Glycine
Glycine is an amino acid studied for sleep quality and metabolic outcomes. Evidence is promising but still developing.
Overview
What is glycine?
Glycine is a conditionally essential amino acid produced by the body from serine, a non-essential amino acid.
Dietary glycine intake is readily obtained through consumption of animal meats, beans, and dairy products.
Glycine may reduce sleep latency by reducing core body temperature.
Dosage
A typical dose of glycine is around 2 to 5 grams per day.
For sleep, studies use a typical dose of 3 grams per day, taken before bed.
In studies examining schizophrenia patients, dosages of 2 to 60 grams per day have been used.
Effect graph
Effect heatmap
SupplementDEX Database
2 conditions for and rated at least stars. All purchase bands. No minimum star filter.
Database Snapshot
Most glycine research is concentrated in a handful of conditions.
- Schizophrenia accounts for 6 of 10 studies (60%).
- Sleep accounts for 4 of 10 studies (40%).
Dietary Sources
Top dietary sources
Ranked by amount per 100 g
Glycine is found in collagen, gelatin, and animal meats including tuna, chicken, lamb, turkey, fish, and shellfish.
- 1.77 g100 g
- 1.59 g100 g
- 1.57 g100 g
- 1.46 g100 g
- 1.44 g100 g
- 1.42 g100 g
- 1.19 g100 g
- 1.18 g100 g
Safety
Glycine is generally well-tolerated at the recommended dosages.
Dose windows
Short-term
Oral doses of up to 3 to 5 grams per day have safely been used.
Long-term
Oral doses of up to 60 grams per day for up to 8 weeks have been safely used.
Special populations
Pregnancy & breastfeeding
AvoidThe safety of glycine in pregnant or lactating women is unknown. Usage should be avoided.
Children
AvoidThe safety of glycine in children is unknown. Usage should be avoided.
Other notes
Information on the safety of topical glycine is limited and there is a lack of high-quality human studies. Studies use a typical dose of 3 grams per day for sleep, and much higher doses of up to 60 grams per day in schizophrenia patients.
Frequently Asked Questions
Takeaway
Glycine is a neurotransmitter and conditionally essential amino acid found in high concentrations in gelatin, collagen, tofu, animal meats, and other protein-rich foods.
Glycine may improve sleep quality and reduce the time required to fall asleep by reducing core body temperature.
In schizophrenia patients, glycine supplementation may reduce negative, but not positive symptoms of disease. Glycine may reduce the effectiveness of clozapine but not other neuroleptics.
References
Sources10 references
SupplementDEX uses only high-quality sources to determine supplement effectiveness.
SupplementDEX Database · Sleep
4 references1.SupplementDEX Database: Sleep — Nutritional Modulation of Sleep Latency, Duration, and Efficiency: A Randomized, Repeated-Measures, Double-Blind Deception Study2023
In a crossover RCT of 16 adults, a nutritional blend with glycine, tryptophan, magnesium, and tart cherry improved self-reported sleep quality versus placebo.
2.SupplementDEX Database: Sleep — The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers2012
In a study of 10 partially sleep-restricted volunteers, glycine 3 g before bedtime reduced daytime sleepiness and improved psychomotor vigilance the next day.
3.Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. See external sourceExternal source
4.Subjective effects of glycine ingestion before bedtime on sleep quality. See external sourceExternal source
SupplementDEX Database · Schizophrenia
6 references5.SupplementDEX Database: Schizophrenia — The effects of glycine on auditory mismatch negativity in schizophrenia2018
In an RCT of 12 schizophrenia patients, glycine 0.2 g/kg for 6 weeks did not significantly increase auditory mismatch negativity amplitude versus placebo.
6.SupplementDEX Database: Schizophrenia — Placebo-controlled trial of glycine added to clozapine in schizophrenia2000
In an 8-week RCT of 27 schizophrenia patients on clozapine, glycine 60 g/day did not improve positive, negative, or cognitive symptoms versus placebo.
7.SupplementDEX Database: Schizophrenia — Efficacy of high-dose glycine in the treatment of enduring negative symptoms of schizophrenia1999
In a 6-week RCT of 22 treatment-resistant schizophrenia patients, high-dose glycine 0.8 g/kg/day reduced negative symptoms versus placebo.
8.SupplementDEX Database: Schizophrenia — Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia1999
In a 12-week double-blind study of 19 clozapine-treated schizophrenia patients, glycine 30 g/day did not improve psychiatric symptom scores versus placebo.
9.SupplementDEX Database: Schizophrenia — Double-blind, placebo-controlled, crossover trial of glycine adjuvant therapy for treatment-resistant schizophrenia1996
In a 6-week crossover trial of 11 treatment-resistant schizophrenia patients, glycine 0.8 g/kg/day added to antipsychotics reduced negative symptoms versus placebo.
10.SupplementDEX Database: Schizophrenia — Amelioration of negative symptoms in schizophrenia by glycine1994
In a double-blind RCT of 14 medicated schizophrenia patients, glycine significantly improved negative symptoms versus placebo over the treatment period.