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Glycine

A simple amino with a surprisingly good sleep story — plus roles in collagen and glutathione.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsAmino acidsSleepRecovery

Glycine is the smallest amino acid and does a lot: it's a building block for collagen and glutathione, and an inhibitory (calming) signal in the brain.

Key takeaways

  • 3 g glycine before bed improved subjective sleep quality and next-day alertness in trials.1
  • It's a building block for collagen and the antioxidant glutathione.
  • It acts as a calming (inhibitory) neurotransmitter and gently lowers core temperature to aid sleep onset.
  • Cheap, sweet-tasting and very safe.

What it is

Glycine is a non-essential amino acid central to collagen (roughly a third of collagen is glycine), glutathione synthesis, and inhibitory neurotransmission.

The evidence

Small controlled studies found that 3 g before bed improved sleep quality, shortened time to fall asleep, and reduced daytime sleepiness with better memory performance the next day — partly via a mild drop in core temperature.1

Dose & how to use

3 g dissolved in water about an hour before bed (it tastes slightly sweet). Higher intakes are used for collagen/glutathione support.

Safety & who benefits

Very safe. Most relevant for light or unsatisfying sleep, and as a building block for people supporting collagen or antioxidant status.

Bottom line: a cheap, safe sleep aid with real (if modest) evidence — and a useful building block for collagen and glutathione.

References

Adult research summary for education, not a prescription. These are food supplements, not treatments for disease.

  1. Yamadera W, et al. Glycine ingestion improves subjective sleep quality, correlating with polysomnographic changes. Sleep Biol Rhythms 2007. onlinelibrary.wiley.com

This article summarises nutrition and exercise science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.