The Effects of Glycine on Subjective Daytime Performance in Partially Sleep-Restricted Healthy Volunteers
Key Finding
Glycine (3g before bed) improved sleep quality, reduced daytime fatigue, and enhanced next-day cognitive performance.
Plain-English Summary
This randomized, double-blind, placebo-controlled crossover study examined the effects of glycine on sleep quality and next-day performance in 11 healthy volunteers with chronic sleep restriction. Participants consumed 3 grams of glycine before bedtime.
Glycine supplementation significantly improved subjective sleep quality and reduced daytime fatigue and sleepiness. Polysomnography data showed that glycine shortened sleep onset latency and improved sleep efficiency without altering sleep architecture.
Participants also showed improved cognitive performance on psychomotor vigilance tasks the following day, indicating better restoration from sleep. Glycine appears to work by lowering core body temperature through vasodilation and potentially modulating NMDA receptors and glycine receptors in the brain. The amino acid promotes faster transition to deeper, more restorative sleep stages. Glycine was completely safe with no side effects.