Circadian Rhythm
Helps regulate natural sleep-wake cycles
TL;DR
Circadian rhythm health is anchored by light exposure timing, consistent sleep-wake times, and meal timing. Melatonin is the only supplement with strong evidence for phase-shifting — and dose/timing matter more than quantity.
Why It Matters
The circadian system coordinates sleep, hormone release, metabolism, and immune function via the suprachiasmatic nucleus, entrained primarily by light. Disruption (shift work, social jet lag) is linked to metabolic, cardiovascular, and mood disorders. Melatonin taken at the correct circadian time (not just at bedtime) shifts the clock; mistimed doses can shift it the wrong way.
How to Measure
Track sleep/wake times and subjective alertness for 2 weeks; wearables can approximate rhythm stability.
Biomarkers
Optimization Protocol
Anchor: consistent wake time + morning outdoor light (10–30 min). If phase-shifting is needed (jet lag, delayed phase): low-dose melatonin 0.5–3 mg, timed 4–6 hours before current natural sleep onset for phase advance — timing is direction-critical. Avoid bright light late evening.
Lifestyle Levers
- •Consistent wake time daily
- •Morning bright light exposure
- •Dim lights 2 h before bed
- •Regular meal timing
- •Avoid late-night eating
Supporting Supplements
Glycine
Glycine before bed improves sleep quality by supporting the core temperature drop that initiates sleep.
Melatonin
Melatonin is the only supplement with strong evidence for shifting the circadian clock — when timed correctly.
Supporting Research
Frequently Asked Questions
Typical Timeframe
1–2 weeks to shift phase; stability requires ongoing consistency.
Research Summary
My Notes
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This information is for educational purposes only. Always consult a healthcare professional before starting any supplement regimen.