- There are research reports that glycine has a beneficial effect on sleep quality and sleep-onset time.
- The evidence score is 9 for sleep quality and 5 for sleep-onset time, but the reliability is very limited for both.
- This information is intended for people looking into sleep quality or the time it takes to fall asleep.
Glycine is a type of amino acid.
It is a substance present in the body and is generally consumed as a nutritional component.
Studies have reported that glycine has a beneficial effect on sleep quality.
2 studies address this point.
First, in a study of humans, it was reported that taking glycine before bed significantly (in a way that is statistically meaningful, not simply attributable to chance) improved subjective sleep quality (based on how one feels oneself).
In addition, a study using rats suggests that a mechanism in the brain may be involved. Specifically, there is a report that glycine acts to promote sleep via NMDA receptors in the brain (a kind of window through which signals in the brain are received).
These suggest a possible ability to support sleep quality, but this is still at the research stage, and whether the same occurs in humans remains open to examination.
One study has also been reported on a beneficial effect for the time it takes to fall asleep.
This study targeted rats.
The results of the study showed that the time to transition into NREM sleep (non-REM sleep: sleep in which the brain is in a resting state) was shortened. It was also reported that core body temperature (the temperature inside the body) decreased.
This study is based on an animal study (research conducted on animals). Therefore, whether the same can be said for humans is a matter that requires further research at this stage.
Looking at the evidence score (an indicator showing the strength of the basis based on the quality and quantity of research), the score is 9 for sleep quality and 5 for sleep-onset time.
These numbers reflect an evaluation of the accumulated research and its content.
However, both figures have been rated as very limited in reliability (a state in which study results are still few and cannot be considered certain). There are several reasons for this.
One is that the number of studies is still small. Another reason the reliability is rated as very limited is that the research includes animal experiments using rats rather than humans.
Some people will not experience an effect from these findings. It may also not suit some people depending on their constitution. Please note that the data presented here is simply content reported as research and does not guarantee that it applies to everyone.
| Study | Design | Number of Participants | Duration | Main Result |
|---|---|---|---|---|
| Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology (2015, PMID:25533534) | Animal study | Unknown | Unknown | A beneficial effect was reported |
| Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology (2015, PMID:25533534) | Animal study | Unknown | Unknown | A beneficial effect was reported |
| Advances in Biochemical Engineering/Biotechnology (2017, PMID:27872968) | Other study design | Unknown | Unknown | A beneficial effect was reported |
Rats were used as the subjects of the research.
Since this is a study conducted on animals, it can serve as a reference when considering whether it applies to you.
The number of studies is 3, and the reported content is very limited.
The study designs include animal experiments, and there are also reports using other formats.
It should be noted that this has not reached the stage of establishing definitive results in humans.
Is glycine related to falling asleep?
In a study using rats, there is a report of a beneficial effect on the time it takes to fall asleep. A decrease in core body temperature was also reported at the same time.
Does glycine affect sleep quality?
2 studies have reported a beneficial effect on sleep quality. These studies are based on very limited reliability.
When is the best time to take glycine?
There is a research report that taking it before bed improved subjective sleep quality. This is based on a 2017 study.
Studies have reported that glycine may have a beneficial effect on sleep quality and the time it takes to fall asleep. However, since the number of studies is small and includes animal experiments, the reliability is very limited. Please use the research findings simply as one indicator, adapted to your own situation.
Why not try the self-check assessment to objectively understand the state of your own sleep?