The circadian rhythm is a large and complicated subject that overlaps many areas of biology. It is of fundamental importance for our health because our internal clocks control about every other bodily function.

Therefore, the whole field dealing with optimization is also called circadian health or chronobiology. With simple tips, you can solve the causes that lie at the root of the insomnia-ridden, blue-light toxic modern world.

In this post, we’ll work our way from the ground up on how circadian rhythm works, what all the clocks are about, and what’s most important to practically optimize your chronobiology, with far-reaching consequences. To do this, we’ll stay close to the literature1A killer resource is Stanford professor Andrew Huberman’s HubermanLab podcast, episodes 1-5 are all about sleep and chronobiology. and look at the mechanisms of how it works, how:

  • The importance & adaptations to daylight of all life.
  • How the circadian clocks are set
  • What sets the circadian rhythm & can upset it

Sounds like a good travel plan, doesn’t it? So, let’s go!

Chronobiology: All Life depends on Sunlight

This is not an exaggeration. All living things align their entire biology with sunlight.

Some creatures have literal holes in their heads to let light information to their control centers, like various single-celled organisms. Others grew their brains outward, as we did with the optic nerve. Eyes have actually evolved ~40 times separately over the course of life’s evolution, again underscoring its importance.

Daylight has always been there and always will be. It regulates our circadian rhythm
Light has always been there and always will be.

And it makes sense, because light was always there and always will be. When the sun dies, so will all life. Fortunately, it’s still a few billion years away!

What is Light? It is Quantum Energy!

Let’s think about what light is. It is energy on the quantum scale. Energy carrying electromagnetic information.

Tiny photons with different wavelengths and a spectrum of energy, all wildly mixed together. This includes visible light, but also all other types of electromagnetic radiation. Daylight is therefore literally a colorful potpourri.2Ionizing radiation such as X-rays or gamma rays are also included here, as are non-ionizing types such as microwaves, radio waves, UV light and magnetic waves. The novel gravitational waves are also included here.
For all life energy is of fundamental importance and the basis of all being. Without energy, no life. Life is an energy-generating process that resists entropy.

The cool thing here is the 24h rhythm of the earth around the sun. Life has become accustomed to it, and as experiments show, it is hardwired into us. This adaptation to each new day length, day after day, is taken care of by your circadian rhythm. Light is the messenger. For humans, the circadian rhythm influences literally every bodily process – from sleep & wakefulness, to body temperature, hormones, libido and immune defense.

The Circadian Rhythm explained simply

To ensure this closely timed coordination, your body uses various clocks in your body. Metaphorical clocks, of course – they are neurological systems that function in this way to keep your body in tune with the daylight input you receive.

The most important clock is in the brain, but interestingly, many cells have their own clocks to keep themselves in time.

Differet circadian Clokcs measure the Time of the Day

The main Clock sits in your Brain – the SCN

The most important clock sits in your head and consists of three things:

  • Your eyes and the optic nerve
  • An area of the brain called the suprachiasmatic nucleus (SCN)

But let’s start where light first meets human. Eyes & Skin. The skin is an important circadian and hormone producing organ, but we will deal for now with the eyes.
Imagine we are tracking a photon. First, it enters your eyes through the lens and falls directly onto the retina. In the retina, different light-sensitive cells are located. They become active depending on the wavelength of the entering light. Some are tuned to blue light, others take care of other aspects of vision such as day & night vision. These cells talk to many brain regions, this exchange of information happens via the massive optic nerve. But the region we’re interested in is the hypothalamus, of which the suprachiasmatic nucleus is a part.

So let’s take a closer look at these two terms:

Hirnanatomie 101. SCN, Hypothalamus, und Zirbeldrüse.
Brain Anatomy 101
  • The Suprachiasmatic nucleus (SCN) means nothing else than ‘a structure located under the crossing of the optic nerves’.3Your optic nerves cross each other. For example, the vision of your right eye goes into your left brain. This crossing is called the ‘optic chiasm.’
  • Hypothalamus means ‘below the chamber’. It is an important part of the brain that connects the central nervous system with the endocrine system – mind with body, if you will.
  • The chamber here is another important brain area called the Thalamus.

