Glycine

Authored by Sumeet Sharma

Take Home Points

• Glycine is a dietary amino acid that also acts as a neurotransmitter, influencing both excitatory and inhibitory neural signaling in your brain.

• Glycine reduces sleep latency or the time it takes to fall asleep, improves the quality of sleep, and increases the feeling of being well-rested after a night of sleep.

• The improved sleep that is achieved with glycine supplementation can increase cognitive performance.

Origin

Glycine is a dietary amino acid that functions both as a building block of protein structures and in neurotransmission, as glycine itself can directly bind to receptors on neurons, regulating the function of these cells.

Structure

The structure of glycine:

The enzyme serine trans hydroxy-methylase (SHMT) converts the amino acid serine into glycine in neurons. (Figure 1).

Figure 1. Glycine biosynthethesis

Effects on Cognition

Glycine is unique as a neurotransmitter since it functions in excitatory as well as inhibitory neural signaling, whereas most neurotransmitters tend to be excitatory or inhibitory but not both.

Glycine binds to glycine receptors for inhibitory neurotransmission.

Glycine binds to NMDA receptors for excitatory neurotransmission.¹Glycine induces sleep through upregulation of NMDA receptor activity in the suprachiasmatic nucleus.²

Sleep and Attention

Glycine has been shown to shorten EEG measured latency to sleep onset and to slow wave sleep, but without changing durations in REM and non-REM sleep.³

Glycine lessened subjective measures in daytime tiredness and increased performance in a task of psychomotor vigilance and attention.³

Glycine subjectively improved sleep quality by improving subjective measures such as "fatigue," "liveliness and peppiness" and "clear-headedness," as measured by the St. Mary's Hospital Sleep Questionnaire and Space-Aeromedicine Fatigue Checklist, according to a follow-up study⁴.

Glycine reduced psychomotor fatigue and improved reaction time in a psychomotor vigilance task in a 2012 study.

Figure 2. Improvements in reaction times during tasks of psychomotor vigilance are consistently improved up to two days after glycine enhanced sleep.⁵

Obsessive behavior

A single case report from 2009 demonstrated daily Glycine ingestion over a five-year period lessened the symptoms of obsessive-compulsive disorder and body dysmorphic disorder.⁶

How to Take

Glycine can be consumed at bedtime, in combination with other sleep-promoting nootropics, to enhance sleep.

Consider taking 450 mg to 3 grams of glycine just before bedtime to optimize sleep

Side Effects

The majority of individuals do not experience significant side effects when taking glycine orally, but there have been a few reports of nausea, vomiting, stomach upset, and drowsiness. There is not enough known about glycine supplementation during pregnancy and breastfeeding.

Safety

Glycine is approved as a dietary supplement component under provisions of the Dietary Supplement Health and Education Act of 1994. It is classified as generally recognized as safe (GRAS).