How to boost your energy and easily fall asleep at night (The 10-10-10 Rule)

We spend 87 percent of our time indoors and rarely get exposed to natural light during the day. Towards the night, we then take in plenty of bright, blue light from our devices. In short, we go through "dark days and bright nights".

If you want to boost your energy during the day and easily fall asleep at night, you should do the reverse.

What to do

Get 10 minutes of sunlight into your eyes before 10 am and avoid bright, blue light after 10 pm each day. In short, follow my 10-10-10 rule.

Why it works

Our wakefulness and sleep are controlled by a 24-hour cycle known as the circadian rhythm. As it turns out, light is the most powerful way to set that rhythm (click here for a deep dive). Now, sunlight hitting our eyes sets our circadian rhythm by kicking off a fascinating dance of two chemicals you've probably heard of before: cortisol and melatonin.

First, getting sunlight into your eyes in the morning prompts your system to increase cortisol levels by more than 50 percent. I know what you’re thinking. Cortisol has a bad rep. It’s mainly known as a stress hormone. Yet, we all get a big surge in cortisol at least once over our 24-hour cycle. And this surge is precisely what we need to get going in the morning. In that sense, instead of regarding cortisol as a stress hormone, think of it as a "waking-up hormone".

Second, morning sunlight starts a timer for a second hormone to be released 12 to 14 hours later. That hormone is melatonin. On top of making us sleepy at night, melatonin loathes light. That’s why it's also known as the "hormone of darkness". Yet, late in the day, our brain mistakes any bright, blue light for sunlight. It then thinks that it's daytime and eliminates the melatonin in our system, making it impossible to easily fall asleep.

How to do it

To set up the dance of cortisol and melatonin for boosting your energy during the day and easily falling asleep at night, you need to get your light right. Here’s how.

1) Get 10 minutes of sunlight into your eyes in the morning to avoid “dark days”. Do so before 10 am. You’ll otherwise enter what scientists call the "circadian dead zone". During that part of the day, which lasts until the evening, you won’t be able to set your circadian rhythm. In other words, you’ll miss your chance to switch from night mode to day mode — and get your surge in cortisol late in the day. This, by the way, is not only detrimental to your sleep, but also to your physical and mental health.

2) Adapt the duration to the conditions. It’s not about consciously seeing the sun, but about getting sufficient photons in your eyes. If the sun is out and it's a bright day, go for 5 to 10 minutes. If it's an overcast, dim day, go for at least 10 and up to 20 minutes. As a rule of thumb, aiming for 10 minutes will work fine most days of the year. Last but not least, never look into the sun directly, and know that viewing sunlight through windows, windshields or sunglasses doesn’t work.

3) Avoid bright, blue light after 10 pm to prevent “bright nights”. Use dimmer and lower-angle lights in your home. Unlike bright, higher-angle ones, your brain won’t mistake these for the sun. Also, dim the screens of your devices. iPhones and Android phones have built-in features for doing so in the evening (called Night Shift, Night Mode or Dark Mode). And on your computer, use apps like f.lux to dim your screen automatically.

Getting light right has an outsized effect on your energy and ability to fall asleep at night. You’ll need less caffeine, feel better and focus deeper. So how about following my 10-10-10 rule for three consecutive days?

And if you can think of one person who could benefit from doing the same, please share this post with them.

Until next week,
Christian