The SCN’s Function & photosensitive Ganglion Cells

As you can see, all these technical names mostly tell you where something is located in the brain, more rarely what they do or what they look like. So for example the word ‘Amygdala = Almond’, or ‘Sella Turcica = Turk’s saddle’.
But back to our photon. After hitting the retina, it activates certain cells. These cells are called ipRGCs or intrinsic photosensitive retinal ganglion cells. Now if that’s not an appropriate case for an abbreviation! These cells send a signal directly to the SCN – and this is where it gets really exciting:

  • Cells in the front part of the SCN start to activate certain genes, the so-called CLOCK genes. Creative name!
  • These cells also synchronize other clocks in the body with the master clock, the SCN.
  • The SCN in turn sends this processed information to its master, the hypothalamus, but also to the brain’s hormone interfaces, the pineal and pituitary glands. The pineal gland modulates body temperature, cortisol levels, and melatonin production.
  • Cells in the posterior part of the SCN even function without light input and still manage to maintain the 24h rhythm. This is especially interesting for hibernators.

All right, so far so good. I hope this was understandable so far. Remember that the SCN is the master clock of the body, which all others are inferior to. Light is the direct input that must reset the SCN every day. A multitude of body functions depend on it.

Tissue-specific Clocks

Many organs have their own clock systems that control their activity. You can think of these clocks as team leaders of the ‘liver’ department. While the Supervisory Board is the SCN and calls the shots, the tissue-specific clocks operate in their own areas.4Circadian clocks: Body parts respond to day and night independently from brain, studies show.

The fascinating thing about these clocks is that they are directly influenced by light – even without input from the SCN. So if you were to shine light directly on your liver, it would respond. Happens rarely, of course, because it’s deep in the body. But for organs like the skin, and organs close to the skin, this is enormously important. Certain light frequencies such as infrared and near-infrared can penetrate the body, up to 30cm deep, and thus directly affect the organ systems. Thus the skin is a huge hormonal organ and light activates various processes. What we also know is that light directly stimulates the mitochondria – especially complex IV of the respiratory chain, where mitochondrial water is produced.5Mitochondrial cytochrome c oxidase is not the primary acceptor for near infrared light—it is mitochondrial bound water: the principles of low-level light therapy + Photobiomodulation Directly Benefits Primary Neurons Functionally Inactivated by Toxins: ROLE OF CYTOCHROME c OXIDASE

How the Circadian Rhythm controls the Sleep-Wake Rhythm

As we have already seen, the feelers of these clocks span many systems, so such a simple input as ‘light’ has far-reaching effects. The following are the main players in the sleep/wake cycle and are directly determined by the circadian rhythm. Thus, light has a direct influence on them.

Melatonin: so much more than solely a Sleep Signal

Melatonin’s arguably most important role is in initiating the sleep cascade. Sleep cascade because like a string of waterfalls, many biological steps must occur for you to successfully fall asleep.

Blue light6In fact, all types of light inhibit melatonin if they are strong enough. Blue light is by far the most potent. Inhibits the release of melatonin directly and very potently – so potent that looking at a light source at night when you get up sends your body levels plummeting. It is released as soon as the amount of blue light entering your eye decreases. That’s why sleep hygiene is so essential in the age of modern technology.
During sleep, melatonin levels are high, here especially it exerts its other effects, such as:

  • Re-setting and synchronization of clocks in the body
  • Strong antioxidant effects, especially on the brain
  • Involved in blood pressure regulation and immune function
  • influences bone density, body weight and libido
  • also important for early embryonic development

These effects happen through many mechanisms, in the brain melatonin has 3 receptors. 7Melatonin: Pharmacology, Functions and Therapeutic Benefits It is largely formed in the pineal gland, which sits deep in the center of the brain and interestingly is associated with fluorogenic calcifications.

Adenosine: tells your Body about its own Fatigue

Another factor that induces sleep is high levels of adenosine. So, what is adenosine?

