Glycine C

«Glycine» — evidence level C. Dosage: 3 g 30-60 minutes before sleep. In sleep studies this is the most studied dose; higher doses gave no additional effect. Source: PMID 37874350, permanent link to the source in the list below.

Glycine is the simplest amino acid, acting as an inhibitory neurotransmitter in the spinal cord and brainstem and as a co-agonist of NMDA receptors. When taken before sleep it lowers core body temperature and speeds up the onset of sleep. In connective tissue, glycine is the main amino acid of collagen. That is why most studies are devoted to sleep and collagen peptides rather than to muscle performance.

Free glycine powder, slightly sweet in taste, dissolves well in water. Sublingual tablets are a common but less studied form

• Shortens the time to fall asleep and reduces nighttime awakenings
• As part of collagen peptides before sleep it improved sleep quality and cognitive measures in physically active men with sleep complaints
• Participates in the synthesis of collagen, hemoglobin and creatine in the body

• Sports performance and body composition were not assessed in the studies - conclusions about sleep cannot be transferred to sports results
• The evidence base is narrow: isolated small studies, often with collagen peptides rather than pure glycine
• Weak data on the effect on glucose levels with long-term intake of large doses
• Drowsiness and dizziness are possible in some people

• With clonazepam and other anticonvulsants - summation of the sedative effect is possible
• Enhanced sedation has been described with clozapine
• Alcohol increases drowsiness

• Under 18 years: Usually well tolerated; there are insufficient data on intake by children to improve sleep, and sleep patterns are corrected non-pharmacologically
• Pregnancy and lactation: There are no safety data for glycine supplements during pregnancy and lactation
• Severe renal or hepatic failure - only as prescribed by a physician
• Concurrent use of sedative drugs - consultation is required
• Sleep disorders with breathing pauses - supplements do not replace treatment

• Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints · Thomas C, Kingshott RN, Allott KM · European journal of nutrition, 2024 · PMID 37874350

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