Glycine vs 5-HTP

for sleep

Stronger evidence: tie

Stronger effect: Glycine

Safety: 5-HTP carries a serious interaction; Glycine has none recorded.

For sleep, the two are evidence-matched; the difference is in effect and safety.

grade C low certainty

small trials suggest improved subjective sleep quality and reduced next-day fatigue

3 g before bed, adults

grade C low certainty

limited evidence for sleep; serotonergic, so caution with antidepressants

sources: PMID:10000002 · PMID:00000036