Glycine: A Key To Better Sleep, Mood, and Overall Health

Glycine: A Key To Better Sleep, Mood, and Overall Health

Glycine is an amino acid that plays numerous roles throughout the body. It is a protein building block and a neurotransmitter, facilitating communication between neurons and cells.

This allows glycine to have a wide-ranging influence on health, from brain function to metabolism. Most notably, glycine impacts sleep quality. 

In this article, we examine the research on glycine in humans and animals to explore its potential health effects. From sleep to cognition and blood sugar control, glycine has the potential to improve physical and mental health. 


What is Glycine?

Glycine is an amino acid (a building block of protein). It’s considered “conditionally” essential, meaning the body can typically produce glycine in sufficient quantities. However, during certain life phases, such as pregnancy, the body may not produce enough glycine, which should be consumed through foods and supplements. Many protein-rich foods contain glycine. Animal sources like meat, dairy, and eggs, as well as plant-based foods like soy and lentils, contain this amino acid [1].

So, why is glycine a stand-out amino acid? In addition to its role as an amino acid, glycine is also a neurotransmitter. It sends chemical messengers to help facilitate communication between neurons and cells. This has sparked numerous studies to better understand glycine’s ability to impact the brain and associated processes. Most notably, glycine has been shown to impact sleep quality. It may also have other cognitive benefits, too [1].


How Does Glycine Work?

Glycine plays a crucial role in improving sleep quality through its interaction with the brain's N-methyl-D-aspartate (NMDA) receptors. As an inhibitory neurotransmitter, glycine acts as a co-agonist at NMDA receptors, modulating their activity [2].

This interaction is particularly important in the regulation of sleep-wake cycles. By binding to NMDA receptors, glycine reduces core body temperature and increases peripheral blood flow, two physiological changes associated with sleep onset. As the body is preparing for rest, its temperature drops by a couple of degrees, promoting relaxation and sleepiness [3]. 

Glycine's action on NMDA receptors in the suprachiasmatic nucleus, the brain's central circadian clock, helps to synchronize sleep patterns. This mechanism contributes to glycine's ability to reduce sleep onset time, improve sleep efficiency, and enhance overall sleep quality, making it a promising supplement for those seeking better rest [4, 5, 6]. 

NMDA also plays a role in synaptic plasticity, meaning it can help to influence brain functions, including memory formation [7]. 


Glycine is Well-Studied to Impact Sleep

Glycine has garnered significant research attention due to its potential to improve sleep. Here, we discuss the scientific evidence supporting glycine's role in enhancing sleep quality, specifically sleep efficiency, deep sleep, sleep latency, and subjective sleep quality. 

 

Improved Sleep Efficiency

Research suggests that glycine supplementation can significantly improve sleep efficiency. A study found that consuming 3 grams of glycine one hour before bedtime led to measurable improvements in sleep quality. 

Researchers hypothesize that the enhancement in sleep efficiency is due to glycine's ability to influence sleep-related physiological processes like lowering core body temperature and modulating NMDA. These effects contribute to easier sleep onset, ultimately improving overall sleep efficiency [8, 9]. 

 

Enhanced Deep sleep

Glycine supplementation has been shown to enhance deep sleep. A study demonstrated that taking 3 grams of glycine before bedtime improves objective sleep quality, including slow-wave sleep (also known as deep sleep), in those who are not sleeping well. 

Glycine intake improved deep sleep without altering sleep architecture (the natural progression of sleep stages) [10]. 

 

Reduced Sleep Latency

Glycine has also been shown to improve sleep latency (the time it takes to fall asleep). An animal study (conducted in rats) found that it significantly improved sleep latency in rats experiencing acute sleep disturbance.

This effect was accompanied by a simultaneous decrease in rats’ core body temperature, a physiological change associated with sleep onset [3]. 

