How light influences your body

Do you remember what they thought you in school abut plants needing oxygen, water and light to grow and bloom? Interesting fact: We humans need all this as well !

There is of course a difference between humans and plants but in the end we do both need light, to function well.

Actually you are much more connected to this planet than you might like it and the more you live with it, the better you function, and the better you function the better your body works and the better your body works.. the better you feel.

Alright now, lets go deeper!

Light → Eyes → Brain 

Remember, there is a clock in your brain, and cells in our eyes, which detect the light outside you? If not, you can read about it here: Why we have to sleep.

You know what? The rhythm continues, and it goes like this:

→ Hormones + nerves → Organ clocks → Cells

So, the big picture actually looks like that: 

And because I already explained about light, our eye cells and the brains clock. The Hormones are next!

 “Which hormones?” 

Lets see: 

Hormones travel through your blood, they regulate your energy, your mood and how your body changes.

“So light comes through my eyes, hits my brain and regulates my hormones?”.
Yes, in a way.
Especially 2 important hormones are affected by how and when we view light. You probably have heard about them ..

Melatonin (your sleep hormone) AND
Cortisol (your wake + stress hormone).

Your eye cells can not only read light! They can also read the frequency of light in the atmosphere. Look, daylight is rich in short wavelengths:

So your eye cells will be like:  

Your Brian spreads this information to your entire body: Lets go! Wake up. Day has arrived, start your tasks everyone! And your body will start to:

• rise alertness
• rise body temperature
• increase cortisol 
• synchronise your internal clock for the day and 
• stop producing melatonin

The stronger the light is you see, the stronger this signals are. So, in very simple words: when you wake up in the middle of the night and you view bright light it will make your body think it is daytime. Through the cortisol increases you feel alert and ready for the day, at the same time your body suppresses the production of melatonin (the hormone which helps you to fall asleep) and thats why, going to bed late or being on your phone at night.. is a problem for your system. I know that your brain KNOWS it is night but love, your body is a machine.. it it made to work that way only your consciousness can not change this.

Now, there are a few crucial things to keep in mind when it comes to light quality: 

Not every blue light triggers the same, there is a massive difference between artificial and natural light.  The strongest indoor light ranges around 100–1,000 lux. Real daylight is about 10,000–100,000 lux. You see, no light is as effective as real sunlight and we are not able to recreate this light artificially. But we can step outside and let it naturally enter our body. 

It is vitally important that you get good quality light communicated to your brain clock in the morning, because without enough quality light your melatonin production will not properly turned off and your for cortisol can not start properly.

“We know based on a lot of evidence that if you don’t get your cortisol and melatonin rhythms timed right there are tremendously bad effects on cardiovascular health, dementia, metabolism, diabetes risk, fertility learning and depression. “

It is important to get quality light from outside, only viewing indoor light through a window will not have the same quality.

That’s often why people feel more tired and less active in winter. It is not because they are “lazy,” but because their eye cells do not get enough natural light their “morning time marker” is missing and therefore their body has a hard time to know what time it is and when to feel tired and when to feel awake.

If you wake up and directly look at your computer or your phone or another artificial light, your eye cells will be activated but not in a good way.

“Many positive things happen when we time our clock right. So, what we want to do is to get outside as soon as possible after waking up. To make sure our body can do his work in the best settings.”

“Alright, got it!, I know how to properly wake my body up and start my system. But what about the turn off? What about sleep? Can I also use light for sleeping?”

Yes. You can!

Therefore let’s quick look back to ~ 1 Million Years ago (1.000.000 years) to understand something important. It was the time when we humans used fire as the only light source next to daylight.
For a long time, fire and daylight were the only light sources we humans had.  Electric light bulbs only established around ~140 years ago and I am now doubting that, we ever got well educated about those.

! INFO:  Fire has about 10 – 100 lx. Remember sunlight? It has 10.000 – 100.000lx.  Lux is how bright your eyes perceive the light, not its color, not the temperature, not the wavelength.

Daylight contains a continuous spectrum of light, so we find a full range of light in it:

Ultraviolet light: < 400nm → Vit D production, Sunburn (invisible)
Blue light: ~400–500 nm → affects alertness
Green light: ~500–570 nm → where eyes are most sensitive
Red light: ~620–700 nm → warm light
Infrared: > 700 nm → heat (invisible)

SunlighT → full range 400–700 nm

Firelight  → mostly 600–700 nm + lots of infrared (>700 nm)

Fire is dominated by long red and infrared wavelengths.

This low frequency, long wavelength light signals the body:
begin to wind down,

• lower alertness,
• reduce cortisol, 
• synchronise the internal clock for sleep
• increase melatonin production
• melatonin release

A beautiful sunset, when the sky turns all red, it is similar to this wavelengths of fire and the cells in your eyes detect it:

Morning →  blue light increases → “Wake up, energy – new day!”
Evening → blue light disappears → “Wind down, calm – sleep!”

The red light from the sunset and sunrise is a transition-signal for your body that a change is happening. Either from sleep to wake, or from wake to sleep.

“The daily rhythm of the sun has always been there and it has always been the same. So our hormone system is exactly constructed towards it. Our whole cycle is linked to the solar cycle.”

Any change, disruptions or misalignments can impair this balance, leading to dis-regulation of hormonal rhythms.

Interesting Side facts:

1. If we would be in complete darkness the cycle would still work. Because after the rise of cortisol (about 12 to14 hours later) melatonin will naturally come up.
2. Most of the night owl people are just not getting enough light during the day! It dictates what time you get tired and sets the foundation of proper sleep! “Maybe your brain just didn’t get enough sunlight.”
3. Blind people (provided they still have eyes) maintain the neurones which set the clock. Its not about seeing the sun, you don’t have to look in the sun directly! This neurones in your eyes which activate this mechanism get activated by the particular wavelength of light that are present in the atmosphere.  They get activated even if they come through cloud cover you don’t necessarily need to see the sun directly to get them startet.
   

Many people only know cortisol as the stress hormone but lets understand what cortisol really does?

Cortisol helps you to feel awake, to wake up, to regulate your bodies temperature, your fluid balance, and it keeps your blood sugar within healthy ranges.

Shortly before you wake up, your cortisol levels rise naturally by up to 50–60% and makes you feel awake, energetic, and alert. It slightly increases blood pressure and body temperature.

Light (especially bright blue light) amplifies this. Therefore watching the sunrise (or when you miss it) good quality sunlight after waking up, helps your body to wake up and get your cortisol rhythm started.

People who tend to wake up after 3-4 hours of sleep feeling wide awake are generally struggling with their cortisol rhythm. 

Cortisol in the morning = good (makes you feel awake)
Cortisol in the evening = bad (disrupts sleep).

BONUS facts:

1. Glucose tolerance peaks during daylight and is lower during the darkness cycle
2. Melatonin drops at sunrise and rises around sunset
3. Cortisol rises just a little later than sunrise
4. Sleep deepens at 1:00am
5. Body temperature rises at 3:00am 
6. Through a single sunrise you can set your clock forward or backward by several hours! (Can be healpful to knwo when traveling between time zones..)