Glycine

The simplest amino acid and an inhibitory neurotransmitter that acts at glycine receptors and as a co-agonist at NMDA receptors. Glycine is one of the most well-evidenced and accessible sleep aids, with multiple randomized controlled trials demonstrating improvements in sleep quality, reduced sleep onset latency, and enhanced next-day cognitive performance. It lowers core body temperature — a key physiological trigger for sleep onset — and modulates central nervous system excitability.

• Activates NMDA receptors in the suprachiasmatic nucleus (SCN) to promote peripheral vasodilation and core body temperature drop
• Acts as an inhibitory neurotransmitter at glycine receptors in the brainstem and spinal cord
• Modulates serotonin metabolism in the prefrontal cortex for improved next-day cognition
• Reduces inflammatory cytokines (TNF-alpha, IL-6) that impair sleep quality

• Clozapine therapy (glycine may interact with clozapine efficacy)
• Severe renal impairment (high-dose use requires monitoring)
• Generally considered safe for most populations

Store at room temperature (15–25°C (59–77°F)) in a cool, dry place. Highly stable with a long shelf life.

Multiple double-blind, placebo-controlled RCTs published in Sleep and Biological Research (Yamadera et al., 2007; Bannai et al., 2012; Inagawa et al., 2006) demonstrated that 3g of glycine before bedtime significantly improved subjective sleep quality, reduced sleep onset latency, and enhanced next-day performance on cognitive tasks. Polysomnography data showed faster transition to slow-wave sleep. The mechanism was elucidated by Kawai et al. (2015), who demonstrated that glycine acts on NMDA receptors in the SCN to trigger peripheral vasodilation and core temperature reduction — a physiological prerequisite for sleep onset. Glycine has GRAS (Generally Recognized as Safe) status with the FDA.