Glycine

Glycine is a non-essential amino acid — the body can synthesize it, though many people benefit from additional dietary or supplemental intake. It is the smallest amino acid structurally and serves an extraordinary range of biological functions — from building collagen (the most abundant protein in the body) to regulating key neurotransmitter systems in the brain and spinal cord.

As a neurotransmitter, Glycine plays a dual role — acting as an inhibitory signal in the brainstem and spinal cord while also serving as a co-agonist at NMDA glutamate receptors in the brain.  This dual function makes Glycine uniquely positioned to support both physical relaxation and cognitive calm — two of the most important prerequisites for quality sleep.

Glycine supports sleep through several complementary mechanisms:

- Core Body Temperature Reduction — Glycine promotes vasodilation in peripheral blood vessels, redirecting blood flow to the skin and lowering core body temperature. Core temperature drop is one
of the most critical physiological triggers for sleep onset — this is why a cool room promotes better sleep

- Inhibitory Neurotransmission — as an inhibitory neurotransmitter in the brainstem and spinal cord,
Glycine promotes muscle relaxation and reduces motor neuron excitability — supporting the physical
stillness associated with deep sleep

- REM Sleep Enhancement — research shows Glycine supplementation increases time spent in REM sleep, the sleep stage critical for memory consolidation, emotional processing, and cognitive restoration

- NMDA Receptor Co-Agonism — Glycine modulates NMDA receptor activity in the brain, influencing
neurotransmitter balance in ways that support cognitive calm

- Morning Alertness — uniquely, Glycine improves next-day alertness and reduces daytime sleepiness
even when total sleep time is the same — supporting sleep quality over sleep quantity

Glycine has an excellent safety profile as one of the body's most fundamental amino acids:

- Extremely well tolerated at standard doses
- May cause mild nausea at very high doses — rare at supplemental amounts
- Generally recognized as safe (GRAS) by the FDA
- Water soluble — excess excreted safely
- May enhance effects of antipsychotic medications in clinical contexts — consult doctor if onpsychiatric medications
- Safe for long-term daily use at standard doses
- Not recommended during pregnancy or nursing without medical supervision

- Bannai et al. (2012) — Published in Sleep and Biological Rhythms, randomized crossover trial found Glycine supplementation (3g before bed) significantly improved subjective sleep quality, reduced daytime
sleepiness, and improved cognitive performance the following day.

- Kawai et al. (2015) — Published in Neuropsychopharmacology, demonstrated Glycine promotes sleep by lowering core body temperature through peripheral vasodilation — establishing the primary mechanism for its sleep-promoting effects.

- Bannai & Kawai (2012) — Review in Frontiers in Neurology comprehensively documented Glycine's
role as both an inhibitory neurotransmitter and sleep-promoting agent, with particular emphasis on its ability to increase REM sleep time.

- File et al. (1999) — Research confirmed Glycine's anxiolytic properties through NMDA receptor modulation, supporting its use for stress-related sleep difficulties.