Does Glycine actually make a difference, or is it overhyped?

The most established use of glycine alone is sleep: real controlled studies and reviews find glycine taken before bed improves subjective sleep quality and reduces daytime sleepiness after partial sleep restriction, though the evidence base for this specific effect is relatively small. Weighing the data: Glycine looks an early-stage, lower-priority area for now — the evidence is only emerging (18/100), and its estimated impact (15/100) is on the lower end too.