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Glycine Research & Evidence

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Evidence Level

Moderate

Glycine has clean, consistent evidence for sleep improvement from Japanese research groups. Bannai et al. (2012) published the definitive crossover RCT showing 3g glycine improved sleep quality and next-day function. Inagawa et al. (2006) confirmed benefits using polysomnography. Kawai et al. (2015) elucidated the mechanism: glycine activates NMDA receptors in the suprachiasmatic nucleus (SCN), promoting peripheral vasodilation and core body temperature decrease, which mimics the natural thermoregulatory sleep onset signal. This mechanism is notable because it is entirely different from GABAergic sedation — glycine improves sleep quality without causing drowsiness or impairing wakefulness. Yamadera et al. (2007) provided additional supporting data in sleep-restricted individuals.

Evidence by Condition

ConditionStudied DoseEvidence
Sleep quality improvement3g before bedModerate
Next-day fatigue reduction3g before bedModerate
General relaxation1-3g as neededEmerging
Full Glycine Guide

References

  1. (). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology. DOI
  2. (). Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep and Biological Rhythms. DOI
  3. (). The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology. DOI
  4. (). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms. DOI