Glycine and sleep
3 g before bed improved subjective sleep in small Japanese trials funded in part by a glycine maker.
Education only, not medical advice. Talk to your clinician before starting a supplement, especially if you are pregnant, take medication or have a condition.
Evidence grade: C (A strong, B good with gaps, C limited or mixed, D early)
The trials
In a small crossover study, 3 g of glycine before bed improved subjective sleep quality and shortened time to deep sleep on polysomnography [1]. In partially sleep-restricted volunteers it reduced next-day fatigue [2]. Rodent work suggests it lowers core body temperature through receptors in the brain's clock [3].
Critique
These studies were small, short and conducted by researchers affiliated with a glycine manufacturer [1][2]. We grade the evidence C.
Sources
- Yamadera et al. 2007, Sleep Biol Rhythms. doi.org/10.1111/j.1479-8425.2007.00262.x
- Bannai et al. 2012, Front Neurol. doi.org/10.3389/fneur.2012.00061
- Kawai et al. 2015, Neuropsychopharmacology. doi.org/10.1038/npp.2014.326
DOIs verified against Crossref and official pages checked on 2026-10-15.