Jet lag (circadian desynchrony) occurs when your suprachiasmatic nucleus (SCN) — the brain's master circadian clock — is set to one time zone while your environment and schedule demand alignment to another. The SCN requires approximately 1 day per time zone crossed to fully resynchronise. A London-to-Singapore flight crossing 8 time zones theoretically requires 8 days of unaided recovery.
The evidence-based protocol below typically reduces recovery time to 2-4 days for eastward travel and 1-3 days for westward travel (eastward is harder — it requires advancing the clock, which is physiologically more difficult than delaying it).
Step 1: Melatonin — The Core Intervention
Melatonin is a chronobiotic (circadian phase-shifter), not a sedative. It signals to the SCN that it is night — advancing or delaying the clock based on when it is taken relative to your current rhythm. The Cochrane review by Herxheimer & Petrie (2002) remains the definitive evidence base: melatonin taken at destination bedtime significantly reduces jet lag severity and recovery time.
- Dose: 3-5mg — effective at lower doses but 5mg produces faster phase shifting in most adults
- Time: destination bedtime — not departure time, not when you feel tired. Take it at 10pm in Tokyo even if you feel wide awake because your body thinks it is 2pm in London
- Duration: 3-5 days at destination — continue for first 3-5 nights until resynchronisation is complete
- Critical timing rule: Early melatonin (6-11pm destination time) advances the clock (helps eastward travel). Late melatonin (after midnight) delays the clock (helps westward)
Step 2: Light Exposure — As Powerful as Melatonin
Light is the strongest zeitgeber (time-giver) for the circadian clock. Strategic light exposure accelerates resynchronisation and strategic light avoidance prevents counter-productive delay.
| Travel direction | Morning bright light exposure | Evening light exposure | Action |
|---|---|---|---|
| Eastward (advancing clock e.g., UK → India) | Seek bright light in early morning at destination (6-9am) | Avoid bright light after 8pm destination time | Use blue-light blocking glasses from 7pm if needed |
| Westward (delaying clock e.g., India → US West) | Avoid early morning light for first 1-2 days (sleep later) | Seek bright light in evening (5-8pm destination) | Maximise evening outdoor exposure |
Step 3: The Supporting Supplement Stack
- Melatonin 3-5mg: Destination bedtime, nights 1-5 at new location
- Magnesium Glycinate 200-400mg: 30 minutes before destination bedtime. GABA-modulatory effect improves sleep quality at the new schedule; reduces the hyperarousal that prevents sleep when the body's clock is misaligned
- Caffeine management: Time caffeine to destination schedule from day 1 — if at a destination where morning is 9am local, take caffeine at 9am local regardless of how you feel. This trains alertness cues to the new schedule
- Vitamin D 2,000 IU: In the morning at destination — Vitamin D synthesis is normally triggered by daytime sunlight; supplementing in the morning reinforces the day signal for circadian photoentrainment
- Hydration: Aircraft cabins maintain 10-20% relative humidity (vs outdoor 40-60%). Dehydration amplifies jet lag symptoms. Target 500ml water per hour of flight; avoid alcohol and excess caffeine in-flight
Day-by-Day Protocol Timeline
Example: London → Mumbai (IST = GMT+5:30)
| Time | London time equivalent | Action |
|---|---|---|
| Day -1 (departure day) | — | Shift bedtime 1-2 hours earlier. Take melatonin 2-3 hours earlier than usual |
| Day 0 (flight day) | — | Adjust watch to IST immediately. Sleep if it is night in IST. Avoid alcohol; stay hydrated |
| Night 1 (Mumbai) | ~6:30pm London | Take 5mg melatonin at 10pm IST. Take Mg glycinate 200mg. Blackout curtains |
| Day 1 (Mumbai) | — | Bright outdoor light 7-9am IST. Standard caffeine at 8am IST. No naps after 3pm IST |
| Nights 2-4 | — | Continue melatonin 3-5mg. Continue Mg glycinate. Earlier bedtime if possible |
| Day 5 | — | Most users are fully resynchronised by this point with the protocol |