Glycine
Glycine is a simple amino acid and inhibitory neurotransmitter in the brainstem and spinal cord, used as a supplement for sleep quality and calm. Small trials show that a few grams before bed improve subjective sleep and reduce next-day fatigue. It is inexpensive, well tolerated, and carries no dependence risk.
01 Overview
Glycine acts both as an inhibitory neurotransmitter via strychnine-sensitive glycine receptors and as a co-agonist at NMDA receptors. Small placebo-controlled studies report that 3 g before bed improves subjective sleep quality, shortens sleep onset and reduces daytime sleepiness, possibly via a mild drop in core body temperature.
It is also studied at high doses in schizophrenia as an NMDA co-agonist. As a supplement for sleep and calm it has a wide safety margin, with only mild GI effects at higher intakes.
02 Mechanism
Activates inhibitory glycine receptors and acts as an obligatory co-agonist at NMDA receptors; sleep benefits may be mediated by peripheral vasodilation lowering core body temperature.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Sleep quality | 3 g | Oral | 3 g taken about an hour before bed in sleep studies. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Improved subjective sleep qualitySmall placebo-controlled trials show better sleep quality and shorter onset with 3 g before bed. | Mild-moderate | Clinical | |
| Reduced next-day fatigueLess daytime sleepiness and fatigue after glycine-improved sleep. | Mild | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Mild GI upsetNausea or loose stools at higher intakes. | Mild | Uncommon | Observational | |
| Mild drowsinessLight sedation, consistent with its intended sleep use. | Mild | Uncommon | Anecdotal |