Another beneficial source is whey protein because its rich in cysteine
A Cochrane systematic review of NAC for COPD exacerbations (39 RCTs, n=7,436) found that NAC and other mucolytics significantly reduced the frequency of acute exacerbations (OR 0.75, 95% CI 0.62-0.92) (Poole et al., Cochrane Database Syst Rev, 2019) [43]
In this review, we emphasize on (1) GSH depletion as a fundamental risk factor for diseases like chronic obstructive pulmonary disease and atherosclerosis (ischemic heart disease and stroke), (2) importance of oxidative stress and antioxidants in SARS-CoV-2 infection and COVID-19 disease, (3) significance of GSH to counteract persistent damaging inflammation, inflammaging and early (premature) inflammaging associated with cell and tissue damage caused by excessive oxidative stress and lack of adequate antioxidant defenses in younger individuals, and (4) new therapies that include antioxidant defenses restoration
They indicate that identity, manufacture, impurity control, aggregation, formulation, route, and exposure cannot be assumed safe from the peptide name or an HPLC purity value alone