GlyNAC (Glycine + N-acetylcysteine)

GlyNAC is the combined oral supplementation of glycine and N-acetylcysteine (NAC), designed to replenish both precursors of the tripeptide glutathione (γ-Glu-Cys-Gly), which declines progressively with age. The combination addresses the limiting precursors simultaneously — cysteine (via NAC) and glycine — rather than the gamma-glutamylcysteine step, which is typically less rate-limiting in older adults. Pioneered by Rajagopal Sekhar and colleagues at Baylor College of Medicine, a series of randomized, double-blind pilot trials in older adults (GlyNAC trials, published 2021–2024, with n≈8–24 per arm) using 16–24 weeks of supplementation reported restoration of erythrocyte glutathione toward young-adult levels and signals across multiple aging-associated domains (mitochondrial fuel oxidation, oxidative stress, inflammation, endothelial dysfunction, insulin resistance, genomic damage, muscle strength, gait speed). Independent replication and longer outcome trials are lacking. Evidence remains limited to short-duration trials with small samples; longer-term RCTs with clinical outcome endpoints are lacking. GlyNAC is commercially available as a dietary supplement and has no approved indication.