NAC (N-acetylcysteine)

What Is It?
Health Benefits
Dosage Information
Guidelines for Use
General Interaction
Possible Side Effects
Evidence Based Rating Scale

What Is It?

Produced by the body, N-acetylcysteine (commonly called NAC) is a form of the amino acid cysteine. Because it enhances the production of the enzyme glutathione, one of the body's powerhouse antioxidants, NAC can both stave off disease and play an important role in boosting the immune system. Studies have shown that glutathione levels are often reduced in people with certain conditions related to the immune system.

For more than three decades, NAC has been used as a mucolytic ("mucus dissolving") agent to help break up the thick mucus often present in people suffering from chronic respiratory ailments. When administered intravenously, NAC has also proved invaluable in the treatment of acetaminophen overdose; it appears to protect the liver from this potentially toxic substance. Now widely available in supplement form, NAC is currently being recommended for preventing and treating a wide variety of ailments that may respond to its antioxidant properties. 

Health Benefits

Supplemental antioxidants--NAC is one of many-- are believed to protect the body's cells from altered oxygen molecules called free radicals. Damage from free radicals is thought to be a signficant factor in such degenerative conditions as cancer and heart disease. Of course, factors other than oxidative damage, such as life style factors and genetic susceptibility, play strong roles in disease development as well. The hope is that by reducing susceptibility to free radical damage, a person may further lower susceptibility to a variety of chronic medical conditions. Incidentally, it is by means of its antioxidant actions that NAC helps the liver eliminate potentially dangerous environmental and biological toxins from the body.

Specifically, NAC may help to:

  • Reduce congestion related to sinusitis, bronchitis, asthma, and other respiratory diseases. Conventional physicians routinely use NAC to dilute thick mucus, making it much easier to cough up or drain from the nasal passages and other congested areas. It's often used to ease congestion in people with pneumonia and other chronic respiratory diseases (1, 2). It has even been shown to reduce mucus secretions in people who smoke or who are regularly exposed to secondhand smoke (3). Outcomes have not been as promising in the treatment of chronic obstructive pulmonary disease (COPD). Twenty-five patients administered NAC in addition to conventional medical treatments for COPD, did not show improved measure of breathing or earlier hospital release (4). Ask your doctor to assess whether adding NAC to your diet may be helpful in your condition.
  • Prevent damage from diabetic nephropathy. The end products of lipid oxidation cause nerve and kidney damage. Treatment with strong antioxidants such as NAC may help prevent or reduce the severity of diabetic nephropathy (5).
  • Treat HIV-infected individuals. Some studies have shown that NAC interferes with the replication of certain viruses, including the HIV (human immunodeficiency virus) responsible for causing AIDS. Just what this means for HIV-infected individuals remains unclear, however. Because NAC can boost glutathione production, it supports the proper functioning of immune-system components such as T cells, B cells, and phagocytes, all of which are important for maintaining the body's defenses and potentially protecting against AIDs-related illnesses such as pneumonia (6, 7). 
  • Lessen flu symptoms. By thinning mucus and weakening the flu virus, supplemental NAC could potentially lessen the severity and duration of the flu. In a study of 262 elderly participants only 25% of the NAC treated group developed the flu symptoms compared to 79% of the group receiving placebo (8).
  • Prevent heart disease. In some studies, NAC appears to significantly lower levels of homocysteine and possibly lipoprotein(a), substances associated with an increased risk of heart disease. As an antioxidant, it also helps prevent the damaging oxidation--and thereby the precipitation--of LDL ("bad") cholesterol from the material that lines blood vessels (9). More research in this area is needed, however.
  • Delay age-related cataracts and macular degeneration. Both of these conditions have been associated with damage from oxygen free radicals. By boosting antioxidant activity in the eye's lens and macula, NAC may have a role to play in preventing cataracts (which cause the lens to become cloudy) and macular degeneration (which can result in blindness as this area of the retina deteriorates) (10).
  • Counter environmental toxins. NAC-supported glutathione interacts with the dangerous byproducts of many toxic substances, promoting their excretion through the liver. These substances include carbon tetrachloride, chloroform, and carbon monoxide; alcohol; such heavy metals as mercury, chromium, and boron; and the microorganisms aflatoxin and Eschicheria coli.
  • Lessen the risk of cancer. By helping to rid the body of environmental toxins and by fighting free radicals, NAC, at least theoretically, may have a role to play in preventing cancer (11). NAC might also slow the growth of cancerous tissues in these ways. Clinical trials are underway to explore this possibility. Interestingly, one study did find that NAC reduced adverse reactions to chemotherapy (12).
  • Slow the progression of multiple sclerosis. One theory regarding the cause of this degenerative condition attributes it to free-radical damage caused by low levels of glutathione (13). If this is true, NAC's antioxidant actions may be of help in protecting nerve cells from such damage. More research on NAC's effect on this disease is clearly needed.
  • Affect the course of Parkinson's disease. Parkinson's disease is often marked by reduced quantities of glutathione in the brain. In theory, boosting glutathione with NAC supplements could slow loss of function in Parkinson's (14, 15). NAC's antioxidant actions might also help by minimizing age-related deterioration of the nervous system.

