What is NAC and how can it benefit your health? (2024)

Medically reviewed by Carmen Pope, BPharm. Last updated on March 10, 2023.

Official answer

by Drugs.com

NAC (N-acetyl cysteine) helps replenish glutathione – which is an antioxidant that rapidly depletes during times of oxidative stress. NAC may help with fertility, brain health, heart health, and long-term respiratory conditions (such as Asthma or COPD), and reduce the risk of developing certain cancers. In medicine, NAC has been used as an antidote to acetaminophen overdose since the 1960s and to treat those with acute liver failure.

Any condition that causes inflammation, increased generation of free radicals, or depletes glutathione directly could potentially benefit from NAC supplementation. Glutathione deficiency may be recognizable through nonspecific symptoms such as premature aging, reduced immune function, fatigue, or an overall decrease in health.

Antioxidant effects

NAC is one of the most widely used antioxidants in clinical studies, although the exact way it works remains poorly understood. Some believe its main antioxidant benefits are due to it being a precursor to the semi-essential amino acid cysteine, increasing its levels to ensure the production of glutathione by the liver.

Does NAC help with COVID-19?

People with severe COVID-19 have increased levels of free radicals and often present with glutathione depletion, which can precipitate a cytokine storm. NAC also possesses anti-inflammatory activity and immune-modulating characteristics in addition to its antioxidant activity.

Research has shown that supplementation with NAC was associated with significantly lower mortality in people with severe COVID-19 than with no supplementation. It is thought NAC administration may suppress replication of the SARS-CoV-2 virus and improve outcomes if administered promptly. In combination with antiviral agents, it may also reduce hospital admission and mechanical ventilation rates.

How does NAC work?

NAC is converted to cysteine in the body and then converted again to glutathione. Cysteine is considered a semi-essential or conditional amino acid because its production depends on levels of two other amino acids, serine and methionine. If body levels of these two amino acids are low, then levels of cysteine will be low and dietary supplementation with cysteine (or its precursor, NAC) essential. Without cysteine, our bodies cannot make glutathione, and levels of this important antioxidant become depleted, which can compromise the immune response and cause oxidative damage to important organs and tissues.

Are there any side effects of NAC?

NAC has a wide safety margin and generally a low risk of side effects.

Only a small subset of patients administered oral NAC report side effects such as nausea, vomiting, and heartburn, and dosages of up to 8000 mg/day are considered safe. Data from trials indicate that when cysteine is delivered in a non-toxic form (ie, as NAC), side effects are negligible.

What foods contain NAC?

NAC is not found in food, but cysteine is. Cysteine is a sulfur-containing amino acid that is essential for the production of glutathione. Foods with high levels of cysteine include:

Broccoli
Brussel sprouts
Cabbage
Dates
Egg yolks
Garlic
Ginseng
Legumes, such as chickpeas and lentils
Meat, such as beef, chicken, duck, or pork
Milk and dairy products
Onion
Red bell peppers
Seafood, such as hake, monkfish, or tuna
Soy and soy products (eg, tofu, tempeh)
Sunflower seeds
Wheat germ
Yeast.

What is the relationship between glutathione and NAC?

NAC is converted in the body to cysteine which is then used with two other amino acids, glycine, and glutamic acid to make glutathione.

NAC is the supplemental form of cysteine that is less toxic and more easily absorbed.

Why is glutathione important?

Research has shown that the presence of glutathione prevents cell damage by free radicals due to oxidative stress. Free radicals are unstable oxygen-containing molecules that are made by the body during normal metabolic processes. In most circ*mstances, the body can make enough antioxidants to neutralize these free radicals. Oxidative stress happens when there are too many free radicals circulating in the body for the number of antioxidants present.

Long-term oxidative stress has been shown to contribute to many health conditions, including diabetes, cancer, and heart disease.

Glutathione is naturally made by our liver and consists of three different amino acids – cysteine, glutamine, and glycine.

If I take NAC do I need to take glutathione as well?

NAC appears a much more effective way of increasing glutathione levels in the body than taking glutathione itself. Glutathione is poorly absorbed and may be broken down by enzymes in the stomach. Taking glutathione long-term as a supplement has also been associated with lower zinc levels

In contrast, few side effects have been reported with NAC compared with glutathione.

