Melatonin vs Glycine
Hormonal sleep aid vs amino acid - which approach is better?
The Verdict
The short answer: Glycine for sleep quality, melatonin for circadian timing. Use both strategically.
Choose melatonin if: You have jet lag, shift work, or delayed sleep phase (can't fall asleep until late).
Choose glycine if: You sleep enough hours but wake unrested, run hot at night, or want to improve sleep quality.
The science says: Melatonin is a timing signal, not a sedative. Lower doses (0.3-0.5mg) work better than high doses. Glycine improves actual sleep quality. Different problems, different solutions.
Head-to-Head Comparison
| Metric | Melatonin | Glycine |
|---|---|---|
| Evidence Rating | A Better | B+ |
| Circadian Rhythm Reset | Very High Better | None |
| Sleep Quality | Minimal | High Better |
| Morning Alertness | Can impair | Improves Better |
| Jet Lag Recovery | Very High Better | Minimal |
| Temperature Effect | Slight cooling | Significant cooling Better |
| Dependency Risk | Low (possible) | None Better |
| Side Effects | Grogginess, vivid dreams | Very rare Better |
| Optimal Dose | 0.3-0.5mg (most use too much) | 3g |
| Safe Long-term | Uncertain | True Better |
Choose Melatonin if you...
- Recovering from jet lag
- Shift worker adjusting schedule
- Delayed sleep phase (natural night owl)
- Need to reset circadian rhythm
- Trouble falling asleep at desired time
- Short-term use only
Choose Glycine if you...
- Sleep enough but wake tired
- Run hot and wake sweaty
- Want better deep sleep
- Looking for long-term solution
- Sensitive to hormonal supplements
- Already tried melatonin without success
Targeted Protocol (Recommended)
Use each for its strength:
Melatonin: Short-term, low-dose for timing issues - Jet lag: 0.5mg at destination bedtime - Schedule shifts: 0.3mg at new target bedtime - Occasional use only
Glycine: Ongoing use for quality - 3g nightly, 30-60 min before bed - Safe for continuous use
For travel: Use both temporarily, then transition to glycine only.
Sample Weekly Schedule
The Science
Melatonin
Mechanisms
- Signals darkness to suprachiasmatic nucleus
- Shifts circadian phase when timed correctly
- Mild sedative effect at high doses
- Antioxidant properties
- Regulates sleep-wake cycle timing
Key Research
- 0.5mg as effective as higher doses for sleep onset
- Effective for jet lag when timed properly
- High doses may suppress natural production
Glycine
Mechanisms
- Lowers core body temperature
- Inhibitory neurotransmitter action
- Improves blood flow to extremities
- Enhances slow-wave sleep
- Supports next-day cognitive function
Key Research
- 3g glycine improves subjective sleep quality
- Reduces fatigue and improves daytime performance
- Safe for long-term use with no tolerance
Frequently Asked Questions
Why do most melatonin products have such high doses?
Marketing, not science. Studies show 0.3-0.5mg is optimal. Higher doses (3-10mg common in stores) can cause grogginess and may suppress natural production.
Can I become dependent on melatonin?
Physical dependency is unlikely, but psychological reliance can develop. It's best used short-term for circadian issues, not nightly for years.
Is glycine safe to take every night?
Yes. Glycine is a naturally occurring amino acid your body makes. Long-term supplementation shows no adverse effects in studies.
Can I take both together?
Yes, they work through different mechanisms. Useful for jet lag or sleep schedule transitions. For ongoing use, glycine alone is preferred.
Why does high-dose melatonin make me groggy?
Excess melatonin lingers into morning and can disrupt natural cortisol awakening response. Use lowest effective dose (0.3-0.5mg).