As a kid, did you every worry a watermelon might grow inside your stomach after swallowing the seeds?

I did.

Well, I hate to break it to you, this isn't true.

But, there is something else a little stranger inside your body:

A clock.

Ok, not literally a clock.

But, close.

It's called the Suprachiasmatic Nucelus.

It's the time-keeper for your entire body.

And, it happens to be greatly influenced by the 2nd building block for better sleep:

Light.

Table of Contents

1. What makes us fall asleep?

2. A common theme: light

3. 3 action items to exploit light for better sleep

4. Why should I avoid overhead lights at night?

5. Summary

Our Biological Clock: The Suprachiasmatic Nucleus (SCN)

Take your finger (or an imaginary finger) and place it on the bridge of your nose.

You are now pointing at the reason why light affects so much of our life: the Suprachiasmatic Nucleus (SCN).

When someone refers to our inner "biological clock," they are actually talking about the SCN.

The SCN is in charge of controlling our circadian rhythm which, in turn, affects almost every part of our body that responds to different times of day.

This includes hunger timing, melatonin production, cognitive performance, sleep patterns, and so much more.

How Light Affects Your Biological Clock

When light hits our eyes, signals are sent through a brain pathway called the retinohypothalamic tract to the SCN.

The SCN then orchestrates how the rest of our body responds to this signal including:

- Calling on the pineal gland to release melatonin

- Regulation of parts of our nervous system

- Daily behavioral rhythms (feeding, etc.)

Importantly for our sleep, light greatly influences when the pineal gland releases or does not release melatonin.

This is why absence of light is so crucial to our sleep.

And, the presence of light is so crucial to staying awake.

Because, we want high natural melatonin levels at night.

And, low melatonin levels in the morning.

Going against this pattern of light exposure is tricking our brain into thinking something that it shouldn't be.

Your Circadian Rhythm Is Genetic

While light serves a potent role in influencing our circadian rhythm, the SCN's rhythm is rooted in how different genes express themselves.

These genes are called "clock genes" or circadian rhythm genes because of the fundamental role they play in determining our baseline circadian rhythm.

What does this mean for you?

This means even though light greatly influences sleep, at the end of the day, our genes are what determine our baseline feelings of tiredness and wakefulness.

So, if your body naturally prefers going to bed/waking up later than other people, it is most likely because of your genes and not something you should try to fight against.

Tools Using Light for Better Sleep

Follow these steps to leverage light for better sleep:

1) Dim or turn off artificial light levels after sunset

Our body evolved these light-influenced mechanisms because of the sun.

So, it is very wise to match your use of artificial lights to the natural patterns of the sun.

In practice, this means dim artificial lights by at least 50% at night or, even better, just use candlelight or moonlight instead.

2) Turn off overhead lights at night, and instead use lights placed lower in field of vision (lamps, candles)

Just think about it from an evolutionary perspective.

Wouldn't it be useful if our body was more sensitive to light from above (aka sunlight) in telling our body when it's time to go to bed?

Well, scientifically it has actually been proven.

The top half of our field of vision is more sensitive to light than the bottom half.

It's crazy how evolution works.

3) Completely blackout your sleeping environment with a sleep mask or blackout curtains

Any small bit of light can cause you to wake up.

Even if it doesn't cause you to wake up, small lights can interfere with your sleep quality, too.

I would highly recommend getting some sort of light blocker for sleep.

My favorite is a sleep mask because of their portability and price.

4) Get real, natural sunlight in the morning ASAP

Surprisingly, sunlight in the morning is vital for our sleep at night.

Morning sunlight begins our SCN's countdown until sleep.

So, the closer to waking you get sunlight, the sooner that countdown will begin.

Summary

The Suprachiasmatic Nucelus (SCN) sets our body's circadian rhythm, which decides when we feel awake or tired throughout the day.

While our genes determine the SCN's baseline circadian rhythm timing, there's one environmental factor that influences the SCN greatly: light.

Try these four action items to leverage light to get better sleep:

Action Items:

1) Dim artificial lights when the sun sets by 50% or more

2) Turn off overhead lights at night, and instead use lights placed lower in field of vision (lamps, candles)

3) Completely blackout your sleeping environment with a sleep mask or blackout curtains

4) Get natural sunlight in the morning ASAP to start your body's countdown for sleep