Adenosine is a substance that is naturally produced in cells that do a lot of work – most commonly in nerve cells. It is a sign of cellular fatigue. The longer nerve cells have to work – in total and at a stretch – the more tired they become and the more adenosine they accumulate.
It gets exciting when we look at its recycling. Adenosine is purged during sleep. The perpetual increase of adenosine throughout the day is called ‘sleep pressure8Adenosine and Sleep‘ and is why you need to sleep at some point – sleep or die. Literally.

As a Fun Fact: Caffeine partially shatters this mechanism because it blocks adenosine receptors. So your body doesn’t realize it has high adenosine levels or that it’s tired. Your body thinks it has energy, even though the reality is otherwise. Caffeine habituation is the fact that your body simply builds up more of the receptors, so you need more caffeine for the same effect.

What else influences the Sleep-Wake Rhythm?

Melatonin & Adenosine are the two main drivers. Both are under the influence of daylight. But there are other factors besides these, you can find a few here:

  • Your body temperature
  • Parasympathetic activity
  • Physical activity
  • Your hormone status

Let’s take a look at all of them in turn:

Your Body’s Temperature

We have had a long time as a race to adapt our biology to the circadian rhythm of the Earth.
We had a long time in the course of evolution to adapt to the light.

Your body temperature decreases and increases in a cyclically regulated manner:

  • Warm means you are generally more active
  • Cold means your body is more tired

Your temperature maximum falls in the afternoon, the minimum in the deepest sleep phases around midnight. These values are exactly dependent on your bedtime. You can manipulate these values through showers, baths and the temperature in your bedroom.
Cold rooms & warm baths for example help your body to cool down for sleep.

Parasympathetic Tonus

Parasympathetic activity is the nerdy term for being relaxed.

Going to bed relaxed helps you fall asleep – everyone probably knows the situation when your head won’t shut up or you actively worry all too well in bed. Sleep impossible.
Things like breathing training, journal writing, reading, or meditation can help increase parasympathetic tone here.

Sympathetic Activation

Exercise, for example, is a direct sympathetic stimulus. Thus, exercise, if strenuous, is directly opposed to relaxation. Also, serious exercise increases various hormones like cortisol, which also affect your internal clocks. But the same goes for anything else that fires up the sympathetic nervous system – ice baths, coffee, stress, or crack.
For example, you might exercise early in the morning if you want to set your circadian rhythm and thus your rise time earlier. Likewise, evening exercise makes it harder for you to get to bed.

Hormonal Balance

Of course, your hormones as the body’s messenger substances also have an influence on sleep. High adrenaline, noradrenaline and cortisol are anything but conducive to sleep. You can take advantage of this if you want to avoid sleep or push it back – ice baths or workouts help. Sleep promoting on the other hand is the hormone melatonin as we have seen, in the brain it is the neurotransmitters GABA, glycine and serotonin.9GABA mechanisms and sleep

Interestingly, of course, a sharp increase in cortisol happens after getting up. This must occur and is intentional. The natural wake-up call. It is coupled to early morning sunlight. Therefore, early daylight, within the first hour after getting up, directly into the eyes for 10-30min is an absolute must.

Circadian Health in the modern World

The Issue with Artificial Light

Artificial light is a fucking nightmare. There’s no way to say it differently.

It messes up our circadian rhythm because it inhibits melatonin. Throughout the day, artificial light also doesn’t provide the benefits that natural light does, as it is far weaker and doesn’t contain the entire spectrum. Not only that the flicker and AC current also create EMF and do their harm on even more levels.
This leads to a myriad of other health problems that come with blue light toxicity.

Do better and optimize your lighting environment with human biology in mind:

  • Turn off all artificial light in the evening, 1-2h before you go to sleep
  • Turn off overhead lights in the early evening
  • Use candles or red lights when it gets dark
  • Use blue light blocking apps, such as Iris, or blue light glasses during the day & night
  • Open a window when indoors or sit outdoors while working behind screens.

Get as much Sunlight as possible

One of the most powerful habits to build for your overall health is morning & evening sunlight for 10-30 minutes. The best thing is that you can combine other habits with it, like walking, earthing, or reading on the balcony.

