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What is NAC's Role in The Body?

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What is NAC's Role in The Body?

N-Acetyl Cysteine, also known as NAC, is a potent, safe, inexpensive antioxidant drug. It is a versatile substance with various actions and uses. It is commonly used to help treat various conditions such as PCOS, preterm delivery, and ulcerative colitis. It can also help reduce the toxicity of acetaminophen and can even improve muscle performance. This article will discuss NAC, its role in the body, how to test for it, and the sources of NAC.


What is NAC?

NAC is a synthetic form of the non-essential amino acid l-cysteine. L-Cysteine is a precursor to glutathione, a dominant antioxidant. NAC, when taken orally, has a low bioavailability of 4-10% due to its processing in the small intestine and liver.

What is NAC's Role in The Body?

NAC is a powerful antioxidant. Antioxidants are molecules that neutralize free radicals, molecules that cause damage to cellular parts, including DNA. NAC is also a precursor to glutathione, one of the most powerful antioxidants. Through its own antioxidant capability and the increased production of glutathione, NAC can assist in detoxification pathways in the liver and protect endothelial cells (cells that line the heart, lymph, and blood vessels) from death. NAC is also a potent neutralizer of toxic chemicals. It can improve insulin sensitivity, decrease inflammation, and has a mucolytic (breaking down mucus secretions) function.

Because of these actions, NAC has been shown to be helpful in a variety of conditions, the most common and well-researched being the following:

Polycystic Ovarian Syndrome

Polycystic Ovarian Syndrome (PCOS) is the most common cause of infertility due to lack of ovulation. PCOS can come with symptoms of hirsutism (facial hair, dark hairs on the body), cycle irregularities, ovarian cysts, blood sugar dysregulation, and more. Clomid is a first-line drug therapy for women with PCOS, as it can help to induce ovulation. However, 40% of women that take Clomid are resistant to it, making it ineffective. Multiple studies have demonstrated that Clomid with concurrent NAC supplementation significantly increased the ovulation and pregnancy rate in PCOS women resistant to Clomid.

Preterm Delivery

Bacterial vaginosis infections can increase risk factors for preterm delivery. Inflammatory responses during these infections can increase the complexity of the infection. NAC can lower the inflammatory response during infections. Additionally, studies show that in women with previous preterm birth and bacterial vaginosis infection, NAC taken with progesterone, a hormone essential for pregnancy, after the 16th week of pregnancy can reduce the risk of preterm births and improve pregnancy outcomes.

Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is defined as the loss of 3 or more consecutive pregnancies within the first two trimesters (20 weeks). Compared to folic acid, a B vitamin essential for the development of the fetus, administration of both folic acid and NAC significantly increased the live birth rate.

Acetaminophen Toxicity

Acetaminophen is a pain and fever-reducing over-the-counter drug. Acetaminophen is the most commonly overdosed drug in pregnancy, and it is one of the most common causes of drug-induced liver toxicity in children and adults. The metabolite of acetaminophen causes liver damage that may lead to liver failure. NAC is the first-line therapy to treat acetaminophen-induced liver toxicity by reducing the harmful metabolite of acetaminophen, increasing glutathione levels which will also directly reduce the harmful metabolite, and utilizing its antioxidant capabilities to protect liver cells. NAC can reduce the harm done by acetaminophen-induced liver toxicity if given within 10 hours of overdose or eight hours of a severe overdose.

Ulcerative Colitis

Ulcerative colitis (UC) is a type of chronic inflammatory bowel disease (IBD) characterized by inflammation and ulceration in the inner lining of the large intestine. UC patients can have frequent bloody and mucus-filled loose stools, with rectal pain and weight loss, among other symptoms. NAC protects the cells of the colon from inflammation while simultaneously modulating the inflammatory response. NAC was also shown to increase the recovery rate of the colonic cells and colonic lining.

Muscle Performance

NAC has been shown to lessen fatiguing of the muscles. A study showed that NAC increased the forced output of muscle by 15% after 3 minutes of repetitive contractions.

How to Test NAC Levels

Since NAC is converted into l-cysteine, there is no test to check NAC levels directly. NAC can be indirectly assessed through testing cysteine and glutathione levels.


Checking cysteine levels can indirectly assess the need for NAC, as cysteine levels can be increased from NAC. Cysteine can be tested through amino acid profiles such as the Plasma Amino Acids by Doctor's Data (cystine, the extracellular form of cysteine, is found on this test) and Urine Amino Acids - FMV by Doctor's Data.


Since NAC can increase glutathione levels, low glutathione may warrant NAC ingestion. Glutathione can be tested in the blood as a single marker, such as the glutathione test by Doctor's Data. Like cysteine, it can also be found on the Spectracell Laboratories micronutrient test discussed above.

Sources of NAC


While no dietary sources of NAC exist, cysteine is found in foods such as chicken, turkey, eggs, yogurt, and garlic.


Per WebMD: "Although many dietary supplement products contain NAC, the US FDA has stated that it's illegal for dietary supplements to contain NAC since it's technically an approved drug. But as of August 2022, the FDA is considering changing this stance. It may allow for NAC in dietary supplements as long as no safety issues come up. A final decision is pending. Prescription NAC products are available under the guidance of a healthcare provider."


NAC is used as a drug that can be taken in the form of inhalation, intravenous (IV) solutions, and oral medications. Oral doses are in the range of 600 -1200 milligrams daily.



NAC is a powerful antioxidant on its own, but its ability to convert into another one of the most powerful antioxidants, glutathione, makes it even more credible. While there is no way to test for NAC, cysteine and glutathione levels may be utilized to assess if NAC may be helpful.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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