Note: Antioxidants in general and NAC in particular have been considered useful for a number of other disorders. For information on these additional ailments, see our Dosage Recommendations Chart for NAC. 


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Dosage Information

Special tips:

--Regular supplementation with NAC will increase the urinary excretion of copper, a mineral. So if you're using NAC for an extended period of time, it's probably wise to add both copper (2 mg a day) and zinc (30 mg a day) to your treatment regimen.

--If you use NAC for more than a month, add a mixed amino acid complex to your treatment regimen to ensure that you are getting adequate, balanced amounts of all the amino acids.

--NAC is also available as an intravenous solution and inhalant, but by prescription only. Follow doctor recommendations regarding dosage and administration of these forms.

  • For the majority of ailments mentioned: Take 500 mg three times a day.

  • For bronchitis: For acute bronchitis, take 500 mg three times a day between meals. For chronic bronchitis, take 250 mg three times a day between meals.

  • For sinusitis: Take 500 mg twice a day between meals.

  • For multiple sclerosis: Take 500 mg three times a day every other day between meals; alternate with 30 mg zinc and 2 mg copper.

    Be sure to check out our Dosage Recommendations Chart for NAC, which lists therapeutic dosages for specific ailments at a glance.

  • Guidelines for Use

  • NAC is most effective when taken on an empty stomach.

  • If you've added a mixed amino acid complex to your NAC regimen, be sure to take it on an empty stomach as well, but at a different time of day than you take the NAC.

  • General Interaction

  • There are no known drug or nutrient interactions associated with NAC.

    For information on interactions with specific generic drugs, see our WholeHealthMD Drug/Nutrient Interactions Chart.

  • Possible Side Effects

  • NAC has no side effects as long as it is taken in the recommended dosage.

  • High doses of oral NAC may cause gastrointestinal problems, such as vomiting, or in rare cases a rash possibly accompanied by fever.

  • Cautions

  • Scientists must still determine how much NAC and glutathione can be safely absorbed and processed by the body.

  • Evidence indicates that in some healthy individuals, high doses of NAC (2,800 mg a day) can act as a pro-oxidant rather than an antioxidant, actually lowering levels of glutathione rather than increasing them. For this reason, otherwise healthy individuals may want to avoid taking high doses of NAC until more information is available.

  • Because there are no adequate studies of NAC in pregnant women, it's not recommended for women who are or may be pregnant.
  • Evidence Based Rating Scale

    The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.







    Several studies indicate efficacy as preventative and long-term treatment. Some conflicting evidence exists. More research is needed. (15-18)











    Conflicting results with different conditions. Ask your doctor about using NAC for this.













    Animal studies support this use. More research is needed before this can be recommended.













    Efficacy demonstrated after exposure to various environmental toxins. Ask your doctor about specific toxins.





    Flu symptoms






    Date Published: 04/19/2005

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