 

Improved Subjective Sleep Quality

Glycine supplementation has also been shown to improve subjective sleep quality measures, including fatigue and alertness. One study investigated the impact of glycine supplementation in 10 partially sleep-restricted adults (sleeping 25% less than their baseline total sleep, an average of 5.5 hours/night for three nights). They found that despite getting less sleep, taking a glycine supplement was associated with less daytime fatigue and better perceived alertness [9, 11]. 

Another study found that taking a 3g glycine supplement an hour before bed helped to improve subjective fatigue, liveliness and peppiness, and clear-headedness, compared to a placebo group [12].  

A literature review found that glycine significantly improved fatigue the next morning, indicating that glycine helps improve sleep quality in humans [13]. 


Health Benefits of Glycine Supplementation

While glycine is primarily known to improve sleep quality, it is also associated with health benefits that extend beyond better rest. Human and animal studies show that glycine can positively impact aspects of both physical and mental health. 

Here, we unpack the growing body of evidence supporting glycine's benefits on memory and mood, cardiovascular health, inflammation, and blood sugar control. We’ll also explore animal research showing that glycine supplementation may even extend lifespan. 


Glycine May Improve Mood, Memory, and Cognition

Glycine supplementation has been shown to improve performance on memory recognition tasks. This study investigated the effects of taking 3g of glycine before bedtime on both sleep and cognitive performance. They found that glycine intake enhanced performance on memory recognition tasks. The researchers conclude that glycine's sleep-improving effects differ from traditional drugs like benzodiazepines, suggesting an alternative for improving sleep quality and daytime cognitive function [8]. 

Glycine has also been shown to maintain healthy cognition in both young and middle-aged people.​​ A study examined the effects of Bioglycin, a biologically active form of glycine, on cognitive function in healthy young students and middle-aged men. Using a double-blind, randomized, crossover design, researchers found that Bioglycin significantly improved episodic memory retrieval in both age groups. While it didn't affect focused or divided attention, middle-aged participants showed improved sustained attention. Glycine may be beneficial in scenarios requiring high information retrieval or when factors like jet lag or disrupted sleep impair performance [14].  

A study in mice investigated the effects of different glycine doses on mood hormones. Significant changes in glycine concentration were observed, affecting the NMDA neurotransmitter. They also found significant increases in serotonin metabolites and dopamine, known as the "feel-good hormones" [15].


Blood Sugar Control and Type 2 Diabetes Risk Are Improved When Glycine Levels are Sufficient 

Glycine supplementation has also been studied to impact metabolic health, including blood sugar markers like glucose and hemoglobin A1c and type 2 diabetes risk. 

A systematic review and meta-analysis of 8 prospective studies found that higher glycine and glutamine levels were associated with a lower risk of type 2 diabetes (while other amino acid concentrations were associated with an increased risk) [16]. 

Another study examined the effects of taking 5g of glycine per day on 74 type 2 diabetes patients. After three months, glycine significantly lowered hemoglobin A1c levels (a long-term blood sugar measure) and proinflammatory cytokines while increasing IFN-γ. The findings suggest glycine supports a healthy anti-inflammatory status and promotes proper glucose metabolism [17]. 

Yet another study also found that glycine supports healthy glucose responses, improving it by over 50%. The results suggest oral glycine may stimulate a gut hormone that enhances insulin's effect on glucose removal [18].  


Glycine Supplements May Reduce Frequent Nighttime Urination (Nocturia)

Glycine supplementation may help to reduce frequent nighttime urination in those with an overactive bladder. A study examined the effects of dietary glycine on storage symptoms in 20 urological participants with overactive bladder. Compared to placebo, glycine significantly improved various urinary symptoms, including reduced nocturnal voids, urgency, and overall storage symptoms. Fewer urinary symptoms in the night meant participants were also able to improve their sleep quality and quality of life [19].


