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N-acetylcysteine, covid, cancer and respiratory illness

N-acetylcysteine, NAC, covid, cancer, respiratory, illness, amino acid L-cysteine, Cysteine, AIDS, Liver Toxicity, Chronic lung disease, ‘flu, Chronic lung disease, Cancer, FDA
N-acetylcysteine covid, cancer and respiratory illness

N-acetylcysteine (NAC) reduces oxidative stress and is used as an antidote for paracetamol overdose; it may also reduce DNA damage and help fight influenza, COPD, AIDS, cancer and Covid. It is sold over-the-counter as a decongestant.

NAC is an antioxidant derived from the amino acid L-cysteine and is marketed for its immune boosting and liver-protective properties. It is also sold over the counter in the UK to reduce cold symptoms like wheezing, coughing and mucous. Yes, it is a common cold remedy.


L-Cysteine is an amino acid and is involved in many enzymatic reactions, also having an important structural role in many proteins.

Cysteine contains sulphur and is a non-essential amino acid being produced from methionine. So, you can make it in your body – you don’t have to consume it.

A large amount of clinical work has been completed by the University of Michigan Health System. They conclude that:

  • L-cysteine combines in the body with glycine and glutamic acid, to make glutathione(GSH) particularly when there is an acute shortage in the body, for example in times of high oxidative stress caused by illness.
  • Glutathione deficiencies have also been linked with male infertility, cataracts, diabetes, liver disease, depression, respiratory and pulmonary disease, and cancer.

NAC can be taken as a dietary supplement and is used in a number of ways. For example:


Several clinical trials suggest that people who are HIV+ve have low levels of cysteine and glutathione and NAC supplementation can correct this. It is believed NAC also boosts immune function.

Liver Toxicity

NAC is known to be an effective treatment for acetaminophen (Tylenol or Paracetamol poisoning), which can be life-threatening. Doctors use NAC Intravenously. There is some evidence that it may reduce chemotherapy toxicity and damage.

Chronic lung disease 

Some studies show that NAC may reduce inflammation in the lungs and improve lung function. There is a thorough meta-analysis on NAC benefits in chronic Pulmonary Disease (COPD) by the People’s Hospital of Zhejiang in China.


NAC may prevent precancerous conditions, and help detoxify the liver. It may also have a direct and restricting effect on cancer tumours.

There is also a pilot study from the Sidney Kimmel Cancer Centre showing that the use of common over-the-counter decongestant NAC used at maximum dose has anti-proliferative effects in breast cancer (1) between diagnosing and surgery. A transporter, MCT4, bring fuel to the tumour was 80% blocked by this antioxidant, and a cancer marker K167 fell 25%.

Covid-19 and common ‘flu

A deficiency of glutathione is common in people with ‘flu, and researchers at the Nuffield, Oxford have reviewed the benefits of NAC in an overview (2). The main research study on NAC benefit on preventing respiratory influenza is found in a 1997 review (3). Here people took it for 6 months prior to flu season and had a simply massive betterment that a flu vaccine and an even better record than dosing with vitamin D.

Not surprisingly, there is a deficiency in people with Covid, because they seem short of glucose 6-phosphate dehydrogenase. NAC helps overcome certain respiratory issues, improves T-cell levels which reducing inflammation and cytokine levels. Research suggests high dose NAC can greatly reduce the risk of a cytokine storm and increase survival.

NAC has been shown to inhibit influenza virus replication(4).

Dose of NAC?

Clinical studies usually use 200 mg/day as an effective dose, but NAC may cause stomach upset, low blood pressure, drowsiness and headaches in a small percentage of cases, so be aware of this.

The FDA and NAC

The FDA is currently reviewing NAC with a view to ending over-the-counter sales.

Go to: Common decongestant NAC can fight cancer


  1. Metabolic and anti-proliferative effects of in vivo anti-oxidant NAC supplementation with breast cancer; 2017; Daniel Monti et al.
  2. https://www.cebm.net/covid-19/n-acetylcysteine-a-rapid-review-of-the-evidence-for-effectiveness-in-treating-covid-19/
  3. https://erj.ersjournals.com/content/10/7/1535.long
  4. https://pubmed.ncbi.nlm.nih.gov/19732754/
  5. https://www.tandfonline.com/doi/abs/10.3109/15412555.2013.858315