Why your body's internal clock struggles to keep up with flight speeds
In short: When you cross multiple time zones, your brain moves much faster than your biological rhythms can process. This mismatch, known as jet lag, creates a physiological strain as your molecular circadian clocks struggle to re-sync with your new environment.
Jet lag is the physiological strain caused by traveling across multiple time zones, a term that entered the dictionary in 1966 via Horace Sutton. At its core, the condition is a misalignment between your internal circadian rhythms—the roughly 24-hour biological cycles governing alertness and body temperature—and the light-dark cycle of your destination. While these rhythms can function independently, they are highly sensitive to external inputs, most notably light.
The severity of the condition often depends on the distance traveled. Flying across three or more time zones typically triggers symptoms such as insomnia, daytime drowsiness, headaches, fatigue, and even digestive issues like nausea or constipation. The direction of travel also matters; for instance, if you 'gain' hours, you may feel sleepy during daylight hours when your body is accustomed to being awake.
While common folk remedies like aromatherapy or pressure points lack evidence, light exposure is a scientifically proven tool for 'phase shifting.' Bright light in the early morning can trigger a phase advance, helping you wake up earlier, while light near bedtime can cause a phase delay. Research from Rush University Medical Center in Chicago demonstrated that three days of morning light exposure could shift circadian rhythms by an average of 2.1 hours, potentially allowing travelers to adjust to new time zones up to two days faster.
To manage the transition, experts suggest staying hydrated, remaining active by walking or stretching, and avoiding excessive caffeine or alcohol. While melatonin is a natural hormone that signals sleep, the NHS notes there is insufficient evidence to recommend melatonin tablets specifically for treating jet lag.
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Sources
- Summary by Intellect · source: The Science of Jet Lag... And How To Prevent It
- Also: What Is Jet Lag?
- Also: Jet lag
- Also: How to Prevent Jet Lag | Scientific American
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