Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Glycine | L-Theanine | |
|---|---|---|
| Category | Amino Acids | Amino Acids |
| Standard Dose | 3-5g daily | 100-200mg daily (or as needed for acute anxiety/focus) |
| Timing | 3g before bed for sleep (core body temperature reduction). Divided doses during day for glutathione support. Powder in water has a mildly sweet taste. | Flexible: morning for calm focus (stack with caffeine), before stressful events, or evening for relaxation/sleep onset. Onset: 30-60 minutes oral, 15-20 min sublingual. |
| Cycle Duration | ongoing | ongoing or as needed |
| Evidence Level | strong_human | strong_human |
Glycine is the simplest amino acid with profound neurological and metabolic roles. It is an inhibitory neurotransmitter acting at glycine receptors (strychnine-sensitive) in the brainstem and spinal cord, inducing a drop in core body temperature that facilitates sleep onset. It is also an obligatory co-agonist at the NMDA receptor glycine binding site, modulating excitatory neurotransmission. Metabolically, glycine is the rate-limiting amino acid for glutathione synthesis (glutathione = glycine + cysteine + glutamate), a key substrate for collagen synthesis (every 3rd amino acid), essential for creatine synthesis, bile acid conjugation, heme synthesis, and one-carbon metabolism.
3-5g daily
3g before bed for sleep (core body temperature reduction). Divided doses during day for glutathione support. Powder in water has a mildly sweet taste.
ongoing
L-Theanine (gamma-glutamylethylamide) crosses the blood-brain barrier via the large neutral amino acid transporter. It increases alpha brain wave activity (8-13 Hz, associated with relaxed alertness), enhances GABA, serotonin, and dopamine levels in the brain, and antagonizes glutamate excitotoxicity by blocking glutamate binding at AMPA, kainate, and NMDA receptors. It also increases BDNF and NGF expression, supporting neuroplasticity. The combination of glutamate antagonism and GABA/serotonin enhancement produces anxiolysis without sedation — a 'calm focus' state.
100-200mg daily (or as needed for acute anxiety/focus)
Flexible: morning for calm focus (stack with caffeine), before stressful events, or evening for relaxation/sleep onset. Onset: 30-60 minutes oral, 15-20 min sublingual.
ongoing or as needed
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