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Circadian Rhythm

Did you know that the Nobel Prize in Physiology and Medicine 2017 was awarded to Jeffrey C. Hall, Michael Rosbash and Michael W. Young for their work on Circadian Biology? While this is a very hot topic at the moment, it is not something completely new to science.

Your circadian rhythm is simply a 24-hour internal clock that runs through many body systems. These systems includes hormones, sleep/wake cycles, metabolism and even behaviour. This may explain why you have energy or a lack thereof at a particular time each day. We all know the classic feelings of jet lag we experience when changing time zones, but what if you constantly have a mismatch wherever you live without even getting to jump on an aeroplane?

The implications for this go much deeper than a bad night’s sleep. This chronic release of cortisol leads us to be in an overstressed state and places excessive strain on the adrenal glands. This is just one side effect of an altered circadian rhythm. Some other adverse effects include:

  • Poor concentration
  • Depression
  • Difficulty concentrating
  • Daytime sleepiness
  • Problems falling asleep and staying asleep
  • Problems with school or work performance
  • Decreased cognitive skills
  • Headaches
  • Problems with coordination
  • Digestive problems


It turns out it is very easy in today’s environment to have a circadian rhythm which is out of sync, but what controls our circadian rhythm?

The Master Clock

The suprachiasmatic nucleus (SCN) is situated just above the optic chiasm in a region of the brain called the hypothalamus. Interestingly, the highest concentration of DHA is found in the SCN. Dr Jack Kruse, a neurosurgeon leading the field of Quantum Biology, nicely explains why the SCN is so important in setting the rhythm for our entire body -

“If timing is off, distant signals will also be awry, because they rely on size and distance. Biologic things occur and are applied only as time elapses in proper cycles spatially and temporally. This very same feature is why GPS clocks orbiting the Earth must run faster than clocks on the ground to navigate properly. Atomic clocks are 38 microseconds faster than clocks on the ground. In 38 microseconds, at the speed of light, if this clock difference did not exist, GPS devices on Earth would be off by a factor over ten kilometers of distance on the surface of Earth, rendering them useless for directions. Remember these atomic clocks controlling your Garmin GPS devices are in orbit way above your head and above the Earth. Your SCN works above your peripheral clocks in your body too.”

So how do we confuse our SCN and therefore circadian rhythm?

As it happens, there are many factors which affect our circadian rhythm. These environmental triggers are called zeitgebers (in German, Zeit = time, geber = giver). Some examples include light, temperature, meal timing, and even exercise (an alert reader will notice that the SCN is perfectly situated to interpret our strongest zeitgeber, light).

What is really interesting is that depending on where you live on the globe, some factors may be a stronger zeitgeber for you than for others in different areas.

Let’s explain that with an example: If you are in an environment with weaker light cycles (often winter months), your body will rely more on temperature than light as a zeitgeber. If you are in an environment with stronger light cycles (summer months), your body will rely to a greater degree on light than on temperature as a zeitgeber. This then reasons that during winter, or weak light cycles (when your body relies more on temperature), you would benefit more from cold water immersion (CWI) therapy. *Remember this can also be affected by your latitude’s light cycles (your distance from the equator).

**For the nerds: The master hormone, leptin, regulates how we utilise and control temperature and light signals. Leptin allows the expression of a neuropeptide called vasoactive intestinal peptide (VIP).

VIP sets the circadian clock in our brains to the light cycles. When light cycles aren’t strong (low light cycles), our bodies shift to temperature as the dominant environmental trigger. Leptin induces endothelial nitric oxide synthetase (eNOS) that shuts down the light sensing effects of VIP on the SCN. **


One of the biggest reasons we have out of sync circadian rhythms is because of our light environment. This is where blue light comes in….

Blue light and our hormones

Our sleep/wake cycle is controlled very well by the balance between cortisol (stress hormone) and melatonin (sleep hormone). These two hormones should follow a daily rhythm where cortisol peaks in the morning and melatonin peaks at night.

Our bodies have developed a very clever mechanism over many years for controlling this feedback system.

Before modern technology, our bodies would only be exposed to blue light from the sun in the morning. This would be our cue for the body to release cortisol and wake up. As the day goes by, the sun’s spectrum moves away from the blue wavelengths and closer to the reds in the evening. This lack of blue light exposure is our body’s cue to stop releasing cortisol and start increasing the release of melatonin, preparing us for a good night’s sleep.

Now, over to how we are ruining this….

Modern devices, such as cellphones, laptop screens and even lightbulbs, emit high amounts of blue light. Picture now, it is the late evening and your body should be preparing for sleep. You take out your cellphone or laptop and do an hour's work before bed. What you are effectively doing is telling your body it is mid-morning, while in reality you want to head off to sleep soon. This causes cortisol to increase again and for melatonin production to be suppressed.

It is no wonder we are seeing increasing rates of sleep insomnia (2).

 Hopefully, you now have a greater understanding of what circadian rhythm is and what the implications are when we let our own rhythms become out out of sync.

Our RedPandas are designed specifically to block the unnecessary blue light at the right times of day for an optimal circadian rhythm.



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