N-Acetyl Cysteine Fact Sheet

About N-Acetyl Cysteine

N-acetyl cysteine (NAC), is a highly absorbable form of cysteine, an amino acid, or component of protein. The human body synthesizes NAC from methionine (which must be obtained from the diet) and serine.

N-acetyl cysteine is a frequently utilized as a mucolytic treatment option in conventional medicine for clearing the lungs in respiratory diseases. It also regulates COX-2, the enzyme that manages pain and inflammation in many chronic health conditions and can help prevent side effects caused by drug and toxic chemical reactions, including acetaminophen overdose. N-acetyl cysteine supports the body’s free radical scavenging resources as a precursor to glutathione, one of the more powerful antioxidants.

N-acetyl cysteine disease prevention and health effects include:

  • Lung health
  • Gastrointestinal health
  • Obsessive-compulsive disorder

Obsessive-compulsive disorder, or OCD, is a mental health condition in which a person repeats a particular behavior, such as hand washing or house cleaning, excessively. This may be accompanied by irrational thoughts. The disorder is often significant enough to interfere with normal activities. According to a World Health Report study, OCD causes 2.5% of total healthy years lost due to disease worldwide. The disease is accompanied by an abnormally high level of glutamate in the brain, the most abundant excitatory neurotransmitter, and researchers have found that NAC can lower the level of glutamate and reduce oxidative stress and inflammation that are also related to OCD. The supplement has demonstrated effectiveness (1 and 6) in treating both obsessive hair pulling (trichotillomania) and compulsive nail biting (onychophagia).

N-Acetyl Cysteine and Aging

Chronic obstructive pulmonary disease, or COPD, is an umbrella term for respiratory illnesses, such as pneumonia and bronchitis that currently affect 64 million people worldwide. COPD lung infections cause shortness of breath and a low oxygen level, reducing the body’s ability to fight diseases and causes secondary health conditions, such as sleep apnea. A study has demonstrated that taking a 600 mg N-acetyl-cysteine supplement two times per day for 2 months stabilizes breathing in COPD cases (9).

The body’s digestive capacity becomes less effective as people age, and issues include low stomach acid, gastroenteritis and infrequent bowel elimination. Improving the quality of digestion has the tangential effect of making nutrients more available to all of body’s systems and processes, which contributes to numerous health benefits.

Ulcerative colitis is an inflammatory bowel disease that affects the colon and causes diarrhea, weight loss, and intestinal bleeding. If left untreated, it could develop into a fistula, or abnormal opening in the intestinal lining. Researchers believe that when the body fights ulcerative colitis, the white blood cells destroy the microorganisms that accumulate at the irritation site, which produces hydrogen peroxide free radicals that worsen the condition. NAC is a complementary treatment for Mesalamine, the standard prescribed medication for treating ulcerative colitis. It stimulates the production of the antioxidant glutathione that neutralizes the hydrogen peroxide (10).

Oxidation is an additional age-related disease precursor, which environmental pollutants and the over-burdening of the body’s natural stores of antioxidants exacerbate. Healthy cells are damaged when oxygen circulates in the body, and the resulting free radicals are normally neutralized by the body’s antioxidant defense system. In modern times, however, the sheer high-level load of toxins in the environment resulting from stress increases the number of free radical induced mutations in healthy DNA, which if left untreated replicate and develop disease. To compensate for the extra oxidation damage, supplementing with dietary or nutraceutical antioxidants is necessary for preventing disease. NAC is a minor scavenger of reactive oxygen species but its principal antioxidant role is in reviving glutathione, one of the most powerful antioxidants in the body, when it becomes depleted. Glutathione helps to restore the cells’ ability to fight damage and prevent chronic disease.

How Can I Add N-Acetyl Cysteine to My Diet?

Cottage cheese, ricotta, yogurt, pork, turkey, chicken, duck, lunch meat, oat flakes, granola and wheat germ.

Supplementing with N-Acetyl Cysteine

N-acetyl cysteine is available in powder, tablet or topical solution forms. N-acetyl cysteine aerosol spray for the treatment of pulmonary disease can be prescribed by a physician.

How Much N-Acetyl Cysteine Should I Take?

A standard dosage is typically 250–1,500 mg per day. For respiratory illness: 200 mg, two times per day and for antioxidant protection and general health: 500 mg per day

Side Effects

Taking N-acetyl cysteine as a nutritional supplement may result in the following side effects:

  • Nausea
  • Vomiting
  • Headache
  • Dry mouth
  • Dizziness
  • Abdominal pain
  • An excess amount – 1.2 g or more – could cause oxidative stress.

Taking it for an extended period can lead to urinary zinc excretion, and supplementing with zinc and copper would be necessary.


An N-acetyl cysteine supplement may contraindicate with the following medications:

  • Nitroglycerin and isosorbide
  • Activated charcoal
  • Medications that suppress the immune system , including azathioprine (Imuran), cyclophosphamide (Cytoxan) or prednisone (Deltasone)
  • Oxiconazole


  1. Ayuso-Mateos, Jose Luis. Global Burden of Obsessive-Compulsive Disorder in the Year 2000. 21 Aug 2006. http://www.who.int/healthinfo/statistics/bod_obsessivecompulsive.pdf
  2. Memorial Sloan-Kettering Cancer Center. “N-Acetylcysteine.” 9 Apr 2013.
  3. University of Maryland Medical Center. “Cysteine.” 1 May 2011.
  4. Drweil.com. “NAC or N-Acetyl L-Cysteine for OCD?” 13 Jan 2012.
  5. University of Michigan Health System. “N-Acetyl Cysteine.”
  6. Camfield, David A., et al. Progress in Neuropsychopharmacology and Biological Psychiatry. “Nutraceuticals in the Treatment of Obsessive Compulsive Disorder (OCD): A Review of Mechanistic and Clinical Evidence.” 1 June 2011. http://www.ncbi.nlm.nih.gov/pubmed/21352883
  7. Sarrisa, Jerome, et al. Journal of Affective Disorders. “Complementary Medicine, Self-Help, and Lifestyle Interventions for Obsessive Compulsive Disorder (OCD) and the OCD Spectrum: A Systematic Review. May 2012. http://www.ncbi.nlm.nih.gov/pubmed/21620478
  8. World Health Organization. “Living with Chronic Lung Diseases.”
  9. Rahman, Irfan. International Journal of Chronically Obstructive Pulmonary Diseases. “Antioxidant Therapies in COPD.” 2006 March. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706605/
  10. Guijarro, L.G., et al. World Journal of Gastroenterology. “N-acetyl-L-cysteine Combined with Mesalamine in the Treatment of Ulcerative Colitis: Randomized, Placebo-Controlled Pilot Study.” 14 May 2008. http://www.ncbi.nlm.nih.gov/pubmed/18473409
  11. Dodd, Seetal, et al. Expert Opinions in Biological Therapy. “N-acetylcysteine for antioxidant therapy: pharmacology and Clinical Utility.” 2008. http://www.ncbi.nlm.nih.gov/pubmed/18990082


Last Reviewed: 27-Jan-2014

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Whilst wielding a couple of dumbbells in a gym class in 2003, Kate experienced an epiphany around the lack of accepted best practice guidelines when it came to staying well and avoiding disease. Kate realized that she had no chance of slowing her own aging process unless she became better educated about her options.

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