Sleep/Cognition

Glycine

A simple amino acid that may improve sleep quality and next-day alertness in adults with occasional poor sleep.

score

evidence

Safe

risk

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Overview

Forms

Safety

Stack

Quick Take

Reasonable low-risk sleep aid to try at 3 g before bed, but evidence is still small and mostly short-term.

Glycine is a nonessential amino acid found in collagen-rich foods like gelatin, bone broth, meat, fish, and legumes. It acts as an inhibitory neurotransmitter and NMDA co-agonist, and before bed it may help the normal drop in core body temperature that supports sleep. Small human trials suggest better subjective sleep quality, slightly easier sleep initiation, and better next-day alertness after poor sleep. It is most relevant for adults with occasional sleep dissatisfaction, not severe insomnia.

Potential benefits

Improves sleep quality

May improve next-day alertness

May shorten sleep onset

May improve sleep efficiency

Protocol

Amount

3 g

Frequency

Once nightly

When

30-60 minutes before bed, mixed in water; consistency matters more than exact timing.

Onset Time

Often within 1-3 nights; judge fairly after 1-2 weeks

Who Should Consider

Adults with occasional poor sleep

People who feel unrefreshed after short sleep

Those wanting a non-hormonal bedtime aid

People who prefer a cheap single-ingredient sleep trial

Food Sources

Gelatin powder (~2-3 g per 10 g)
Collagen peptides (~2 g per 10 g)
Bone broth (~0.5-1.5 g per cup, highly variable)
Slow-cooked skin/connective tissue meats (~1-2 g per serving)
Fish skin and connective tissue cuts (~1-2 g per serving)
Beans or lentils (~0.5-1 g per cup cooked)

How It Works

Glycine activates inhibitory glycine receptors and also acts at the NMDA receptor. Taken before bed, it appears to increase peripheral heat loss and slightly lower core body temperature, a physiologic cue that helps the brain transition into sleep; better sleep can then carry into next-day alertness.

Updated 5/19/2026