Glycine

Glycine (amino acid)

Last updated 2026-05-19 · 3 primary citations

Mechanism

Falling asleep depends on your body cooling down by about a degree. Glycine triggers that cool-down by opening small blood vessels in your hands and feet, releasing heat. It also calms the brain's arousal signals. The result: shorter time to fall asleep, deeper slow-wave sleep, less daytime fatigue the next day.

Why we use it

Glycine is the single most studied non-prescription sleep ingredient at the gram scale. It doesn't make you groggy, doesn't build tolerance, and doesn't interact with hormones. For perimenopausal women whose biggest sleep complaint is 'I can't fall asleep' or 'I wake up at 3am,' it's the cleanest first answer.

How we dose it

Hericea uses 3,000 mg per serving (per PM packet). The clinical trial range that anchors this dose is 3,000 mg/day.

3 grams — the exact dose proven on sleep-lab equipment to help people fall asleep faster and stay in deep sleep longer. Glycine is mildly sweet, so it also doubles as a natural flavor for the PM packet.

Quality & sourcing

Pharma-grade USP; ≥99% purity.

Free-amino-acid form; dissolves cleanly.

Primary literature

Yamadera W et al. (2007)

Sleep Biol Rhythms

Source →

Sleep-lab RCT (crossover)

Glycine 3 g before bedtime improved subjective sleep quality and, on sleep-lab equipment, shortened the time it took to fall asleep and to reach deep sleep — without changing the natural shape of sleep.

Direct sleep-lab proof. This is the trial our 3-gram dose comes from.

DOI 10.1111/j.1479-8425.2007.00262.x

Bannai M et al. (2012)

Front Neurol

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RCT (sleep restriction) · 7 people

Glycine 3 g per night when participants were forced to sleep less reduced next-day fatigue and sleepiness compared to placebo.

Most relevant to imperfect-sleep populations — perimenopausal women rarely get a full undisturbed night. This trial tests glycine in those exact conditions.

Kawai N et al. (2015)

Neuropsychopharmacology

Mechanism (animal)

Explains exactly how glycine triggers the body's natural cooling-for-sleep response by widening blood vessels in the periphery.

The mechanism paper — confirms the body-cooling story isn't just a hypothesis.