N-acetyl-l-cysteine (nac) is a more stable form of the amino acid l-cysteine and is the most effective way to boost glutathione levels in the body. Nac has all the properties of l-cysteine but is more water soluble and said to be more bio-available than l-cysteine. Nac naturally stimulates glutathione, an antioxidant enzyme. People who have autoimmune problems are often deficient in glutathione. Nac has been used to raise immunity to the flu and also to treat chronic respiratory problems. Nac makes up glutathione, a critical antioxidant scientifically proven to scavenge free radicals. Nac has the unique ability to maintain healthy lung tissue, support the body's natural defences and enhance cellular health and longevity. These qualities make nac especially beneficial for active people, the elderly and those exposed to polluted environments.