Host: Andrew Huberman (@hubermanlab)
Dr. Samer Hattar (@SamerHattar) is Chief and Senior Investigator of Light and Circadian Rhythms at the National Institutes of Health (NIH). Dr. Hattar is a world-renowned expert on how viewing light at particular times adjusts our mood, ability to learn, stress and hormone levels, appetite, and mental health.
In this episode of Huberman Lab, Dr. Huberman hosts Dr. Samer Hattar to discuss how to use light to optimize the sleep-wake cycle, the timing of food intake, exercise, and mental and physical health.
Light exposure has an unconscious influence on the level of the cell, behavior, circadian cycle
Sunlight exposure adjusts circadian rhythm and associated behavior to 24-hour periods
One of the strongest adaptations of survival is the adaptation to and anticipation of light
Light allows animals to anticipate seasonality
A landmark discovery in 2000 found that cells in the eye communicate day and night to the brain
  • Even blind people benefit from viewing light for regulation of circadian rhythm
Cones in the eye see color and adapt to varying intensities of light
Best way to interact with light: get outside (even on cloudy days it’s enough) 15 minutes daily shortly after waking, ideally without sunglasses
The circadian system needs to be synchronized to light/outdoors to know where you are in time
There is not enough research on artificial light to know the correct intensity – but it’s likely helpful to have exposure during the day
Sleep-wake cycles will suffer if you stay indoors and are not getting natural light
Camping experiment: studies have shown that camping for two days with no screens, sleeping and waking whenever feels natural – can adjust circadian rhythms
Can’t determine whether you are naturally an early bird or night owl? Get light exposure in the morning and see how you feel
Animals have a ‘light hunger’
Consider avoiding blue light blocking glasses because it’s changing natural optics of the eye and adaptation properties of the retina – just dim the blue and increase the warmness of the light
Evening light viewing tip: keep your home dim/dark, to the minimum amount of light you need to see comfortably; explore using red light
When you view light, it could make you feel happy/unhappy, stressed/less stressed, enhance learning/decrease learning, etc.
If you disrupt light, effects on stress are profound
The more we deviate from intrinsic rhythm, the more we see increased rates of depression, anxiety, and adverse mental health outcomes
Even if light exposure isn’t affecting the circadian clock, it might be affecting mood, focus, learning, stress, homeostasis
Suicide is highest in spring: theory is that lack of light in winter can cause depression so sunlight in spring gives people energy to act on feelings
Patients with bipolar disorder have more sensitivity to light
Light viewing and feeding behavior interact in ways that support one another
Tip: have regular meals times that fit your circadian clock
Most of the time we eat, it’s mostly because we just want to – not because we’re hungry
Tip #1: We make better food choices when we are not anticipating meals but have a set schedule (+/- 30 minutes)
Tip #2: Limit eating to active times of circadian rhythm (i.e., during the day)
Social rhythm affects sleep, how much you eat
Repeatedly staying up late can take about two weeks to recover
Travel Tip #1: Change mealtimes and adjust light exposure to advance and delay clock according to the time zone you will be traveling to
Travel Tip #2: Exercise, view light, and eat a meal first-morning post-travel