Glycine is a small amino acid found in protein foods and sold as a supplement. It has gained attention for sleep because it may help lower core body temperature, support sleep quality, and improve next-day alertness in some studies.
How Glycine May Help Sleep
Sleep onset requires a drop in core body temperature. Glycine may support that process by promoting peripheral blood flow, helping the body release heat. This is one reason some people feel sleepier after taking it before bed.
What the Research Suggests
Small human studies suggest that glycine before bed may improve subjective sleep quality and reduce next-day fatigue. The evidence is not massive, but it is interesting because glycine appears to support natural sleep processes rather than acting like a sedative.
Dosage and Timing
A commonly studied dose is around 3 grams before bed. It is often mixed into water because glycine tastes slightly sweet. Start lower if you are sensitive to supplements or prone to digestive upset.
Possible Side Effects
- Nausea or stomach discomfort
- Soft stools in some people
- Unwanted sleepiness if combined with other calming substances
Who Might Benefit Most?
- People who run warm at night
- People with light sleep but no obvious sleep disorder
- People trying to improve sleep quality without melatonin
- People who already have consistent sleep timing but want better recovery
If your bedroom is warm, fix temperature first. See our guide to the best bedroom temperature for sleep.