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Sleep Science



The answer, it seems, is more clocks than can be found in Grand Central Station.  I am referring to the circadian clocks that reside within all of us.  Scientific studies have uncovered that many of our cyclical daily processes and functions are governed not by one master internal clock, but by numerous interconnected circadian clocks throughout our bodies.   These findings offer great insight as to how we should plan our daily activities, and even when we should eat.  Aligning with our bodies’ natural processes can directly impact the quality of sleep we get.

The Master Circadian Clock

Almost all animals and plants are attuned to, or follow a circadian rhythm – essentially a 24-hour natural cycle that drives processes such as sleep/wake schedule, insulin secretion, and digestive activity.  The word “circadian” comes from the Latin words “circa”, meaning around, and “diem”, meaning day.   Humans have a master circadian clock formed from 20,000 nerve cells that are gathered into a tiny structure called the suprachiasmatic nucleus, or SCN.   It is located in the hypothalamus region of our brain, and when functioning properly, keeps pretty darn good time.

The SCN receives light/dark input from the optic nerve tract, providing its primary sync-up mechanism to the outside world.  Interestingly, research has shown that there is some slight variation of individual circadian rhythms, but only very slight – the mean average is something like 24.2 hours, just a smidge longer than the earth’s daily rotation.    If you know someone who is a true early morning person, or a night owl, it is possibly related to how their individual circadian rhythm is coded.  They are still on a very regular 24-hour clock, but as much as 20% of people may have up to a two hour shift (either earlier or later) in the daily rhythm of their clock.

Related to natural, nourishing sleep (the focus of this blog), the master circadian clock – the SCN – drives our sleep cycle by sending signals at the right time to the pineal gland (also in the brain) to release melatonin into our system.  Melatonin is the natural hormone that causes drowsiness and lowers body temperature.   Thanks to the master circadian clock (SCN), our melatonin production increases in the evening (as light diminishes), peaks in the middle of the night around 2-4am, and drops down in the morning hours (as daylight returns).   Peak melatonin production takes place around the same time that REM sleep is occurring.  Some studies have indicated that melatonin increases the duration of REM sleep.

All of this happens day in and day out like, well…clockwork.  Pretty amazing.

Circadian Clocks Exist Throughout Our Bodies

Here’s where the plot thickens.   Additional discoveries indicate that there is not just a master circadian clock in our bodies, but many localized, specialized circadian clocks throughout our bodies.   The SCN retains the macro role of symphony conductor, but all the other clocks manage micro specialized cycles and chime in for their appointed timed cycle.   The heart, pancreas, liver, lungs, kidneys, skin and lymph nodes have built in micro circadian clocks that work in conjunction with the master SCN.   Circadian clocks have been discovered to reside in tissue cells throughout the intestine, too. (Numerous detailed studies about circadian clocks are published on the National Institutes of Health site.)

As an example, during the day, a specialized circadian clock within the pancreas signals the organ to increase its production of insulin to help control blood sugar levels during the periods when we are traditionally consuming the most food.  At night, insulin production slows down significantly.   Studies among shift workers have found heightened levels of Type II diabetes, among other health issues.  It is possible that a contributing factor is because shift workers are eating during the times when the pancreas’ circadian clock is telling it to shut down insulin production.

Lessons Learned from our Natural Programming

Circadian clocks are result of 1,000s of years of human evolution with one very consistent factor – the Earth’s clockwork rotation and rise and fall of the sun.  Scientific studies are now enlightening us that our bodies’ systems are engineered and programmed to perform around that same 24-hour cycle in some truly remarkable ways.   That’s a lot of natural programing to respect and appreciate – and to listen to.

To achieve the most nourishing, healthful sleep possible, here are several thoughts to consider to better align with the symphony of circadian clocks in our bodies:

  1. Try to follow somewhat regular sleeping times.  When possible, go bed and wake up around the same times each day to allow your own sleep cycle and all the other circadian cycles triggered by nighttime, to follow their natural rhythms.
  2. Take control of the light levels in your bedroom / sleep environment. Our sleep / wake cycle is synced up very closely to light level, so the more you can keep light out of your bedroom at night, the less disruption will occur with your natural melatonin production process over time.  I have not seen any studies about potential impact of light emitted from flickering TV screens or cell phones during the night on the sleep / wake circadian cycle, but common sense suggests there might be an impact beyond the obvious issue of these devices introducing topics to keep you awake in the middle of the night.
  3. Align eating times with natural body clock rhythm. Beyond the sleep / wake cycle, our bodies appear to be programmed to consume and digest food during the day, and much less so during nighttime hours.  This is a really hard one for me.  What’s better than a nice glass of wine and maybe even a few cookies as you close out a day?  Maybe the circadian systems of the wonderful citizens of Barcelona have evolved over time to help them deal with their famously late meals, but for the rest of us, late dinners and treats appear to be a bad idea.

It seems that by recognizing and paying greater attention to the natural rhythms of our bodies, we have a chance to achieve more nourishing, replenishing sleep.  Whole sleep, whole you.


Article by Jim Huffstetler    (July 29, 2018)

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