Optimal Glycine Levels May Be Cardioprotective

Glycine has also been shown to be cardioprotective (associated with better heart health). A study investigated the association between plasma glycine levels and the risk of acute myocardial infarction (AMI) in 4,109 participants. Over a median follow-up of 7.4 years, higher plasma glycine levels were associated with a more favorable lipid profile and lower prevalence of obesity, hypertension, and diabetes mellitus (common AMI risk factors). After adjusting for traditional coronary heart disease risk factors, higher plasma glycine levels were inversely associated with AMI risk. This association was stronger in patients with elevated ApoB, LDL cholesterol, or ApoA-1 levels. The findings suggest a potential cardioprotective effect of glycine. Further research is warranted to understand the benefits of glycine on heart health [20].  


Glycine is Anti-Inflammatory and Increases Antioxidant Status

As mentioned in metabolic studies, glycine supplementation supported a better inflammatory status [17].

Glycine is also a building block of glutathione, the “master antioxidant” in the body. This antioxidant helps to build and repair tissues and reduce inflammation. Glutathione levels tend to decrease with age, increasing oxidative stress. Studies show that supplementing with glycine can help to improve glutathione status in those that have low levels [21]. 


Muscle and Joint Health

As an amino acid, glycine supports joint and bone health. Studies show that glycine is associated with a reduced risk of osteoporosis (the loss of bone mineral density). Osteoporosis often accompanies aging and puts individuals at a higher risk of fatal falls and fractures [22]. 

Glycine plays a critical role in skeletal muscle mass and has been shown to protect muscle breakdown in high-stress conditions [23].


Glycine Has Extended Lifespan in Animal Models

Animal studies conducted in three different animal models show that glycine can extend lifespan. One study found that glycine supplementation extended the median lifespan of rats by 28%, and the maximum lifespan increased by 31% compared to a control group [24]. 

Another study conducted in Drosophila found that improving glycine metabolism extended lifespan [25]. 

Glycine appears to play a role in decelerating aging through the methionine cycle — a 19% increase in lifespan was observed in C. elegans [26].  


Are There Side Effects of Taking Glycine Supplements?

Glycine supplements are generally safe, with minimal or no adverse events reported after taking the supplement. Oftentimes, sleep-promoting supplements can leave you feeling groggy the next morning. Glycine, in dosages up to 9g, did not result in daytime sleepiness [27]. In fact, multiple studies showed that taking glycine helped reduce feelings of fatigue the next morning [9, 11, 12, 13]. 

If you are new to glycine supplementation, consider working your way up to a full dosage. Too much, too fast may lead to gastrointestinal (GI) upset [27]. 


How and When to Take a Glycine Supplement

Before taking a glycine supplement, it's helpful to understand proper dosage and timing. Glycine supplement dosages in the aforementioned studies range from 3g to 5g and are safe up to 9g. 

For optimal results, glycine is usually taken within one hour of bedtime, as it's primarily used to promote better sleep quality. It's worth noting that glycine is frequently included as an ingredient in sleep supplements, often combined with other calming and sleep-enhancing compounds such as magnesium and L-theanine. This approach may provide synergistic benefits for those seeking to improve their sleep.


Key Takeaways

  • Glycine is an amino acid (a building block of protein) and a neurotransmitter (meaning it helps to facilitate communication between neurons and cells).
  • Research shows that glycine can significantly improve sleep quality, efficiency, and latency, as well as subjective sleep measures.
  • Glycine may also enhance cognitive function, including memory and mood.
  • Glycine may aid in blood sugar control and reduce type 2 diabetes risk. It is also anti-inflammatory and a precursor to antioxidants.
  • Glycine supports cardiovascular, muscle, and joint health and potentially even lifespan.
  • Glycine supplements are generally safe with minimal side effects, including GI symptoms.
  • Optimal dosage ranges from 3-5g, taken about an hour before bedtime. 

