Welcome,

On a winter day during my medical training, I walked out of the hospital’s doors into darkness. I added a count to my tally: 43 consecutive days since I had seen the sun. I had never been more unhappy or unhealthy.

My body is not designed to thrive under artificial light and neither is yours. Yet, most of us spend 90% of our time indoors, which means by the time we hit 40, we’ve already spent 36 years inside.

Spending so much time under artificial light makes our days darker than they should be and our nights brighter. This is very disorienting for the body’s internal clock, which must keep trillions of biochemical processes running in perfect harmony.

A growing body of science is demonstrating the damaging impact this has on our mood and wellbeing. A recent study of 85,000 people published in Nature found that exposure to less light during the day and more light at night were linked to increased rates of depression, self-harm, PTSD, and psychosis. 

What you should do about it:

Making simple changes to how and when you are exposed to light and dark will boost your mood and dramatically improve your health.

Go outside for 10 minutes in the morning and evening to set your clock

At sunrise and sunset, the sky is filled with “low-angle solar light,” a unique combination of blues, oranges, pinks and reds. Much like a fingerprint, our retinas read this combination of wavelengths and intrinsically know that the sun is rising or setting.

Fun fact: We evolved color vision to tell time, not to watch HD TV or identify all of the watermelons in a bag of jelly bellies. 

Go outside in the middle of the day

Get as much exposure to natural daylight as possible. The more exposure you get the better you will feel.

While your local Costco might feel bright, light intensity in even the brightest indoor spaces is less than 5% of the light intensity outside on a cloudy day.

Stop scrolling, turn off overhead lights, and use lamps for darker nights

Every night around 10pm, I tell myself that I will not look at my phone. Then, I get into bed and immediately start scrolling. This is pretty much like shining a flashlight in my eyes and then expecting to peacefully drift off into deep slumber.

Artificial sources of indoor light are up to 80x more intense than moonlight and the wrong color.

In the evenings, our eyes are most sensitive to light coming from above, so turn off overhead lights. Use lamps below your line of sight to remind your body the sun has already set.

If you like taking things to the extreme or just need something fun to do, you can live by candlelight or put red bulbs in your lamps and keep the neighbors guessing.

A few more things:

• Light coming through windows gets scattered by the glass. There is no substitute for going outside!

• It’s ok to use a little light to go to the bathroom at night, you don’t have to sleep blindfolded in a cave to benefit from darkness

• Most phones have a night setting that blocks blue light (on iPhones go to settings → display and brightness → night shift)

• What you’re doing on your phone is probably more disruptive to your sleep than the light will be. If you want a 99% chance of terrible sleep, open a dating app and start swiping.  

Here’s to a week of brighter days, darker nights, and better health,

Dr. Kelley-Chew
@drkelleychew

I’m a Stanford and Penn-trained MD and health tech founder with over a decade working on health optimization in Silicon Valley. Biohacking for the Rest of Us is my answer to medical elitism – I want all people to have access to cutting-edge science that can dramatically improve their health.

If you’re new, please mark this email as “not spam” so it doesn’t skip your inbox.

If you know someone who might appreciate our little health revolution (or just enjoys a good read over kale), please share.