By James Myhre & Dennis Sifris, MD 
Updated on May 04, 2022 | Medically reviewed by Lana Butner, ND, LAc

Glycine is an amino acid produced by the body. It is essential in the production of collagen, a protein that gives structure to bones, skin, muscles, and connective tissues. Glycine also plays a role in nerve signal transmission and clearing toxins from the body.

Unlike some amino acids that must be obtained solely through foods, the body can produce glycine. It is also available in supplement form.

Some research indicates supplemental glycine may benefit insomnia, stroke recovery, and even certain psychiatric disorders. However, the evidence is limited, so further studies are needed.

This article looks at glycine supplements' potential benefits and risks and whether the current science supports the health claims. It also offers tips on how to select and use glycine supplements safely.

 

Uses of Glycine

Glycine use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or doctor. No supplement is intended to treat, cure, or prevent disease. 

Glycine is an amino acid that serves as a building block for specific proteins, including collagen, a structural protein found in connective tissues. Collagen is found in:

  • Skin
  • Ligaments
  • Muscles
  • Bones
  • Cartilage

Glycine also helps regulate nerve impulses in the central nervous system. This system affects the spinal cord and the brain. Glycine also binds to toxins so that the body can clear them.

In addition to the glycine already produced by the body, you can also take glycine supplements. Most current research has focused on glycine's role in sleep, mood, stroke, and heart disease.

Mood and Memory

Glycine stimulates the production of serotonin, the "feel-good" hormone that helps elevate mood, improve sleep, and enhance memory and thinking.

Studies on rodents have demonstrated that glycine supplementation increases serotonin levels.2 Due to these effects, some people tout glycine supplements as "natural antidepressants." However, their impact on the brain appears to be short-lived, often dissipating within minutes.

For example, in a 2011 study in Psychiatry and Clinical Neurosciences, researchers measured serotonin levels in rats after glycine administration. They found that serotonin increased for only 10-20 minutes after glycine supplementation compared to more than 180 minutes after receiving a selective serotonin reuptake inhibitor (SSRI), an antidepressant medication.3

 

Sleep

Some research suggests that glycine supplements may improve sleep in people with insomnia. For example, a 2015 study from Japan evaluated why sleep improved in rats after glycine supplementation.4 To assess the effects, researchers implanted a telemetry unit on the animals. After recovery, rats were given either glycine or water.

Those who received glycine had significantly decreased wakefulness and increased non-rapid-eye-movement (NREM) sleep during the first 90 minutes compared with the control group. Researchers concluded that glycine promotes sleep because it alters body temperature and circadian rhythms.4

Again, scientists did this research on animals, and therefore it is uncertain whether these results would translate to humans.

In a 2012 human study, researchers evaluated glycine's effects on daytime performance in sleep-restricted participants.5 In the randomized single-blinded crossover trial, seven healthy adults without sleep disorders had their time in bed reduced by 25% for three nights. They were then given 3 grams of glycine or a placebo 30 minutes before bed.

Participants rated their daytime sleepiness, fatigue, and performance. Glycine significantly improved fatigue feelings, reduced sleepiness, and improved performance compared to the placebo group.