Glutathione Before and After in Los Angeles Radiance in 6 Weeks What is glutathione and why must we protect patient access to it? Glutathione 500 mg Plus 21st Century Vitamins 21st Century Vitamins Glutathione is the body's primary internal antioxidant, made using the amino acid cysteine, and it helps protect cells from oxidative stress. Beyond detoxification, research shows glutathione is involved in thyroid hormone metabolism,