Glycine vs L-Theanine: The Night vs The Day
Both Glycine and L-Theanine are amino acids that promote "calm." But they are used at opposite times of the day.
L-Theanine is the "Daytime Calm." It helps you focus at work. Glycine is the "Nighttime Cool." It helps you drop into deep sleep.
| Feature | Glycine | L-Theanine |
|---|---|---|
| Primary Time | Before Bed | Morning / Afternoon |
| Mechanism | Lowers Body Temp | Alpha Brain Waves |
| Taste | Sweet | Umami / Savory |
| Drowsiness | Yes (at 3g+) | No |
Mechanisms: Cooling vs Tuning
Glycine: The Cool Down
Glycine triggers peripheral vasodilation (widening of blood vessels in skin). This dumps heat from your core.
A dropping core temperature is the biological signal for the brain to release melatonin and enter SWS (Slow Wave Sleep).
L-Theanine: The Frequency Tuner
L-Theanine crosses the blood-brain barrier and increases Alpha activity (8-13 Hz). This is a state of "wakeful relaxation."
It quiets the noise but keeps the light on. Ideal for meditation or flow states.
Which One Matches Your Goal?
For Refreshing Sleep
Winner: Glycine.
L-Theanine helps you fall asleep if your mind is racing, but Glycine actually improves the *quality* of the sleep cycles. It reduces grogginess the next day.
For Caffeine Jitters
Winner: L-Theanine.
Glycine won't help with coffee jitters. L-Theanine is the perfect antidote to caffeine side effects.
The Verdict
Choose Glycine if: You want to wake up feeling more rested or need to lower your body temperature at night.
Choose L-Theanine if: You want mental clarity, focus, and calm during the day.