Glycine
What it is
Inhibitory amino-acid neurotransmitter that lowers core body temperature (via NMDA receptors in the suprachiasmatic nucleus), promoting sleep onset.
What the evidence says
Promising but limited to small trials, mostly from one research group (Ajinomoto). In sleep-restricted healthy volunteers, 3 g glycine before bed improved subjective daytime fatigue and performance. An earlier polysomnography study (Yamadera 2007) found 3 g shortened latency to sleep onset and slow-wave sleep and improved subjective sleep quality. Samples are tiny (often <20), short, and lack independent replication, so confidence is moderate-to-low.
3 g taken ~30-60 minutes before bedtime.
Educational summary of doses studied — not a recommendation. Talk to a clinician before starting any supplement.
Sources (2)
- The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers (PMID: 22529837) — Frontiers in Neurology (2012)
- Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes — Sleep and Biological Rhythms (2007)
Educational summary of published research, checked against primary sources and linked inline. Not medical advice; supplements are not FDA-evaluated to treat disease. See our editorial policy.