Your body can synthesise a lot of things, which is why they are often considered non essential, glycine being one of them. Here's a study, not read this one be

Your body can synthesise a lot of things, which is why they are often considered non essential, glycine being one of them. Here's a study, not read this one before, but its not hard to find https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115565/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115565/ "The pineal hormone melatonin was also measured in the present and previous study (11), with significantly increased plasma concentrations being observed during sleep deprivation. Increased tryptophan and taurine could explain the increased melatonin levels, as taurine has been shown to increase pineal melatonin by stimulating the activity of its rate limiting biosynthetic enzyme, N-acetyltransferase (42). "