Key Takeaways
- Glycine is an amino acid naturally produced by the body and obtained through food.
- It functions as a neurotransmitter and is involved in communication within the central nervous system.
- Researchers have investigated glycine in relation to sleep quality, sleep physiology and body temperature.
↓ Jump to
📖 5 min readGlycine occurs naturally in protein-rich foods, particularly foods containing collagen and connective tissue. When it comes to sleep, most of us think about our bedtime routine, caffeine intake, screen time and bedroom environment. But researchers are also interested in the biological processes that help regulate how and when we sleep.
One nutrient being studied in this area is glycine. Glycine is a naturally occurring amino acid found throughout the body and in many protein-rich foods. It has several established physiological roles, including contributing to protein and collagen synthesis and functioning as a neurotransmitter within the central nervous system (R).
Researchers have also investigated the relationship between glycine and sleep. While the evidence is still developing, early studies offer an interesting look at how this everyday amino acid may interact with some of the processes involved in sleep.
What Is Glycine?
Glycine is the smallest amino acid and one of the building blocks the body uses to make proteins. Unlike essential amino acids, which must be obtained through food, glycine can be produced by the body. It is therefore generally classified as a non-essential amino acid.
Glycine is also obtained through the diet and is found in a variety of protein-rich foods. Beyond its role in proteins, glycine participates in numerous biochemical processes. It is involved in collagen synthesis and the production of compounds including glutathione, creatine and haem. It also has an important role within the nervous system (R). It is this neurological role that has led researchers to investigate glycine in relation to sleep.
Glycine at a Glance
Glycine is a naturally occurring amino acid used throughout the body. It contributes to protein and collagen formation and also plays a role in communication within the nervous system.
What Does Glycine Do in the Nervous System?
Glycine functions as a neurotransmitter — a chemical messenger used by nerve cells to communicate. Within parts of the central nervous system, glycine acts as an inhibitory neurotransmitter, helping regulate signalling between nerve cells. Glycine also interacts with NMDA receptors, which are involved in a range of neurological processes (R).
Because sleep is regulated through a complex interaction between the brain, nervous system, hormones, circadian rhythms and environmental cues, researchers have investigated whether glycine may influence some of these processes.
What Does the Research Say About Glycine and Sleep?
A small number of human studies have examined supplemental glycine in relation to sleep. Some have reported changes in subjective measures, such as sleep quality and next-day fatigue, while researchers have also investigated possible effects on aspects of sleep physiology (R).
The human research conducted to date is relatively limited, with several studies involving small numbers of participants. The existing research should not be taken to mean that consuming glycine will necessarily improve sleep. Instead, it provides an emerging area of research into how glycine may interact with the physiological processes associated with sleep.
What the Evidence Tells Us So Far
Early human research has explored glycine in relation to sleep quality, next-day fatigue and sleep physiology. However, the evidence remains limited, and larger studies are needed before firm conclusions can be drawn.
Glycine, Body Temperature and Sleep
One particularly interesting area of research concerns core body temperature. Body temperature follows a natural daily rhythm. As bedtime approaches, core body temperature typically begins to fall as part of the body’s preparation for sleep.
Researchers have investigated whether glycine may influence mechanisms involved in thermoregulation and whether this could help explain some observations from sleep studies (R). This is one proposed mechanism being explored, not proof that glycine will improve sleep. It also illustrates an important point: sleep isn’t controlled by a single nutrient or biological pathway. It emerges from multiple systems working together.
Why Body Temperature Matters
Core body temperature naturally changes across the day and generally begins to decline as bedtime approaches. Researchers are investigating whether glycine interacts with processes involved in this thermoregulatory response.
Can You Get Glycine From Food?
Yes. Glycine occurs naturally in many protein-containing foods. It is particularly abundant in collagen, where glycine makes up approximately one-third of the amino acids in the collagen structure (R). Dietary sources of glycine include:
- meat and poultry
- fish and seafood
- skin-on poultry and fish
- slow-cooked cuts containing connective tissue
- gelatin
- collagen-containing foods
- eggs
- dairy products
- legumes
Eating a varied diet with adequate protein provides glycine, along with the many other amino acids and nutrients the body requires.
Food Sources of Glycine
Glycine occurs naturally in many protein-rich foods and is especially abundant in collagen and connective tissue. A varied diet containing adequate protein can contribute glycine alongside other important amino acids and nutrients.
Glycine Is Only One Part of the Sleep Picture
It’s easy to become interested in individual nutrients when emerging research appears promising. But sleep is influenced by far more than any single dietary component.
Regular sleep and wake times, light exposure, physical activity, caffeine and alcohol intake, stress, bedroom environment and overall dietary patterns can all influence sleep. Individual sleep requirements also vary. For this reason, glycine is best understood as one area of ongoing sleep research, rather than a standalone solution for better sleep.
Sleep Is Multifactorial
No single nutrient determines how well you sleep. Sleep is influenced by factors including circadian rhythms, light exposure, physical activity, stress, caffeine, alcohol, diet and your sleep environment.
Why Researchers Are Interested in Glycine
Glycine is already known to have numerous physiological roles throughout the body. Its activity within the nervous system, together with early observations from sleep research, has prompted scientists to continue investigating its potential relationship with sleep physiology.
There are still important questions to answer, including which mechanisms are most relevant, whether findings are reproducible in larger populations and how factors such as dose and individual differences affect outcomes. Larger and more robust human studies will help provide a clearer picture.
The Bottom Line
Glycine is a naturally occurring amino acid with established roles in protein synthesis, collagen formation and nervous system signalling. Researchers have also investigated glycine in relation to sleep, including possible relationships with sleep quality, sleep physiology and thermoregulation.
While some early human studies have reported interesting findings, the evidence remains limited and further research is needed before firm conclusions can be drawn about glycine intake and sleep outcomes.
This article is for general educational purposes and is not intended to diagnose, treat, cure or prevent any medical condition. If you have persistent sleep difficulties or concerns about your health, speak with an appropriately qualified healthcare professional.
Interested in learning more about how to support healthy sleep? Read our related blog: 5 Proven Ways to Fix Broken Sleep.
