{"ok":true,"entry":{"slug":"glycine","kind":"supplement","name":"glycine","aliases":["l-glycine","glycine powder"],"brands_sg":["NOW Foods","Life Extension","Thorne"],"class":"amino acid","tags":["sleep"],"use_for":"sleep quality (small trials) · main amino acid in collagen","use_after":"before bed · trials gave 3 g about 30 min before sleep","use_duration":null,"take_with":"water · tastes sweet (like glucose)","pros":["3 g at bedtime improved subjective sleep (small trials)","shortened time to fall asleep on polysomnography","the body makes ~45 g a day; diet adds ~3–5 g"],"cons":["sleep trials were tiny and short (one had 7 subjects)","no ul set · no dose-response safety trials in humans","sleep trials had ajinomoto authors (one used its staff)"],"dose_note":"sleep trials used 3 g about 30 min before bed; usual dietary intake is ~2.7–4.7 g a day; no rda or ul exists; the ~10 g/day 'collagen' figure comes from cell-culture modelling, not human trials","dosage":{"ul":null,"unit":"g","fda_dv":null,"rda_ai":null,"ul_status":"none_established","population":"general adult","hsa_max_daily":null},"ul_status":"none_established","sg_class":null,"cautions":["under 18 or pregnant — sleep trials were in adults (one all-male, 30–61 y)","long-term or high-dose use — no dose-response safety trials exist; ask your doctor first"],"clashes":[],"sources":[{"id":"yamadera2007","url":"https://link.springer.com/article/10.1111/j.1479-8425.2007.00262.x","label":"Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes (Yamadera et al., Sleep Biol Rhythms 2007;5:126–131)","quote":"3 g … before bedtime … Glycine improved subjective sleep quality and sleep efficacy (sleep time/in-bed time) … shortened PSG latency both to sleep onset and to slow wave sleep without changes in the sleep architecture … Glycine lessened daytime sleepiness","accessed":"2026-08-27"},{"id":"bannai2012","url":"https://europepmc.org/article/PMC/PMC3328957","label":"The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers (Bannai et al., Front Neurol 2012;3:61)","quote":"each participant took flavored glycine (3 g) or flavored placebo … 30 min before bedtime … Statistical analysis was performed on seven subjects … This was a randomized single-blinded crossover trial … approximately 45 g of endogenous glycine is synthesized … and 3–5 g of glycine is ingested from the daily diet … Ten healthy, male volunteers (30–61 years of age; average, 41.4 years) who were employed at Ajinomoto Co., Inc. … Frontier Research Labs, Institute for Innovation, Ajinomoto Co., Inc.","accessed":"2026-08-27"},{"id":"elango2023","url":"https://europepmc.org/article/PMC/PMC10334138","label":"Tolerable Upper Intake Level for Individual Amino Acids in Humans: A Narrative Review of Recent Clinical Studies (Elango, Adv Nutr 2023;14)","quote":"currently, there are no recommendations set by national health agencies for tolerable upper intake levels (UL) for amino acids because of a lack of well-conducted human dose-response trials … there are no systematic dose-response clinical trials among the remaining dispensable amino acids … [Table 2, daily dietary intake] Glycine 2.7 [g/d mean, EPIC] … 4.7 [g/d mean, NHANES] … 7.8 [g/d, 99th percentile]","accessed":"2026-08-27"},{"id":"depazlugo2018","url":"https://europepmc.org/article/PMC/PMC6153947","label":"High glycine concentration increases collagen synthesis by articular chondrocytes in vitro (de Paz-Lugo et al., Amino Acids 2018;50:1357)","quote":"Glycine, which is 33% of collagen residues, has been typically classified as a 'non-essential' amino acid … a normal intake of 1.50-3.00 g/day … glycine should be added to it as a nutritional supplement in high amounts, about 10 g/day [authors' modelled proposal; in-vitro study]","accessed":"2026-08-27"},{"id":"razak2017","url":"https://europepmc.org/article/PMC/PMC5350494","label":"Multifarious Beneficial Effect of Nonessential Amino Acid, Glycine: A Review (Razak et al., Oxid Med Cell Longev 2017)","quote":"The taste of glycine is sweet like glucose … Glycine is the simple amino acid with no L or D chemical configuration … In collagen, glycine is located at every third position","accessed":"2026-08-27"},{"id":"iherb_sg_glycine","url":"https://sg.iherb.com/c/glycine","label":"iHerb Singapore — Glycine category (SGD pricing, delivery to Singapore)","quote":"NOW Foods, Glycine, Pure Powder, 1 lb (454 g) … Life Extension, Glycine, 1,000 mg, 100 Vegetarian Capsules … Thorne, Glycine, 250 Capsules (500 mg per Capsule)","accessed":"2026-08-27"}],"brand_certs":[{"brand":"Thorne","example":null,"programme":"NSF Certified for Sport","matching_products":0,"brand_total_certified":66}],"updated_at":"2026-08-30T17:59:39.960259+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}