Using Light for Health

Thank you for joining the Huberman Lab Neural Network — a once-a-month newsletter with science and science-related tools for everyday life. This newsletter aims to provide you with actionable information in a condensed form.

In Episode #68, I discuss how light directs a number of key aspects of our physiology to strongly impact our overall health and well-being. Light directly impacts our mood, our sleep, our ability to wake up and focus, our hormone levels, our immune system and our ability to cope with stress. Given that light has tremendous positive effects, this newsletter aims to outline zero-cost tools to harness the power of light to improve mental and physical health.

Morning Sunlight to Set Your Mind and Body Correctly

I consider viewing morning sunlight in the top five of all actions that support mental health, physical health and performance.

These are:

1. Sleep
2. Movement
3. Nutrients (Macro and Micro)
4. (Sun)Light
5. Relationships

As regular listeners of Huberman Lab can attest, “View morning sunlight!” is one of my common refrains. Viewing sunlight within the first hours of waking (as soon as you can, even if through cloud cover) increases early-day cortisol release (the ideal time for elevated cortisol) and prepares the body for sleep later that night. A morning spike in cortisol will also positively influence your immune system, metabolism and ability to focus during the day.

Further, morning sunlight helps regulate your “circadian clock” — the body’s mechanism for anticipating when to wake up and go to sleep — and it manages other biological processes like hunger and body temperature.

On a sunny morning, get outside for 5-10 minutes. You can do more if you have time, and feel free to use the time outside to exercise, walk, eat a light breakfast or journal in the sunlight. Even on overcast days, there is still enough sunlight to trigger positive effects, but you’ll need to increase the time outside to at least 15-20 minutes. If it’s dark when you wake up or if the weather prevents you from going outside, flip on as many bright indoor artificial lights as possible — then get outside as soon as the sun is out.

Contacts and eyeglasses (even those with UV protection) are fine to wear when viewing morning sunlight. However, don’t use sunglasses or blue blockers during morning sunlight-viewing — you won’t get the maximum effects from the morning sunlight. Face toward the sun. As always, never look directly at the sun or view the sun (or any light) in a way that causes pain; just close your eyes and blink as needed to protect your eyes. Note: trying to do all this through a windshield or window won’t work; too many of the relevant wavelengths are filtered out.

Afternoon Sunlight to Reinforce Your Sleep

Later in the day, try to get outside in the afternoon. The particular wavelengths of the sun when it is low in the sky (yellows and oranges, in contrast with blue) come through even if it’s overcast. Sunlight viewed in the late afternoon/evening communicates to the brain’s circadian clock that it is evening and time to begin the process of transitioning to sleep that night.

Also, on the occasional day you miss getting outside early in the morning, the afternoon sunlight serves as a second “anchor point” for your brain and body to know the time/season, in order to maintain the consistency of your circadian clock.

Note: Afternoon sunlight is known to reduce some (not all!) of the ill effects of late-night brightness from artificial sources.

Using Light to Improve Daytime Energy & Focus

In the morning and until the midafternoon, use bright overhead lights to facilitate the release of dopamine, norepinephrine, epinephrine (molecules associated with motivation, attention and drive) and optimal amounts of cortisol to maximize your alertness and focus for work or other activities. Increase the ambient light of your workspace rather than increasing the brightness of the computer screen. Ideally, also place your desk near a window, as the natural sunlight signals the brain to stay alert and focused.

In the late afternoon, follow the natural rhythm of the sun and start to dim the work environment. Try to reduce blue light exposure to aid the transition to sleep later. Turn off overhead lights; use lamps or softer lighting and dim the computer screen.

Avoid Bright Lights at Night to Protect Mood & Neurotransmitters

In my conversation with Dr. Samer Hattar, a senior investigator and chief of the section on Light and Circadian Rhythms at the National Institutes of Mental Health (NIMH), he discussed the importance of viewing morning sunlight, specifically UVB rays, blue light, to improve mood, increase energy, regulate appetite and increase dopamine release. He also warned that UVB light exposure from artificial sources/screens at night (10 p.m.-4 a.m.) decreases dopamine levels and negatively impacts feelings of depression and anxiety. Once in a while is fine, but if you are looking at your phone or turning on bright lights, especially overhead lights, between 10 p.m. and 4 a.m. on a regular basis, your health will suffer.

Inexpensive Red Lights to Keep Nighttime Cortisol Low & Melatonin High

Keeping your cortisol low at night is essential for sleep and immune system health. Also, the hormone melatonin naturally rises in the late evening to produce feelings of sleepiness and stays elevated through the beginning of the night. However, bright light powerfully inhibits melatonin. So, if you need to get up in the middle of the night (to use the bathroom or check on children, etc.), try using no light or very dim light. Or you could try to use amber or red light (longer wavelengths), as this type of light more minimally impacts melatonin levels. Inexpensive red “party light” bulbs work fine. I shift to using red lights around 9 p.m., and it has greatly improved my sleep. Of course, turn them off at bedtime.

In fact, for high-quality, deep sleep, ensure that your room is very dark while you sleep. Mason et al. demonstrated that even dim light exposure during sleep impairs cardiometabolic function and increases insulin resistance.

Bright Red Light

“Red-light therapy” is becoming more common. It has, indeed, been shown to improve eyesight in individuals older than 40, but it must be done in the early daytime. It can also assist with acne, wound healing and more, but for all those effects one needs a special red light. They are commercially available but carry some cost (hundreds to thousands of dollars). That said, if you want to learn more, I discuss these and the science and tools in our episode titled “Using Light (Sunlight, Blue Light & Red Light) to Optimize Health.”

Shift Work

Avoid looking at bright light in the middle of your individual sleep cycle. Use dark window shades and dim lighting to get good quality sleep. Ideally, try to stay on the same schedule for a minimum of two weeks at a time, so your circadian clock can better predict your sleep cycle. Those with young children or those working night shifts should see our episode on jet lag and shift work for science-supported tools that help.

Hormones

Thus far, all these tips are focused on viewing sunlight, but there is also an advantage to getting sunlight on your skin. Parikh et al. found that skin exposure to afternoon sunlight for about 30minutes (such as by wearing shorts and short-sleeved t-shirts) increased testosterone, estrogen, mood and libido in both men and women. To follow their protocol, get outside in shorts/t-shirts for ~20-30 minutes in the afternoon, 2-3x per week minimum. Don’t sunburn!

There are other light-based tools in Episode #68, but the above eight tips are the biggies. #1 and #4 are the most important.

Stay Connected

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Thank you for your interest in science!

Best wishes,
Andrew