What is N-acetylcysteine used for?

Cysteine is an amino acid that is used as a building block in our bodies to make proteins. We consume cysteine in our diets through protein-rich foods, like beef or lentils. N-acetylcysteine is a chemical derivative of cysteine. This means which means that N-acetylcysteine contains one change in its chemical structure that distinguishes it from cysteine. N-acetylcysteine is often taken as a supplement. It is also used clinically by doctors to treat patients experiencing acetaminophen ( also known as Tylenol or paracetamol) overdose and some respiratory conditions such as bronchitis.

Companies that sell N-acetylcysteine as a supplement claim that it can prevent or treat many health ailments, such as cancer, liver disease, diabetes, high cholesterol, and psychiatric disorders like depression. Some clinical trials have been conducted to test if N-acetylcysteine can truly help with these illnesses, but the results have been mixed and inconclusive.

Some of this variability could come from the way N-acetylcysteine was given to the participants (orally, nasally, or intravenously) and the dosage amount. While N-acetylcysteine is safe to consume, it’s worth noting that some participants in these trials have had more adverse effects than placebo groups. They weren’t serious, but usually consisted of nausea and headache.

How does our body utilize N-acetylcysteine?

The main way N-acetylcysteine is thought to provide a therapeutic effect in the body is by acting as an antioxidant. Antioxidants are substances that prevent or slow the damage that can be caused to cells by free radicals, which are also known as reactive oxygen species. Free radicals are molecules that have an unpaired electron. This causes free radicals to be unstable because they want to “steal” an electron from a nearby molecule so that their unpaired electron will have a partner. If left unchecked, free radicals could damage cell components like lipids and nucleic acids (like DNA) through this process.

Fortunately, our body has antioxidant defenses to prevent this damage as they can neutralize free radicals. One of the main antioxidants our body uses is glutathione. To produce glutathione, a cysteine molecule is required. N-acetylcysteine can provide that cysteine to increase the levels of glutathione. This may be helpful for diseases where oxidative stress is involved in disease pathology, like in neurodegenerative or heart diseases. Oxidative stress occurs when there is an imbalance between free radicals and antioxidants, leading to an accumulation of free radicals.

Has N-acetylcysteine ever been tested as a treatment for Spinocerebellar ataxia (SCA)?

There have not been any clinical trials conducted to test the effect of N-acetylcysteine on any of the spinocerebellar ataxias. The only experimental data that exists is from a study in 2003 that used a cell model for SCA1, where researchers found that N-acetylcysteine had a positive effect on cell traits associated with SCA1. However, there have been some clinical trials in other neurodegenerative diseases. Oxidative stress in the brain is commonly seen in many neurodegenerative diseases, including many types of spinocerebellar ataxia and Parkinson’s disease.

Several clinical trials have been done in Parkinson’s disease to determine if N-acetylcysteine can help improve symptoms, but there have been some conflicting results that may be due to the way N-acetylcysteine was administered. When participants took N-acetylcysteine only orally, there was no effect on symptoms and brain scans did not show increased antioxidant levels. However, in a trial where oral was combined with intravenous administration, some positive effects on symptoms and biomarkers were found. You can learn more about this study at this link. More information about this study can be found here.

For now, we cannot make conclusions that N-acetylcysteine would have the same effect for all neurodegenerative diseases, but it does have potential that should be explored by researchers in spinocerebellar ataxias.

If you would like to learn more about N-acetylcysteine, take a look at this resource by the Memorial Sloan Kettering Cancer Center.

Snapshot written by Nola Begeja and edited by Dr. Gulin Oz.