Benefits, Uses, Side Effects, and More

NAC supplements may offer health benefits like easing symptoms of certain mental health disorders, reducing hyperactivity and irritability, and promoting healthy aging. NAC stands for N-acetylcysteine. It is the supplement form of cysteine, a non-essential amino acid that converts into the antioxidant glutathione in the liver. As an amino acid, cysteine also acts as a building block for proteins.

Many benefits of NAC supplements are still being researched.  

NAC supplementation is being studied for the treatment of several psychiatric disorders. A research review examining this connection found that a dose of 2000-2400 mg per day of NAC orally may be an effective adjunct treatment for schizophrenia and substance use disorders. 

Researchers attribute this benefit to NAC’s anti-inflammatory and antioxidant effects that could improve brain health and modify neurological pathways. 

Some research has shown the benefits of NAC supplementation for people with autism spectrum disorder (ASD). An analysis of research found that eight to 12 weeks of NAC supplementation resulted in less hyperactivity and irritability and more social awareness in those with autism spectrum disorder (ASD).

While promising, the researchers noted a need for further evidence before recommendations can be made about using NAC as an adjunct therapy for ASD. 

Another analysis found that taking antioxidants, including NAC, improved scores on the aberrant behavior checklist in those with ASD. This included reduced irritability and hyperactivity; however, the effect was small. 

NAC may support healthy aging by helping to replenish intracellular glutathione, a powerful antioxidant inside cells. It’s thought that glutathione production decreases as we age, leaving cells susceptible to oxidative stress.

Research found that combining glycine and NAC supplementation improved some age-related health abnormalities in older adults. One small study showed reduced oxidative stress and systolic blood pressure, and increased gait speed and muscle strength. However, this study was small, and more research is needed to support these findings.

NAC supplements can come in the form of a pill, powder, or effervescent tablets.

Some forms of NAC may have an unpleasant smell, similar to sulfur or rotten eggs. You may want to take the supplement alongside a flavored drink to mask the smell and taste.

Dosage

There is no current standard dose for NAC supplements. Additionally, the bioavailability of NAC is low, meaning that it is not well absorbed by the body.

Speak to your healthcare provider for guidance before taking NAC, since these supplements are not yet permitted by the FDA. They can recommend a safe dose for you and how long to take it.

There have been no safety concerns reported on NAC supplement products.

However, there aren’t yet studies evaluating the safety of NAC among breastfeeding or pregnant individuals. Speak with a healthcare provider before taking NAC if you are pregnant or breastfeeding.

Potential Drug Interactions

NAC may interact with certain medications, including the following:

• Anti-hypertensive medications, or drugs to lower blood pressure. When taken together with NAC, they can cause your blood pressure to drop too low
• Anticoagulants or blood thinners, as NAC may amplify the effect of these medications
• Other herbs or supplements that lower blood pressure or act as blood thinners, such as L-arginine, niacin, stinging nettle, garlic, ginger, and ginkgo, among others 

What To Look For 

The FDA is not able to regulate supplements for safety and effectiveness in the same way it regulates food and medications.

When buying a supplement, look for a product that has undergone third-party testing for purity and potency. Reputable third-party testers include U.S. Pharmacopeia, NSF International, and ConsumerLab.com. 

When in doubt, you can always speak with a healthcare provider for product recommendations before starting a new supplement.

Can You Take Too Much NAC?

There is no established maximum recommended dose for NAC supplementation, so it’s important to speak with a healthcare provider before taking NAC. Make sure to follow the dosage recommendation on the supplement label unless your healthcare provider recommends otherwise.

There are a few potential side effects of NAC oral supplements. These include:

• Abdominal pain or discomfort
• Diarrhea
• Indigestion
• Nausea
• Vomiting

An inhaled, liquid form of NAC is a prescription drug approved by the U.S. Food and Drug Administration (FDA). Most commonly, NAC is used to treat acetaminophen (Tylenol) toxicity and certain respiratory conditions, including chronic obstructive pulmonary disease (COPD).

Since NAC is an FDA-approved drug, the use of NAC in dietary supplements is technically not permitted by the FDA. However, in August 2022, the FDA announced a consideration to change its stance on allowing consumer NAC supplements. The decision is still pending approval.

NAC is a derivative of the non-essential amino acid cysteine, which is a precursor to the antioxidant glutathione. A prescription drug form of NAC is FDA-approved, but the FDA does not yet permit the use of NAC in supplements. The FDA is currently in the process of updating its position on the topic.   

NAC supplements are being studied for their use in treating psychiatric disorders, reducing hyperactivity and irritability in those with ASD, and improving age-related health abnormalities. However, further research is necessary. If you’re interested in taking NAC, speak with a trusted healthcare provider before adding this new supplement to your regimen.