Seeing the Sunrise

This timed daylight exposure acts as the first circadian anchor for your body.

Early in the day, your eyes are sensitive to daylight. Therefore you should give your body around 10-30 minutes. In the morning it will lead to a natural rise in cortisol. Plus, morning sunlight is higher in red light wavelengths, which come with their own potent benefits.

Watching the Sunset

Late evening daylight is the second circadian anchor.

It gives your body a span of light and a beginning and end. Depending on the season, this may be earlier or later. By providing this information your body will know at which time of the year and point of the day you are – and for example ramp up your libido during longer days with lots of light. Like the sunrise, the sunset is also stronger in red light.

Daylight as well as in the sunset have strong effects on your circadian rhythm.
There’s a reason sunsets are so addictive…

Get sufficient Light throughout the Day

Between sunrise and sunset, you should get as much sunlight in your eyes and on your skin as possible.

The reason is the high amounts of UV radiation. You will only get it throughout the times of the day when the sun stands at a high angle. UV-light is a strong signal and the major frequency to charge your body’s semiconductor.

A good target is a total of 2h of daylight. Optimally this means 30min in the morning, 1h at noon and 30min in the evening. More is better, as long as you can do it safely. Of course, don’t act stupid and burn yourself or stare directly at the sun.
You should also avoid sunglasses and sunscreens. The former prevents light from entering your eyes and working its magic, the latter is packed with toxins and prevents light from interacting with your skin. The same also applies to windows, as they act as a filter. They are made to filter red light and therefore bastardize the natural spectrum of daylight.

In summary:

  • 10-30min daylight in the early morning – best 30-60min after getting up.
  • 10-30min of daylight in the late evening – best 1-2h before bedtime.
  • Total 2h of daylight per day. More is better, but don’t act stupid.
    • Don’t wear sunglasses or sunscreen.
    • Avoid sunlight that hurts your eyes (e.g. when skiing). If light hurts, look away or wear ski goggles.

Eat sufficient Vitamin A

Vitamin A is THE sunshine vitamin, not vitamin D.

Vitamin A refers to the retinols. Retinols were the first vitamin that life created because the substance can interact with sunlight quantum mechanically.

In our eyes, vitamin A is needed to convert incident light energy into electrical nerve signals. This creates color vision, as well as light and dark sight. Without vitamin A, meaning true retinol, there is no vision. Followingly poor vision = poor circadian function, as everything is dependent on the impulse of incoming light.
Additionally, Vitamin A shares the transporter and receptors with Vitamin D. Both fat-soluble vitamins exist in a balance with many interactions. You can learn more about this in my eBook.

You can only option retinol from offal, especially liver & kidneys. It is a true zoonutrient. If you don’t eat offal regularly, you do not get sufficient Vitamin A. There is NO vitamin A in plants. Unfortunatly and to the confusion of many, Beta-Carotene is referred to as Provitamin A and often labeled in units of Vitamin A equivalent. Indeed your body can convert Beta-Carotene to Vitamin A, yet the big question is – how much and into which forms?
Briefly sais the conversation is poor. Don’t try to get your Vitamin A from plants, and instead eat offal regularly.10

Develop an insanely strong circadian Rhythm

Probably the biggest problem these days is changing sleep-wake times. Getting up early during the week and staying up late on weekends. This puts you in a jetlag-like state of circadian dysfunction week after week. Avoiding that is one of the most important health decisions you can make for yourself.

So go to bed and get up at the same time each day.

There should be no exceptions, except the odd day. One night a month will surely do no harm, every weekend one night will for sure. What you do 90% of the time is what counts.
With this intervention, you will be able to save yourself from many problems down the road. You will also set your circadian rhythm, coupled with morning and evening light. Your body will provide you with more energy, knowing when you are hungry and tired, or awake and active. You’ll have the energy to do what you want.

Believe me when I tell you that these two things, regular sleep-wake cycle and sufficient daylight, are the most powerful health interventions. You will quickly notice it.

Therefore, be fanatical,

This signature signs everyone of my posts on Ancestrally Healthy.

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