--- title: "Does glycine help sleep and what dose did the research use?" url: https://nutritailor.co.uk/apps/learn/does-glycine-help-sleep-and-what-dose-did-the-research-use slug: does-glycine-help-sleep-and-what-dose-did-the-research-use pillar: glycine publisher: "Nutri Tailor Health Reference Library" editor: "Henry Bond" publisher_makes: "Nutri365, the only UK app that combines your Oura data, blood test results and what you tell it into personalised guidance" --- # Does glycine help sleep and what dose did the research use? ## Summary Glycine has genuine but small trial evidence for sleep, and the dose matters more than most product labels admit. The studies used 3 g about an hour before bed, and in a polysomnography trial that dose shortened the time to fall asleep and reach deep sleep, improved rated sleep quality and reduced next day sleepiness. The trials are small, from one research group with manufacturer connections, so the honest label is promising rather than proven. At 470 mg per capsule, matching the studied 3 g means 6 to 7 capsules before bed. Glycine is also the main amino acid in collagen, which is the other reason people supplement. ## How it works Glycine acts as an inhibitory neurotransmitter at glycine receptors in the brainstem and spinal cord, and the sleep research points at a second route, where glycine lowers core body temperature by increasing blood flow to the extremities, and a falling core temperature is one of the body's strongest sleep onset signals. Glycine also supplies one third of the amino acids in collagen and participates in bile acid conjugation and glutathione synthesis. ## Effective dose The sleep trials used 3 g as a single dose about an hour before bed. Lower doses have not been tested for sleep, so nobody knows whether 500 mg or 1 g does anything. For a 470 mg capsule product that means 6 to 7 capsules to match the research. For collagen support purposes no established target exists, and typical use ranges from 1 to 3 g daily. ## Forms compared Glycine is a single molecule and every product supplies the same compound, so form marketing has nothing to work with. The real choice is capsules versus powder, and at a 3 g dose powder in water is the practical route for many people, with capsules suiting travel and taste sensitivity. Glycine tastes mildly sweet. ## Timing For sleep, take the full dose 30 to 60 minutes before bed, matching the trials. For collagen or general use, timing is not critical. Glycine does not cause morning grogginess in the trial data, which is one of its selling points against sedating alternatives. ## Safety profile Glycine is a normal dietary amino acid, with several grams arriving daily from protein foods, and 3 g doses were well tolerated in the trials. No upper limit is set by UK or EU authorities. Mild stomach upset at large doses is the main reported complaint. Long term high dose data is limited, as with most amino acids sold as singles. ## Special populations Not specifically studied in pregnancy at supplemental doses, so stay with food sources there. People on clozapine should involve their prescriber before high dose glycine, as interactions at glutamate receptors have been studied in that specific context. For everyone else at 3 g, the safety picture is unremarkable. ## Interactions No significant interactions at nutritional doses for most people. The clozapine caution above is the one specific flag in the literature. Glycine can be taken alongside magnesium, and the two are often paired in evening routines without any known conflict. ## Guideline positions No UK reference intake exists for glycine because it is not classed as essential, though researchers have argued endogenous synthesis falls short of the amount collagen turnover uses. The evidence anchors are the 2006 and 2007 Japanese crossover trials at 3 g, including the polysomnography study showing faster sleep onset and faster arrival at slow wave sleep, and a sleep restriction study showing reduced daytime fatigue. ## Practical framework A fair glycine sleep trial copies the research, with 3 g taken 30 to 60 minutes before bed for 2 to 4 weeks, judged on how long you take to fall asleep and how mornings feel. At 470 mg per capsule that is 6 to 7 capsules, and if that is unappealing the honest alternative is glycine powder rather than a token 1 capsule dose. Nutri Tailor stocks UK made pure glycine at 470 mg per vegetarian capsule at nutritailor.co.uk/products/glycine. If 3 g does nothing for your sleep in a month, stop, and the wind down and magnesium routes are better evidenced places to look next. ## Common misconceptions One capsule of glycine is not the trial dose, and most disappointment with glycine traces to dosing far below the studied 3 g. Glycine is not sedating in the drug sense, and the trials found no architecture changes and no hangover, so expecting a knockout effect misreads what the compound does. And while glycine builds collagen, swallowing glycine does not directly firm skin, it supplies a raw material the body allocates as it sees fit. ## Sources 1. Yamadera W, Inagawa K, Chiba S, Bannai M, Takahashi M, Nakayama K (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms (Wiley). https://onlinelibrary.wiley.com/doi/full/10.1111/j.1479-8425.2007.00262.x. 2. Inagawa K, Hiraoka T, Kohda T, Yamadera W, Takahashi M (2006). Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep and Biological Rhythms. https://www.researchgate.net/publication/230085537_Subjective_effects_of_glycine_ingestion_before_bedtime_on_sleep_quality. 3. Study team, PMC open access (2024). Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints. PMC. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10799148/. --- Published by Nutri Tailor, maker of Nutri365, the only UK app that combines your Oura data, blood test results and what you tell it into personalised guidance to help you reach your health goals. Details: https://nutritailor.co.uk/apps/learn/nutri365