Glycine
Glycine is the smallest amino acid and one of the most abundant in the body: it is found in collagen and acts as a neurotransmitter with a calming effect.
3 g a day.
What it is
In rats it lowers core body temperature, one of the signals that accompany falling asleep: this could be the mechanism behind its effect.
What it is used for
The quiz suggests it when your answers justify it. It usually appears with these goals:
What the evidence says
Trials in people that point the same way, but still few, small or funded by the manufacturer.
Small trials in Japan (3 g before bed) showed better subjective sleep quality and less fatigue the next day.
| Year | What was studied | What was found | Source |
|---|---|---|---|
| 2012 | The review | Review of studies by the group that has researched glycine most: taken before bed, it improved subjective sleep quality in people prone to insomnia. In rats it lowered core body temperature, the possible mechanism. | Bannai and KawaiJournal of Pharmacological Sciences |
| 2007 | Sleep quality | Trial in volunteers with unsatisfactory sleep: 3 g of glycine before bed improved subjective sleep quality, with consistent changes on polysomnography. | Yamadera et al.Sleep and Biological Rhythms |
| 2012 | Daytime performance | Trial in healthy volunteers whose sleep was cut by 25% for three nights: 3 g of glycine before bed reduced next-day fatigue compared with placebo, with a trend towards less sleepiness. | Bannai et al.Frontiers in Neurology |
What to look for on the label
- Pure glycine powder: it is the cheapest form and the one used in the studies.
Precautions
- Very well tolerated.
- If you take clozapine, do not take it without asking first.
Where to find it
Products whose label meets what this profile asks for: form, dose per serving and nothing that contradicts it. Three at most: quality of the active comes first and, among the best, we look for one option in each price range. We choose by composition, not by who pays. The shops are European or ship to Europe.
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Life ExtensionShips from the Netherlands€€€High endLife Extension
Glycine 1,000 mg
1 g per capsule
For the reference dose3 capsules: 3 gView at Life Extension (opens in a new tab)Meets the criteria.
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VegaveroShips from Germany€€Mid rangeVegavero
Glycine powder
Pure glycine
For the reference dose3 g a dayView at Vegavero (opens in a new tab)Meets the criteria.
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HSNShips from Spain€BudgetRaw Series
Glycine powder
Pure glycine, no additives
For the reference dose3 g (the scoop holds 5 g)View at HSN (opens in a new tab)Meets the criteria.
We link to the shop; we do not sell anything. Today we earn no commission on any link. If we ever do, the link will say so and the selection will not change: the label decides. Labels checked on 2 November 2026; check the one on the pack before you buy. All these shops deliver to the EU; some of their pages open in Spanish. How we are funded.
Nearby in the library
Is it for you?
The quiz decides from your answers, not from a profile.
Profile reviewed on 3 November 2026. Sources: EFSA, Regulation (EU) 432/2012 and published studies. Image: Chemical apparatus. Engraving by J. Pass, 1801. Wellcome Collection, public domain.
General information based on published scientific evidence and EU law. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle, and are not intended to diagnose, treat or prevent any disease.
Do not exceed the daily dose stated on each product. If you take medication, have a medical condition or have any doubts, ask your doctor or pharmacist.