Glycine vs L-Theanine
for sleep
Stronger evidence: tie
Stronger effect: tie
Safety: L-Theanine carries a minor interaction; Glycine has none recorded.
For sleep, the two are evidence-matched; the difference is in effect and safety.
Glycine
grade C low certainty
small trials suggest improved subjective sleep quality and reduced next-day fatigue
3 g before bed, adults
L-Theanine
grade C low certainty
may improve subjective sleep quality via relaxation rather than sedation
200 mg before bed, adults
sources: PMID:10000002 · PMID:42180808