Does NAC improve lung health, mental health or recovery, and which benefits have convincing human evidence?

N-acetylcysteine, or NAC, supplies a precursor used to make glutathione and can help loosen mucus. Its respiratory evidence is about defined illnesses, not making healthy lungs “cleaner.” In the PANTHEON randomized trial, a year of oral NAC reduced exacerbations in Chinese patients with moderate-to-severe COPD compared with placebo. That is a clinically relevant outcome, but it does not show that every person with breathlessness, a cough or normal lungs benefits. The population, existing respiratory treatment and reason for using it matter.[1]

Mental-health findings are more uncertain. A randomized trial of NAC added to treatment for major depression did not show a significant advantage on its primary depression outcome, although some secondary and later findings were encouraging. That is different from proving a reliable antidepressant effect. Likewise, changing antioxidant measures is not the same as improving training recovery, strength or day-to-day energy. The cited respiratory and psychiatric trials do not establish those fitness benefits. NAC is best evaluated against a specific problem and measurable outcome, rather than the broad promise of reducing all oxidative stress.[1][2]