References

  1. Aguayo-Cerón, K. A., Sánchez-Muñoz, F., Gutierrez-Rojas, R. A., Acevedo-Villavicencio, L. N., Flores-Zarate, A. V., Huang, F., Giacoman-Martinez, A., Villafaña, S., & Romero-Nava, R. (2023). Glycine: the smallest Anti-Inflammatory micronutrient. International Journal of Molecular Sciences, 24(14), 11236. https://doi.org/10.3390/ijms241411236 
  2. Johnson, J. W., & Ascher, P. (1987). Glycine potentiates the NMDA response in cultured mouse brain neurons. Nature, 325(6104), 529–531. https://doi.org/10.1038/325529a0 
  3. Kawai, N., Sakai, N., Okuro, M., Karakawa, S., Tsuneyoshi, Y., Kawasaki, N., Takeda, T., Bannai, M., & Nishino, S. (2014). The Sleep-Promoting and Hypothermic Effects of Glycine are Mediated by NMDA Receptors in the Suprachiasmatic Nucleus. Neuropsychopharmacology, 40(6), 1405–1416. https://doi.org/10.1038/npp.2014.326 
  4. Mordel, J., Karnas, D., Inyushkin, A., Challet, E., Pévet, P., & Meissl, H. (2011). Activation of glycine receptor phase‐shifts the circadian rhythm in neuronal activity in the mouse suprachiasmatic nucleus. The Journal of Physiology, 589(9), 2287–2300. https://doi.org/10.1113/jphysiol.2010.204693 
  5. Acosta-Rodríguez, V. A., Rijo-Ferreira, F., Green, C. B., & Takahashi, J. S. (2021). Importance of circadian timing for aging and longevity. Nature Communications, 12(1). https://doi.org/10.1038/s41467-021-22922-6 
  6. Circadian release of amino acids in the suprachiasmatic nucleus in vitro (1998). NeuroReport. https://journals.lww.com/neuroreport/abstract/1998/01050/circadian_release_of_amino_acids_in_the.27.aspx 
  7. Jewett, B.E.; Thapa, B. (2022). Physiology, NMDA Receptor. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK519495/ 
  8. Yamadera, W., Inagawa, K., Chiba, S., Bannai, M., Takahashi, M., & Nakayama, K. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms, 5(2), 126–131. https://doi.org/10.1111/j.1479-8425.2007.00262.x 
  9. Potter, G. D. M., & Wood, T. R. (2020). The future of shift work: Circadian Biology meets personalised medicine and behavioural science. Frontiers in Nutrition, 7. https://doi.org/10.3389/fnut.2020.00116 
  10. Yamadera, W., Inagawa, K., Chiba, S., Bannai, M., Takahashi, M., & Nakayama, K. (2007b). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms, 5(2), 126–131. https://doi.org/10.1111/j.1479-8425.2007.00262.x 
  11. 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. https://doi.org/10.3389/fneur.2012.00061 
  12. 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), 75–77. https://doi.org/10.1111/j.1479-8425.2006.00193.x 
  13. Bannai, M., & Kawai, N. (2012). New therapeutic strategy for amino acid medicine: Glycine improves the quality of sleep. Journal of Pharmacological Sciences, 118(2), 145–148. https://doi.org/10.1254/jphs.11r04fm 
  14. File, S. E., Fluck, E., & Fernandes, C. (1999). Beneficial effects of glycine (Bioglycin) on memory and attention in Young and Middle-Aged Adults. Journal of Clinical Psychopharmacology, 19(6), 506–512. https://doi.org/10.1097/00004714-199912000-00004 
  15. Effect of glycine: Studying memory and behavioral changes in mice. (2018, September 1). PubMed. https://pubmed.ncbi.nlm.nih.gov/30150193/ 
