Natural Factors N-Acetyl-L-Cysteine - 1000 mg - NAC is a free form amino acid and a powerful antioxidant that has shown itself to be an effective detoxifier and a natural strengthener of the immune system. A precursor to glutathione, a key antioxidant that fights oxidative stress, maintains a healthy immune system, repairs tissues and supports overall health. Supplementing with NAC is a more reliable way to increase glutathione levels than supplementing directly with glutathione, which breaks down in the digestive tract. NAC 1000 mg is especially beneficial for active people, older adults, and people who live or work in polluted environments.