NOW Foods Glycine Pure Powder Review

NOW lists the serving at a quarter teaspoon, roughly 1 g. For the studied sleep dose you take about one rounded teaspoon, which is close to 3 g — the amount used across the human sleep studies (Yamadera 2007; Bannai 2012, PMID 22529837). Stir it into water or warm tea 30 to 60 minutes before bed. It is the one small nuance versus the other two powders, which portion 3 g per scoop; here you measure a little more yourself.

Yes — it is 100% pure glycine, vegan and non-GMO, with no fillers or blend. The sleep evidence is for plain glycine by itself, so anything labeled 'glycine complex,' NAC+glycine, or magnesium glycinate is a different product and was disqualified. NOW's pure glycine powder is exactly the free-form glycine you want for the 3 g pre-bed dose.

Among the most respected in the industry. NOW operates extensive in-house analytical laboratories, manufactures under GMP, and is one of the most frequently audited supplement brands. For a commodity amino acid, that QC pedigree is exactly the assurance you want — the molecule is identical everywhere, so what matters is verified purity, and NOW's in-house testing operation is a genuine strength.

Recognition and availability. NOW is a household name stocked in most health stores, so it is the simplest offline backup if you run out, and many buyers simply trust a brand they already know. The trade-off is small: it costs a touch more per gram than the bulk-bag specialists, and its 1 g label serving means you measure a rounded teaspoon for 3 g rather than taking one pre-portioned scoop. On quality it is right there with the top powders.

1. [1] Bannai 2012 PMID 22529837 — The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. In healthy volunteers whose sleep was restricted for three nights, 3 g of glycine before bed significantly reduced subjective daytime fatigue and sleepiness and improved reaction-time performance versus placebo. The best-replicated glycine sleep finding — but a small study, and the authors are affiliated with a glycine manufacturer (noted for transparency).
2. [2] Kawai 2015 PMID 25533534 — The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Mechanistic study in rats: oral glycine promoted sleep and lowered core body temperature by acting on NMDA receptors in the suprachiasmatic nucleus (the master circadian clock), increasing skin blood flow and heat loss. Provides the leading biological explanation for glycine's sleep effect — but it is an animal study, so extrapolation to humans is indirect.
3. [3] Yamadera 2007 — Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. In volunteers with unsatisfactory sleep, 3 g of glycine before bed improved subjective sleep quality and, on polysomnography, shortened latency to sleep onset and to slow-wave sleep. The canonical human glycine-sleep study and the source of the 3 g dose — but small (~11 subjects) and published in a journal PubMed does not index, so no PMID exists. Cited honestly without a fabricated identifier.