What Is N-Acetyl L-Cysteine? N-Acetyl L-Cysteine, also called acetylcysteine, is derived from the amino acid, L-Cysteine, and is a source of Cysteine for the body. NOW available in capsules! All the great benefits of NAC made easy! N-Acetyl L-Cysteine Benefits † Experience fast-acting, full-body relaxation with this do-it-all supplement. N-Acetyl L-Cysteine is a non-essential amino acid used for detoxification. N-Acetyl L-Cysteine has a wide range of health benefits and may assist in the production of antioxidants. NAC may support the kidneys, liver, and lungs and promote healthy immune function. It may also contribute to healthy skin and support sexual health and brain function, as well as promote a healthy mood. Source of the amino acid Cysteine Detoxify to support and protect kidneys and liver Essential for making the powerful antioxidant Glutathione Promote healthy mood Support healthy brain function Contribute to sexual health Promote healthy skin Provide support for the lungs Support fertility