How many studies support Glycine?

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. That's backed by 8 published studies in Vitaebase's database, including 1 randomized controlled trial, the most recent from 2023 -- a fairly substantial body of research for a single topic.