Glycine for Sleep

Updated July 14, 2023

Fact-Checked

The Sleep Foundation editorial team is dedicated to providing content that meets the highest standards for accuracy and objectivity. Our editors and medical experts rigorously evaluate every article and guide to ensure the information is factual, up-to-date, and free of bias.

The Sleep Foundation fact-checking guidelines are as follows:

We only cite reputable sources when researching our guides and articles. These include peer-reviewed journals, government reports, academic and medical associations, and interviews with credentialed medical experts and practitioners.
All scientific data and information must be backed up by at least one reputable source. Each guide and article includes a comprehensive bibliography with full citations and links to the original sources.
Some guides and articles feature links to other relevant Sleep Foundation pages. These internal links are intended to improve ease of navigation across the site, and are never used as original sources for scientific data or information.
A member of our medical expert team provides a final review of the content and sources cited for every guide, article, and product review concerning medical- and health-related topics. Inaccurate or unverifiable information will be removed prior to publication.
Plagiarism is never tolerated. Writers and editors caught stealing content or improperly citing sources are immediately terminated, and we will work to rectify the situation with the original publisher(s)
Although Sleep Foundation maintains affiliate partnerships with brands and e-commerce portals, these relationships never have any bearing on our product reviews or recommendations. Read our full Advertising Disclosure for more information.

Up-to-Date

Table of Contents

What is Glycine?
Does Glycine Help Sleep?
How Could Glycine Help Sleep?
Is Glycine Safe?

Glycine is an amino acid that plays a range of important roles throughout the body, including in the immune system, digestion, bones and joints, and the nervous system. It is also sold as a dietary supplement, marketed as a treatment for sleep problems like insomnia.

What is Glycine?

Glycine is one of the main amino acids that form the protein collagen, a component of skin, bones, tendons, and ligaments. It is also involved in the production of proteins that are needed by the immune system and helps make other amino acids, including the genetic material of the body— RNA and DNA Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source .

In the brain, glycine works as a neurotransmitter, affecting how chemical signals are sent in the body. Glycine also plays an important role in breaking down and using fat and fat-soluble vitamins after they are consumed.

Overall, glycine is essential for maintaining body structures, growth, and metabolism. It is commonly found in protein-rich foods such as meat, fish, beans, peas, lentils, and dairy. Most people consume about three to five grams Trusted Source National Center for Biotechnology Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source of glycine per day from food. While small deficiencies of glycine are not dangerous, larger deficiencies may affect a person’s health.

Does Glycine Help Sleep?

As a dietary supplement, glycine is often promoted Trusted Source UpToDate More than 2 million healthcare providers around the world choose UpToDate to help make appropriate care decisions and drive better health outcomes. UpToDate delivers evidence-based clinical decision support that is clear, actionable, and rich with real-world insights. View Source as a cure for insomnia. However, there is not much evidence to back up this claim. Three small human studies suggest that glycine may hold promise as a sleep aid.

In evaluating research studies, experts advise people to consider the size of the study and who conducted and paid for the study, among other things. In the human studies on glycine supplements, the researchers included people who work for a company Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source that manufactures glycine supplements and the number of subjects in the studies was small.

How Could Glycine Help Sleep?

Although it’s not yet clear if glycine supplements help people sleep, scientists have conducted several animal studies to determine how glycine may affect sleep.

Lowers body temperature: In rats, glycine appears to reduce core body temperature. This is important because the body starts to cool off as people fall asleep and body temperature continues to decrease for about two hours after falling asleep. A decrease in core body temperature may also be related to melatonin, a hormone that promotes sleep.
Increases serotonin: Rats that are given glycine also appear to have an increased amount of serotonin in the brain, which researchers believe may help with insomnia Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . Serotonin is a neurotransmitter that is involved in sleep regulation.

Is Glycine Safe?

Glycine, like all dietary supplements, does not undergo the testing that is required for prescription and non-prescription medications. This means that manufacturers do not have to prove that glycine is safe before selling it to consumers.

In human research studies on glycine and sleep, a 3 gram dose of glycine did not cause any side effects Trusted Source Wiley Online Library Wiley Online Library is one of the largest and most authoritative collections of electronic journals published by Wiley, as well as a vast and growing collection of reference works and other books. View Source . Amounts as high as 31 grams Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source and 0.8 grams per kilogram of body weight Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source have been studied for safety. High doses of glycine may cause nausea.

However, it is important to note that excessive amounts of glycine can be toxic, so anyone considering taking a glycine supplement should first check with a health care provider.

Written By

Jay Summer, Staff Writer

Jay Summer is a health content writer and editor. She holds a B.S. in psychology and master's degrees in writing and public policy.

Medically Reviewed by

Dr. Pranshu Adavadkar, Sleep Medicine Physician

As a board-certified sleep medicine physician with over 20 years of clinical experience, Dr. Adavadkar is an expert in diagnosing and treating sleep disorders in both children and adults, as well as addressing sleep issues experienced by veterans. Dr. Adavadkar is a member of the Sleep Foundation Medical Advisory Board.

Learn more about our Editorial Team

References
8 Sources

Razak, M. A., Begum, P. S., Viswanath, B., & Rajagopal, S. (2017). Multifarious Beneficial Effect of Nonessential Amino Acid, Glycine: A Review. Oxidative medicine and cellular longevity, 2017, 1716701.
https://pubmed.ncbi.nlm.nih.gov/28337245/
National Center for Biotechnology Information (2023). PubChem Compound Summary for CID 750, Glycine., Retrieved July 14, 2023 from
https://pubchem.ncbi.nlm.nih.gov/compound/Glycine
Neubauer, D. (2023, May 24). Pharmacotherapy for insomnia in adults. In R. Benca & J. Elmore (Ed.). UpToDate., Retrieved May 30, 2023, from
https://www.uptodate.com/contents/pharmacotherapy-for-insomnia-in-adults
Bannai, M., Kawai, N., Ono, K., Nakahara, K., & Murakami, N. (2012). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology, 3, 61.
https://pubmed.ncbi.nlm.nih.gov/22529837/
Bannai, M., Kawai, N., Nagao, K., Nakano, S., Matsuzawa, D., & Shimizu, E. (2011). Oral administration of glycine increases extracellular serotonin but not dopamine in the prefrontal cortex of rats. Psychiatry and clinical neurosciences, 65(2), 142–149.
https://pubmed.ncbi.nlm.nih.gov/21414089/
Inagawa, K., Hiraoka, T., Kohda, T., Yamadera, W., & Takahashi, M. (2006). Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep and Biological Rhythms, 4(1)
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1479-8425.2006.00193.x
Garlick P. J. (2004). The nature of human hazards associated with excessive intake of amino acids. The Journal of nutrition, 134(6 Suppl), 1633S–1672S.
https://pubmed.ncbi.nlm.nih.gov/15173443/
De Bartolomeis, A., Manchia, M., Marmo, F., Vellucci, L., Iasevoli, F., & Barone, A. (2020). Glycine Signaling in the Framework of Dopamine-Glutamate Interaction and Postsynaptic Density. Implications for Treatment-Resistant Schizophrenia. Frontiers in psychiatry, 11, 369.
https://pubmed.ncbi.nlm.nih.gov/32477178/