N-acetylcysteine
N-acetylcysteine is a precursor of an amino acid (L-cysteine), which is itself a component of an antioxidant. It may help protect against oxidative stress by maintaining or increasing antioxidant levels in the body. Some clinical trials testing formulations that included N-acetylcysteine have found modest improvements in cognitive function, but clinical trials testing it alone have shown less robust results. N-acetylcysteine supplements are generally regarded as safe when taken at recommended doses.