Legendre P. The glycinergic inhibitory synapse. Cell Mol Life Sci C 2001 585 [Internet]. 2001 [cited 2022 Sep 22];58(5):760–93. Available from: https://link.springer.com/article/10.1007/PL00000899
Glycine
Glycine is a conditionally essential amino acid. Unlike most other nootropics, it is an inhibitory neurotransmitter in the brain (1), and also acts as a co-agonist within the NMDA neurotransmitter system (2). It is a major component in the synthesis of collagen, and hence vitally important for the structural strength of connective tissues (3). These properties make Glycine an ideal candidate as a sleep- and focus-promoting nootropic.
Sleep
In a randomised placebo-controlled crossover trial, 3000mg supplementation lead to significant subjective improvement in several areas of validated sleep quality scales, including liveliness and clear-headedness (4). Another study showed similar subjective effects alongside matching polysomnography (sleep study) data (5).
Focus
Several other papers also show improvement in attention and recognition tasks following supplementation, including in sleep-restricted individuals (5,6).
Safety Evidence
Glycine is one of the most popular sleep-aiding nootropics, and has been shown to be safe to ingest despite the comparatively large recommended daily dosing, without any serious adverse effects or increased daytime sleepiness even in excessive amounts (7).
Read More About the Science
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2
Thomson AM. Glycine is a coagonist at the NMDA receptor/channel complex. Prog Neurobiol. 1990 Jan 1;35(1):53–74.
3
Li P, Wu G. Roles of dietary glycine, proline, and hydroxyproline in collagen synthesis and animal growth. Amin Acids 2017 501 [Internet]. 2017 Sep 20 [cited 2022 Sep 22];50(1):29–38. Available from: https://link.springer.com/article/10.1007/s00726-017-2490-6
4
Inagawa K, Hiraoka T, Kohda T, Yamadera W, Takahashi M. Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep Biol Rhythms [Internet]. 2006 Feb 1 [cited 2022 Sep 22];4(1):75–7. Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1479-8425.2006.00193.x
5
Yamadera W, Inagawa K, Chiba S, Bannai M, Takahashi M, Nakayama K. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms [Internet]. 2007 Apr 1 [cited 2022 Sep 22];5(2):126–31. Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1479-8425.2007.00262.x
6
Bannai M, Kawai N, Ono K, Nakahara K, Murakami N. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol [Internet]. 2012 [cited 2022 Sep 22];3. Available from: https://pubmed.ncbi.nlm.nih.gov/22529837/
7
INAGAWA K, KAWAI N, ONO K, SUKEGAWA E, TSUBUKU S, TAKAHASHI M. Assessment of Acute Adverse Events of Glycine Ingestion at a High Dose in Human Volunteers. SEIKATSU EISEI (Journal Urban Living Heal Assoc. 2006;50(1):27–32.