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How Light and Darkness Affect Sleep



Do you know what the opposite of nocturnal is?


I think we all just know what nocturnal means: Animals that sleep in the day and are awake at night.


It is surprising that we are just nowhere near as familiar with the term ‘diurnal’, this is what we are as humans. We are active during the day and sleep at night.

We are actually in a significant minority in this however as 80% of mammals adapted to sleeping in the day.


We are not quite sure why we evolved this way. However, we do hear the term ‘I am a night owl’ frequently. Biologically, humans are made to do our modern versions of hunting and gathering in the sunlight. Human eyes can not see in the dark very well.

There are some great benefits of being daytime creatures.The main one being something called a circadian rhythm.




Our circadian rhythm is our internal body clock. This prompts us to wake up in the morning and to go to sleep at night. Much like a clock it has lots of moving parts, instead of gears and springs, it has stimuli and hormones.


The main hormones are melatonin and cortisol.






Melatonin is made in the pineal gland in the brain and the role of melatonin is to help the body relax physically and mentally. Melatonin is to help us get to sleep and to stay asleep.


When your Little Darling is getting that amazing 11-12 hours stretch of sleep, it will be the pineal gland that you can be thankful for. However, you can also be thankful for daylight. Exposure to sunlight stimulates the body to produce melatonin. Getting your baby out in the sunlight during the day is not just an old wives tale, it really does help them sleep better at night.


When the sun goes down at night and our eyes stop taking in the light, the brain then responds by releasing the melatonin which was produced during the day. This signals our muscles to start to relax, our brain to slow down and allows us to fall asleep.


In the morning, the blue light from the sun will start to penetrate the skin of our closed eyes which then in turn signals our brain to start to wake up.


The brain helps us get going in the morning by telling our adrenal glands to produce cortisol.




Cortisol has a bad reputation as people will often associate it with stress. This is very true in babies as we have learned that when a baby cries their cortisol levels rise which causes them to be stressed. However, this could be the other way around,It COULD be that they are stressed, so they cry and this spikes their cortisol levels.

Cortisol is a very important hormone. Cortisol regulates metabolism, blood pressure, blood sugar, suppresses inflammation, and regulates the body’s stress response. The main benefit is that it perks us up and keeps us alert during the day.


The intricate dance between light and dark, cortisol and melatonin, awake and asleep, evolved over an incredibly long time, and it worked extremely well until we discovered we could produce artificial light.


Before the invention of electricity and the light bulb we relied on fire, and fire emits very little blue light.


Light bulbs emit a lot of blue light. The other things that emit blue light are .TVs, LED's, computer monitors, iPad's, smartphones and the plethora of screens that flood our eyes daily with blue light.


Sadly, all of the blue light that is surrounding us in the hours that we would normally be enveloped in darkness signals the brain that it’s still daytime will inhibit our ability to release melatonin which makes it harder for us to fall asleep.


I know we can not stop the majority of the blue light that surrounds us but we can turn off the most intense sources of blue light like TV’s and smartphones. I recommend that you do this a few hours before bedtime.




The other tip is to ensure that their bedroom is as dark as it can be. When I say dark, I mean pitch black. On a scale of 1-10.. I am talking about 10!


Blackout blinds can be a game changer, especially if you live somewhere where the days get exceptionally long in the summer.


That is a little bit of knowledge about our circadian rhythms and how it keeps us running daily. Our circadian rhythms just need a little bit of support from us to run at peak performance.


If you work with your circadian rhythm instead of resisting it, I guarantee, you will start seeing, and feeling, the results immediately.


Do you need more help with early morning wake ups? I have a Early Wake up guide that will help.





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