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Essentials: Timing Light for Better Sleep, Energy & Mood | Dr. Samer Hattar

Aug 21, 2025 35m 19s 15 insights
In this Huberman Lab Essentials episode, my guest is Dr. Samer Hattar, PhD, the Chief of the Section on Light and Circadian Rhythms at the National Institute of Mental Health. We discuss how light powerfully shapes mood, sleep, appetite, learning and overall mental health by aligning—or misaligning—our internal circadian clock. We explain practical protocols to support your circadian rhythm, including morning sunlight exposure, dim evening lighting and regular mealtimes. We also discuss strategies to manage jet lag, limit evening screen use, ease seasonal depression and improve focus by syncing light, sleep and food with natural biological rhythms. Read the episode show notes at hubermanlab.com.
Actionable Insights

1. Daily Morning Light Protocol

Get 10-30 minutes of natural light exposure to your eyes daily, preferably in the morning, even on cloudy days or in the shade, to entrain your circadian rhythm and improve overall well-being. If you miss a day, compensate with extra time on subsequent days to maintain consistency.

2. Manage Evening Light Exposure

Dim your lights to the minimum comfortable level in the evening, ideally letting natural darkness set in, to avoid disrupting your circadian clock and melatonin production. If using screens, avoid direct gaze, check quickly, and consider using red-spectrum dim lights (below 10 lux) for sleeping areas to minimize impact on sleep.

3. Optimize Sleep with Tripartite Model

Optimize your sleep by managing three factors: your homeostatic sleep drive (how long you’ve been awake), aligning your circadian clock with light-dark cycles, and minimizing disruptive light or stress in the evening. Considering all three together is essential for a beautiful and restorative sleep-wake cycle.

4. Jet Lag Travel Protocol

When traveling across time zones, immediately adopt the local eating schedule to help your body adjust, but critically manage light exposure based on your body’s internal time, not local time. Avoid bright light if the local morning is still your internal night to prevent delaying your clock further and worsening jet lag.

5. Advance or Delay Your Clock

To advance your sleep-wake cycle (sleep earlier), view bright light after your body’s lowest temperature point (typically 2-3 hours before your natural wake-up time). To delay your sleep-wake cycle (sleep later), view bright light before this low temperature point.

6. Consistent Meal Timing

Establish regular meal times daily, ideally within a 30-minute window, aligning with your natural circadian rhythm and active schedule. This practice, combined with appropriate light exposure, helps regulate hunger hormones and can support weight management.

7. Align for Peak Performance

Consciously align your daily activities, including work, focus, and exercise, with your body’s optimal timing by understanding and managing your circadian rhythm. This alignment can lead to improved performance, focus, and natural sleep-wake cycles without needing an alarm.

8. Avoid Internal Jet Lag

Prevent internal clock misalignment by ensuring regular outdoor light exposure and limiting bright artificial light exposure late at night, especially if staying indoors or using screens excessively. This prevents your body’s internal clock from drifting out of sync with the solar day, which can cause fatigue and mood issues.

9. Light’s Direct Mood Impact

Recognize that light exposure, beyond just regulating sleep, directly impacts mood, stress levels, learning, and memory through distinct brain pathways. Therefore, managing light exposure throughout the day is crucial for overall mental well-being and cognitive function.

10. Light for Image Blindness

Even if you are image blind, you still need to expose your eyes to light at particular times of day or night to entrain your circadian rhythm and avoid sleep problems. This is because non-vision-forming photoreceptors, which regulate the clock, remain active.

11. Discover Your Chronotype

To determine your optimal intrinsic rhythm (early bird, night owl), consistently expose yourself to morning sunlight and observe how it makes you feel. This process helps align your internal clock and can reveal if an earlier schedule improves your mental and physical health.

12. Troubleshoot Night Waking

If you consistently wake up in the middle of the night and can’t fall back asleep, consider that your circadian clock might be misaligned, potentially treating your sleep as a ’nap’ due to incorrect light exposure or an inappropriate bedtime. Re-evaluate your light hygiene and sleep schedule.

13. Re-establish Natural Seasonality

Consistently expose yourself to natural light daily to allow your body to better adapt to seasonal changes in light. This practice can help regulate energy levels and mood throughout the year, counteracting the disruptive effects of artificial light.

14. Daylight Saving Time Awareness

Be aware that daylight saving time changes, even by just one hour, can significantly disrupt your circadian rhythm and negatively impact your sleep, mood, and overall health due to cumulative misalignment. Take extra care to maintain consistent light exposure during these transitions.

15. Prioritize Light for Health

Adopt a mindset of prioritizing the optimization of daily light exposure as a fundamental and powerful tool for improving sleep, wakefulness, productivity, and overall well-being. View this ‘photon’ intervention as a primary strategy rather than solely relying on pharmaceutical solutions.