Glycine
Powder
Moderate
Some good studies, not many repeats
Moderate: objective PSG outcomes but small samples and a single sponsor (Ajinomoto).
In sleep-lab studies people fell asleep faster and reached deep sleep sooner, because it lowers the body's core temperature a little. They also felt less sleepy the next day.
Three grams of glycine before bed lowered core body temperature and, in polysomnography studies, helped people fall asleep faster and reach deep sleep sooner, with less daytime sleepiness the next day. The trials are small and from one research group, so we grade it moderate.
NMDA-mediated vasodilation drops core temperature — the same physiological trigger your body uses to initiate sleep.
People who take long to fall asleep or run warm at night. Very safe; 3 g powder tastes mildly sweet.
We compare each effect with how much that number normally swings from one night to the next. An effect smaller than the swing is real, but you will not see it in a week of data.
- Sleep onset latency (PSG)Too small to seeeffect: 5 minnormal swing: ±20 min
- Time to slow-wave sleepVisible over weekseffect: 10 minnormal swing: ±25 min
What to buy
- ✓Pure glycine powder (no fillers)
- ✓3 g scoop
- ✕Capsules — you'd need 4–6 per dose
- · Very benign; occasional mild GI upset.
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3 g before bed; sweet-tasting, dissolves in water or tea.
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A bigger tub for daily use. Glycine tastes sweet and dissolves in water or tea, which is why nobody bothers with capsules at 3 g a dose.
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See all on AmazonEvery result, next to the line that means no effect
Each diamond is a study's best estimate. The thin line shows how sure the study was: the shorter the line, the more certain the result.
- Sleep onset latency (PSG)min · Yamadera 2007−5.00[not given]
- Time to slow-wave sleepmin · Yamadera 2007−10.0[not given]
Each unit gets its own scale, so numbers are never mixed on one line. When a study gave no range, we leave it blank instead of inventing one.
2 studies over 5 years
The studies
- 1.Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changesSleep and Biological Rhythms · 2007 · crossover · n = 11
Shortened sleep onset and faster descent into slow-wave sleep without altering architecture.
- 2.The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteersFrontiers in Neurology · 2012 · crossover · n = 8
Less daytime sleepiness and better performance under sleep restriction.
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