Our ancestors ate whole animals. Skin, cartilage, tendons, bones, organs. That meant they consumed massive amounts of glycine from collagen rich tissues. Modern humans eat almost exclusively muscle meat, which is extremely high GSH exists as a tri amino acid combination of glycine, cysteine, and Download Scientific Diagram The Anti Aging and Longevity Benefits of Glycine Glycine and N acetylcysteine (NAC) are amino acidbased nutrients that serve as precursors for glutathione, one of the body's most important intracellular antioxidants. Glutathione plays a central role in reducing oxidative stress, supporting Prion protein regulates glutathione metabolism and neural glutamate and cysteine uptake via excitatory amino acid transporter 3 Guitart 2015 Journal of Neurochemistry Wiley Online Library Frontiers Glutathione: A Samsonian life sustaining small molecule that protects against oxidative stress, ageing and damaging inflammation