Glycine is a dietary amino acid that also acts as a neurotransmitter, influencing both excitatory and inhibitory neural signaling in your brain.
Glycine reduces sleep latency or the time it takes to fall asleep, improves the quality of sleep, and increases the feeling of being well-rested after a night of sleep.
The improved sleep that is achieved with glycine supplementation can increase cognitive performance.
Glycine is a dietary amino acid that functions both as a building block of protein structures and in neurotransmission, as glycine itself can directly bind to receptors on neurons, regulating the function of these cells.
The structure of glycine:
The enzyme serine trans hydroxy-methylase (SHMT) converts the amino acid serine into glycine in neurons. (Figure 1).
Figure 1. Glycine biosynthethesis
Glycine is unique as a neurotransmitter since it functions in excitatory as well as inhibitory neural signaling, whereas most neurotransmitters tend to be excitatory or inhibitory but not both.
Glycine binds to glycine receptors for inhibitory neurotransmission.
Glycine has been shown to shorten EEG measured latency to sleep onset and to slow wave sleep, but without changing durations in REM and non-REM sleep.3
Glycine lessened subjective measures in daytime tiredness and increased performance in a task of psychomotor vigilance and attention.3
Glycine subjectively improved sleep quality by improving subjective measures such as "fatigue," "liveliness and peppiness" and "clear-headedness," as measured by the St. Mary's Hospital Sleep Questionnaire and Space-Aeromedicine Fatigue Checklist, according to a follow-up study4.
Glycine reduced psychomotor fatigue and improved reaction time in a psychomotor vigilance task in a 2012 study.
Figure 2. Improvements in reaction times during tasks of psychomotor vigilance are consistently improved up to two days after glycine enhanced sleep.5
A single case report from 2009 demonstrated daily Glycine ingestion over a five-year period lessened the symptoms of obsessive-compulsive disorder and body dysmorphic disorder.6
Glycine can be consumed at bedtime, in combination with other sleep-promoting nootropics, to enhance sleep.
Consider taking 450 mg to 3 grams of glycine just before bedtime to optimize sleep
The majority of individuals do not experience significant side effects when taking glycine orally, but there have been a few reports of nausea, vomiting, stomach upset, and drowsiness. There is not enough known about glycine supplementation during pregnancy and breastfeeding.
Glycine is approved as a dietary supplement component under provisions of the Dietary Supplement Health and Education Act of 1994. It is classified as generally recognized as safe (GRAS).
Kawai, N., Sakai, N., Okuro, M., Karakawa, S., Tsuneyoshi, Y., Kawasaki, N., . . . Nishino, S. (2015). The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology, 40(6), 1405-1416. doi:10.1038/npp.2014.326
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. doi:10.1111/j.1479-8425.2007.00262.x
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. doi:10.1111/j.1479-8425.2006.00193.x
Cleveland, W. L., DeLaPaz, R. L., Fawwaz, R. A., & Challop, R. S. (2009). High-dose glycine treatment of refractory obsessive-compulsive disorder and body dysmorphic disorder in a 5-year period. Neural Plast, 2009, 768398. doi:10.1155/2009/768398
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