L-Acetyl n-Cysteine (commonly referred to as NAC, which is N-acetylcysteine) has significant scientific support for its use in supporting the mucus membranes, particularly in the respiratory tract. NAC is a precursor to glutathione, a powerful antioxidant, and acts directly as a mucolytic agent. Numerous clinical studies have demonstrated that NAC can break disulfide bonds in mucus glycoproteins, thereby decreasing mucus viscosity and making it easier to clear from the airways. This mucolytic effect has made NAC a standard therapy in conditions characterized by thick, excessive mucus, such as chronic bronchitis, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. For example, a 2015 systematic review in Respiratory Medicine concluded that long-term NAC use reduces the frequency of exacerbations in chronic bronchitis and COPD patients.

In addition to its mucolytic properties, NAC’s antioxidant activity may help protect the mucus membranes and respiratory epithelium from oxidative stress and inflammation. This dual activity is particularly relevant in chronic respiratory diseases, where ongoing inflammation and oxidative damage can compromise mucosal integrity. While most research has focused on respiratory mucus, some evidence suggests NAC may also benefit other mucus membranes (e.g., gastrointestinal), though this is less well studied. Overall, the use of NAC for supporting mucus membranes—especially in the respiratory system—is scientifically validated, with a robust body of clinical and mechanistic evidence.