July 20, 2024

N-Acetyl Cysteine (NAC), a derivative of the amino acid cysteine, has gained considerable attention in the health and wellness community in recent years for its wide range of benefits, drawing attention from researchers and health enthusiasts alike. In 2022, NAC faced a period of controversy when the FDA temporarily banned its sale. The cause of this ban was rooted in the unique classification of NAC; having gained approval as a drug in 1963, the FDA stated that it could not be considered a conventional dietary supplement. This led to concerns regarding the safety, availability, and legitimacy of a supplement that had become integral to many. Later in 2022, the FDA revised its position, opting to allow the sale of NAC while establishing clear guidelines to ensure responsible marketing to prevent non-compliant disease claims.  

NAC stands as a versatile supplement with a myriad of health benefits that extend across physiological systems. Benefits of NAC supplementation are explored below and encompass antioxidant properties, respiratory impacts, liver support, and immune benefits.

Antioxidant Properties

NAC exhibits robust antioxidant properties, acting as a free radical scavenger to mitigate cellular damage associated with oxidative stress (1).  Free radicals are formed as byproducts of normal metabolic processes, but also through inflammatory and environmental exposures. Free radical accumulation, caused by an imbalance between their production and the body’s ability to neutralize them, can cause cellular damage and contribute to aging and various diseases (2). NAC can help reduce free radical accumulation and therefore mitigate oxidative stress caused by an imbalance between free radicals and antioxidants (3).

In addition to its own antioxidant capabilities, NAC has the capability to directly boost levels of the antioxidant, glutathione, in the body. Glutathione, a tripeptide composed of cysteine, glutamate, and glycine, serves as the body’s “master” antioxidant (4). Glutathione can donate electrons to free radicals, stabilizing them to reduce damage. Glutathione also plays a central role in the detoxification of harmful substances and can help repair oxidative damage (5). In addition to antioxidant defense and detoxification, other essential functions of glutathione include immune system support, cellular repair, energy production, and anti-inflammatory effects.

Maintaining optimal levels of glutathione is crucial for overall cellular health and resilience against oxidative stress, however, many factors can contribute to a decline in glutathione, including:

  • Aging: As we age, the body’s ability to synthesize and maintain optimal levels of glutathione may decrease (6).
  • Poor diet: A diet lacking in nutrients that are essential for glutathione synthesis, such as the amino acid cysteine, can contribute to lower glutathione levels. Individuals who eat primarily plant-based may be at risk of low glutathione levels as cysteine is primarily found in animal-based foods (7).
  • Chronic disease/infection/inflammation: These factors can lead to an increased demand for glutathione as the body works to combat oxidative stress and inflammation.
  • Environmental toxins: Toxins, air pollution, and heavy metals are examples that can increase oxidative stress and deplete glutathione (8).

Studies have shown that supplementation with NAC can raise glutathione levels. A study published in the American Journal of Respiratory and Critical Care Medicine demonstrated that NAC supplementation effectively increased glutathione levels in the lungs in patients with pulmonary fibrosis (9).

NAC has been successfully used to treat glutathione deficiency in a wide range of diseases, including HIV infection and Chronic Obstructive Pulmonary Disease (COPD), with no clinically significant adverse side effects (10).

The importance of maintaining glutathione levels are well researched. This is why we include NAC in vegan autoimmune diet as plant-based diets may consist of less sources of cysteine and could result in lower glutathione levels (11).

Respiratory Health: COPD and Mucus Regulation

NAC’s impact on respiratory health is noteworthy, especially in conditions like Chronic Obstructive Pulmonary Disease (COPD), a progressive lung disease characterized by airflow limitation. A systematic review and meta-analysis revealed that NAC can help improve symptoms in COPD patients and enhance overall lung function (12). Additionally, its mucolytic properties can contribute to the breakdown of mucus, making it easier to clear respiratory passages and improve lung function (13).

Liver Health: Detoxification and Overdose Reversal

Beyond respiratory health, NAC demonstrates promise in supporting liver function, particularly in the context of detoxification and acetaminophen overdose. The liver is responsible for metabolizing and detoxifying substances such as drugs, environmental toxins, and metabolic byproducts. A study in 2022 demonstrated that NAC, due to its ability to enhance glutathione, could protect the liver from oxidative damage, which can occur during normal metabolic processes (14). In situations such as acetaminophen (Tylenol) overdose, NAC is used as an antidote to prevent liver failure by replenishing glutathione levels. Acetaminophen is normally metabolized in the liver, but in excessive amounts, its metabolites can overwhelm the liver’s detoxification mechanisms and lead to liver injury (14). Treatment with NAC in situations of acetaminophen overdose can replenish glutathione levels and aid in the detoxification process, which can help prevent or reduce the extent of liver damage.

 Some studies suggest that NAC may even have a beneficial effect in non-alcoholic fatty liver disease (NAFLD), a condition characterized by the accumulation of fat in the liver. NAC’s antioxidant properties and its role in promoting glutathione synthesis may contribute to protecting the liver from inflammation and oxidative stress associated with NAFLD (15).

Immune Support in the Pandemic Era

In the face of recent global health challenges, the role of NAC in immune support has become a subject of interest. While research on its efficacy in addressing respiratory infections, including COVID-19, is ongoing, preliminary findings suggest that NAC could reduce the severity and duration of such infections by modulating immune responses and reducing oxidative stress (16). Another study showed that NAC can improve the clinical response of COVID-19 patients with serious illness compared to the control group (17). However, further research is needed to establish NAC’s role in treating COVID-19 definitively.


Extensive studies have shown that NAC, administered intravenously or orally, exhibits minimal side effects and is generally considered safe and well-tolerated at recommended doses (18). As ongoing research continues to unveil new findings on its effects, an informed approach, guided by healthcare professionals, positions NAC as a versatile supplement with robust scientific backing.

N-Acetyl Cysteine is a promising supplement with a robust scientific foundation supporting its various health benefits. From its role in mitigating oxidative stress to influencing liver health and immune responses, NAC’s versatility positions it as a valuable supplement in the pursuit of overall health.

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