Glycine is best known as an amino acid building block of collagen, abundant in our skin and bones. What is less known is how important glycine is for getting good sleep.

Glycine is the smallest and simplest amino acid and is found throughout the human body, with many important functions.  It reduces general inflammation by boosting the synthesis of glutathione. (McCarty et al., 2018) and serves as the precursor for numerous important organic compounds such as creatine, purines, porphyrins, and bile salts. In the brain, free glycine acts as an inhibitory neurotransmitter, exerting a calming effect in the central nervous system.

Research shows taking glycine before bedtime improves sleep. In a randomized double-blind crossover study, 19 adult females with poor sleep quality were given 3 grams of glycine or placebo at bedtime. Glycine improved next day fatigue, “liveliness and peppiness”, and “clear-headedness” (Inagawa et al., 2006). In a single blinded crossover study, 11 healthy adults with baseline poor sleep were given 3 grams of glycine or placebo before bedtime in the hospital setting over two consecutive nights. Glycine improved sleep onset, sleep satisfaction, and sleep efficiency. Glycine improved next day sleepiness and improved performance on memory recognition tasks. Polysomnography showed that glycine shortened time to sleep onset without disrupting sleep architecture. This contrasts with hypnotic drugs that induce sleep but comes at the expense of disrupting sleep architecture by reducing relative time in slow wave and REM sleep (Yamadera et al., 2007).

How does glycine promote good sleep?

Glycine promotes good sleep by reducing core body temperature. Normally, core body temperature drops at sleep onset, continues to decrease during sleep, and then rises as a person wakes up. Glycine passes into the brain passively, then acts on NMDA receptors in the suprachiasmatic nucleus (SCN), an area of the brain that regulates circadian rhythms, resulting in increased blood flow to the skin, heat loss, and subsequent drop in core body temperature (Bannai & Kawai, 2012).

Most people do not get enough glycine to meet their needs.

Glycine is a semi-essential amino acid. This means the body can make some of it on its own but cannot meet the body’s demands without obtaining it from the diet. The average adult synthesizes 3 grams of glycine on its own and obtains another 1.5-3 grams of glycine from the diet. However, to support the needs of all metabolic uses including keeping up with the rate of collagen turnover, most adults need an additional 10 grams of glycine per day for optimal health (Meléndez-Hevia et al., 2009).

People can adapt to low protein-low glycine diets by decreasing the rate of collagen turnover, but this comes at a cost because collagen gets damaged with age and doesn’t function as well. When protein is abundant in the diet, and glycine is readily available, the body has the resources to repair itself by producing new collagen. When glycine is abundant, more glycine is made available to the brain to promote good sleep, mood, and energy.

Risk factors for glycine deficiency include older age, inadequate protein intake that is common with the standard American diet, vegetarian/vegan diet, diabetes, obesity, and deficiencies in micronutrients required for the synthesis of glycine (eg. iron and B vitamins).

Glycine is inexpensive, safe, and well tolerated even at high doses. In one study, no side effects occurred when 12 healthy subjects were given 9 grams of glycine during the daytime. Day time use did not cause drowsiness (Inagawa et al., 2006). There were no adverse effects even when given at very high doses for the treatment of schizophrenia, eg. 20 grams three times a day (Heresco-Levy et al., 2004; Javitt et al., 2001).

Dietary glycine is abundant in collagenous foods, eg. chicken and fish with the skin on, bone in cuts of meat, and homemade bone broth. You can tell a bone broth is rich in glycine when it becomes gelatinous in the refrigerator. One cup of good bone broth provides approximately 3 grams of glycine. Supplemental collagen powders can be another good source of glycine.

When treating sleep problems, I find that taking pure glycine in its free form is best. It comes in a powder that has a pleasant, mildly sweet taste, which can be mixed into a wide variety of beverages before bed. It is also available in 1-gram capsules that many people find more convenient.  The usual dose is 3 grams one hour before bed. The benefits are usually felt the very next day. Glycine has a gentle effect. It helps set the stage for good sleep without inducing noticeable drowsiness. For moderate to severe insomnia, glycine alone is unlikely to be sufficient, but it can be layered safely with any other sleep aid and help them work better. My patients have reported deeper, more refreshing sleep, with positive changes to their energy and mood the next day. A few of my patients have even reported better dreams after taking glycine.

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References

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

Heresco-Levy, U., Ermilov, M., Lichtenberg, P., Bar, G., & Javitt, D. C. (2004). High-dose glycine added to olanzapine and risperidone for the treatment of schizophrenia. Biological Psychiatry, 55(2), 165–171. https://doi.org/10.1016/S0006-3223(03)00707-8

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 (Journal of Urban Living and Health Association), 50(1), 27–32. https://doi.org/10.11468/seikatsueisei.50.27

Javitt, D. C., Silipo, G., Cienfuegos, A., Shelley, A.-M., Bark, N., Park, M., Lindenmayer, J.-P., Suckow, R., & Zukin, S. R. (2001). Adjunctive high-dose glycine in the treatment of schizophrenia. International Journal of Neuropsychopharmacology, 4(4), 385–391. https://doi.org/10.1017/S1461145701002590

McCarty, M. F., O’Keefe, J. H., & DiNicolantonio, J. J. (2018). Dietary Glycine Is Rate-Limiting for Glutathione Synthesis and May Have Broad Potential for Health Protection. Ochsner Journal, 18(1), 81–87.

Meléndez-Hevia, E., De Paz-Lugo, P., Cornish-Bowden, A., & Cárdenas, M. L. (2009). A weak link in metabolism: The metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis. Journal of Biosciences, 34(6), 853–872. https://doi.org/10.1007/s12038-009-0100-9

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

Medical Disclaimer: The information mentioned in this article is not intended to diagnose, treat, cure, or prevent any disease. The information provided is for educational purposes only and is not intended to replace the relationships with your medical provider(s). Before initiating any treatment, please first consult with your licensed medical provider.