  16. Guasch-Ferré, M., Hruby, A., Toledo, E., Clish, C. B., Martínez-González, M. A., Salas-Salvadó, J., & Hu, F. B. (2016). Metabolomics in Prediabetes and Diabetes: A Systematic review and Meta-analysis. Diabetes Care, 39(5), 833–846. https://doi.org/10.2337/dc15-2251 
  17. Cruz, M., Maldonado-Bernal, C., Mondragón-Gonzalez, R., Sanchez-Barrera, R., Wacher, N. H., Carvajal-Sandoval, G., & Kumate, J. (2008). Glycine treatment decreases proinflammatory cytokines and increases interferon-γ in patients with Type 2 diabetes. Journal of Endocrinological Investigation, 31(8), 694–699. https://doi.org/10.1007/bf03346417 
  18. Gannon, M. C., Nuttall, J. A., & Nuttall, F. Q. (2002). The metabolic response to ingested glycine. American Journal of Clinical Nutrition, 76(6), 1302–1307. https://doi.org/10.1093/ajcn/76.6.1302 
  19. Sugaya, K., Oh-Oka, H., Yamada, T., Miyata, M., Ashitomi, K., Kadekawa, K., & Nishijima, S. (2021). Dietary glycine improves urine storage symptoms in urology outpatients. Journal of Complementary and Integrative Medicine, 18(3), 617–620. https://doi.org/10.1515/jcim-2020-0282 
  20. Ding, Y., Svingen, G. F. T., Pedersen, E. R., Gregory, J. F., Ueland, P. M., Tell, G. S., & Nygård, O. K. (2016). Plasma glycine and risk of acute myocardial infarction in patients with suspected stable angina pectoris. Journal of the American Heart Association, 5(1). https://doi.org/10.1161/jaha.115.002621 
  21. Sekhar, R. V., Patel, S. G., Guthikonda, A. P., Reid, M., Balasubramanyam, A., Taffet, G. E., & Jahoor, F. (2011). Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. American Journal of Clinical Nutrition, 94(3), 847–853. https://doi.org/10.3945/ajcn.110.003483 
  22. Cordis, C. (2007, August 3). Taking a supplement of glycine, a food additive, helps to prevent degenerative diseases such as arthrosis or osteoporosis. CORDIS | European Commission. https://cordis.europa.eu/article/id/108690-taking-a-supplement-of-glycine-a-food-additive-helps-to-prevent-degenerative-diseases-such-as 
  23. Koopman, R., Caldow, M. K., Ham, D. J., & Lynch, G. S. (2017). Glycine metabolism in skeletal muscle. Current Opinion in Clinical Nutrition & Metabolic Care, 20(4), 237–242. https://doi.org/10.1097/mco.0000000000000383 
  24. Brind, J., Malloy, V., Augie, I., Caliendo, N., Vogelman, J. H., Zimmerman, J. A., & Orentreich, N. (2011). Dietary glycine supplementation mimics lifespan extension by dietary methionine restriction in Fisher 344 rats. The FASEB Journal, 25(S1). https://doi.org/10.1096/fasebj.25.1_supplement.528.2 
  25. Obata, F., & Miura, M. (2015). Enhancing S-adenosyl-methionine catabolism extends Drosophila lifespan. Nature Communications, 6(1). https://doi.org/10.1038/ncomms9332
  26. Liu, Y. J., Janssens, G. E., McIntyre, R. L., Molenaars, M., Kamble, R., Gao, A. W., Jongejan, A., Van Weeghel, M., MacInnes, A. W., & Houtkooper, R. H. (2019). Glycine promotes longevity in Caenorhabditis elegans in a methionine cycle-dependent fashion. In PLoS Genetics (Vols. 15–3, p. e1007633). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6424468/pdf/pgen.1007633.pdf 
  27. Inagawa, K., Kawai, N., Ono, K., Sukegawa, E., Tsubuku, S., & Takahashi, M. (2006). Assessment of acute adverse events of glycine ingestion at a high dose in human volunteers. Seikatsu Eisei, 50(1), 27–32. https://doi.org/10.11468/seikatsueisei.50.27
  28.    
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