants has highlighted the promising role that NAC may play as a therapeutic agent for the treatment of these diseases, due to its antioxidant and anti-inflammatory properties, as well as its proven ability to reduce mucus production and viscosity.
Conclusion:
NAC is a medication and dietary supplement which can help to boost cysteine levels, allowing the body to make more of the important antioxidant, glutathione.
While taking NAC as a supplement shows promising results to help improve the symptoms of a number of medical conditions, it is important to note that the majority of the research into NAC supplementation was done in small studies and clinical trials, as well as in laboratory and animal studies.
There is ongoing research to determine the full extent of the benefits of supplementing with NAC.
References:
N-Acetylcysteine (NAC): Impacts on human health. Published June 2021 in the journal Antioxidants (Basel). PubMed Central. National Centre for Biotechnology Information. US National Library for Medicine. National Institutes of Health. USA. (www.ncbi.nlm.nih.gov)
A review on various uses of N-Acetylcysteine. Published in Cell Journal V.19(1) Apr-Jun 2017. PubMed Central. National Centre for Biotechnology Information. US National Library for Medicine. National Institutes of Health. USA. (www.ncbi.nlm.nih.gov)
What are the benefits of NAC (N-Acetylcysteine)? Published online and updated 11April 2023. Medical News Today. (www.medicalnewstoday.com)
A review of the use of N-Acetylcysteine (NAC) in clinical practice. Published 6 October 2021. Natural Medicine Journal. (www.naturalmedicinejournal.com)
NAC (N-Acetylcysteine): Benefits, side effects, and more. Published online and updated 5 January 2024. Forbes Health. (www.forbes.com)
Health benefits of NAC. Published online and reviewed 25 June 2024. WebMD. (www.webmd.com)
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