TLDR;
This video provides a comprehensive guide to optimising your daily routine for better sleep and wakefulness by focusing on light exposure. It emphasises the importance of getting sufficient sunlight in the morning to set your circadian clock, adjusting eye sensitivity with evening sunlight, and minimising light exposure at night. The key takeaways include:
- Maximise morning light exposure (aim for 100,000 lux before 9-10am) to activate your circadian clock.
- Use evening sunlight to decrease eye sensitivity to light, providing a buffer against late-night light exposure.
- Minimise bright light exposure between 10pm and 4am to avoid disrupting your circadian rhythm.
Perfect Circadian Schedule [0:00]
The ideal daily routine involves maximising light exposure, ideally sunlight, during the hours you want to be awake and alert, and minimising light exposure when you want to be asleep or drowsy. It's crucial to avoid damaging your eyes by looking at excessively bright lights. If it's dark in the morning, use overhead artificial lights to stimulate the melanopsin cells in your retina, which helps activate your circadian clock.
Morning Sunlight [1:26]
Sunlight, even through cloud cover, provides a significant amount of photon energy. Aim to expose yourself to at least 100,000 lux before 9:00 a.m. or 10:00 a.m. It's important not to stare directly at very bright lights. The circadian clock setting mechanism involves neurons in the eye sending electrical signals to the brain, and this system accumulates photons slowly.
How Circadian Clock Setting Works [2:55]
Brief exposure to computer or phone screens in the morning, which emit around 500 to 1,000 lux, won't significantly impact your circadian clock unless sustained for an extended period (100 minutes or more). To capture enough photons to set your circadian clock effectively, aim to do so before the "circadian dead zone" in the middle of the day. This process relies on light exposure through the eyes, not vitamin D absorption through the skin, and is crucial for both mental and physical well-being.
Going Outside vs Artificial Lighting [4:12]
Going outside is the best way to achieve the 100,000 lux target before 9:00 a.m. Even on a cloudy day, outdoor light levels can be remarkably high. If sunlight is limited due to location or weather conditions, artificial lights can be used as a substitute. While artificial lights can provide the necessary photons, sunlight has unique qualities that make it a superior stimulus. Devices like light pads or ring lights can be used, but sunlight remains the preferred option.
Watching the Sunset [6:30]
Looking at sunlight around sunset adjusts down the sensitivity of your eyes. This is beneficial because while a lot of photon energy is needed in the morning to wake up the system, very little photon energy is needed to reset the clock after 8:00 p.m. Therefore, it's important to avoid bright light between 10:00 p.m. or 11:00 p.m. and 4:00 a.m. Seeing afternoon light provides leeway to view screens and overhead lights later without disrupting the circadian clock.
How Long it Takes to Reset Melatonin & Cortisol [8:09]
Studies from the University of Colorado have shown that two days of waking up with the sun and avoiding light at night can reset melatonin and cortisol rhythms. Other factors like consistent exercise and meal times can also reinforce the circadian clock. The key is to get at least 100,000 lux of light exposure to the eyes in the morning, avoid excessive light exposure at night, and use evening light to adjust retinal sensitivity. It only takes about 1,000 to 1,500 lux of light energy to shift your clock in the middle of the night.