Why are NAC supplements better than cysteine supplements?

Because NAC contains an acetyl group, it is less reactive than cysteine. This makes it less susceptible to oxidation, less toxic, more soluble in water, and more easily absorbed. Once ingested orally, NAC is readily absorbed through the stomach and intestine and sent to the liver where it is almost entirely converted to cysteine. Overall NAC is a better source of cysteine than cysteine itself given by injection. The majority of cysteine is converted by the liver into glutathione.

References

Šalamon, Š., Kramar, B., Marolt, T. P., Poljšak, B., & Milisav, I. (2019). Medical and Dietary Uses of N-Acetylcysteine. Antioxidants (Basel, Switzerland), 8(5), 111. https://doi.org/10.3390/antiox8050111
Shi, Z., & Puyo, C. A. (2020). N-Acetylcysteine to Combat COVID-19: An Evidence Review. Therapeutics and clinical risk management, 16, 1047–1055. https://doi.org/10.2147/TCRM.S273700
Pol, Stanislas et al. N-acetylcysteine for paracetamol poisoning: effect on prothrombin. The Lancet, Volume 360, Issue 9340, 1115
Kwon, D. H., Cha, H. J., Lee, H., Hong, S. H., Park, C., Park, S. H., Kim, G. Y., Kim, S., Kim, H. S., Hwang, H. J., & Choi, Y. H. (2019). Protective Effect of Glutathione against Oxidative Stress-induced Cytotoxicity in RAW 264.7 Macrophages through Activating the Nuclear Factor Erythroid 2-Related Factor-2/Heme Oxygenase-1 Pathway. Antioxidants (Basel, Switzerland), 8(4), 82. https://doi.org/10.3390/antiox8040082
Kwon, D. H., Cha, H. J., Lee, H., Hong, S. H., Park, C., Park, S. H., Kim, G. Y., Kim, S., Kim, H. S., Hwang, H. J., & Choi, Y. H. (2019). Protective Effect of Glutathione against Oxidative Stress-induced Cytotoxicity in RAW 264.7 Macrophages through Activating the Nuclear Factor Erythroid 2-Related Factor-2/Heme Oxygenase-1 Pathway. Antioxidants (Basel, Switzerland), 8(4), 82. https://doi.org/10.3390/antiox8040082
Ezeriņa, D., Takano, Y., Hanaoka, K., Urano, Y., & Dick, T. P. (2018). N-Acetyl Cysteine Functions as a Fast-Acting Antioxidant by Triggering Intracellular H2S and Sulfane Sulfur Production. Cell chemical biology, 25(4), 447–459.e4. https://doi.org/10.1016/j.chembiol.2018.01.011
Khoshbaten, M., Aliasgarzadeh, A., Masnadi, K., Tarzamani, M. K., Farhang, S., Babaei, H., Kiani, J., Zaare, M., & Najafipoor, F. (2010). N-acetylcysteine improves liver function in patients with non-alcoholic Fatty liver disease. Hepatitis monthly, 10(1), 12–16.
Atkuri, K. R., Mantovani, J. J., Herzenberg, L. A., & Herzenberg, L. A. (2007). N-Acetylcysteine--a safe antidote for cysteine/glutathione deficiency. Current opinion in pharmacology, 7(4), 355–359. https://doi.org/10.1016/j.coph.2007.04.005
Aitio M. L. (2006). N-acetylcysteine -- passe-partout or much ado about nothing?. British journal of clinical pharmacology, 61(1), 5–15. https://doi.org/10.1111/j.1365-2125.2005.02523.x
Banerjee, S., & McCormack, S. (2019). Acetylcysteine for Patients Requiring Mucous Secretion Clearance: A Review of Clinical Effectiveness and Safety. Canadian Agency for Drugs and Technologies in Health.
Di Marco, F., Foti G., Corsico, A.G. Where are we with the use of N-acetylcysteine as a preventive and adjuvant treatment for COVID-19? Eur Rev Med Pharmacol Sci. 2022. Vol. 26 - N. 2. 715-721 DOI: 10.26355/eurrev_202201_27898

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Drug information

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NAC

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