Most sleep supplements have weak or conflicting evidence. Glycine shows modest benefit with an excellent safety profile. Magnesium is mechanistically plausible but underwhelming in trials. Ashwagandha shows a small but real signal at ≥600 mg/day for ≥8 weeks, but quality control is abysmal — only 5 of 13 tested brands were accurate. Phosphatidylserine has mixed evidence but Peter Attia uses it personally for jet lag.