Circadian Rhythms Part I—How Your Inner Clock Controls Your Health

Our body’s natural rhythms and our health are being threatened by 24/7 lifestyles, digital devices, cell phones, I pads, lights on our computers and our eating schedules.  How widespread is this problem?  Here are a few facts that will shed light on this question.

  • “More than 27 million Americans—including nurses, firefighters, truck drivers and factory workers—have irregular work schedules” ¹ that may cause health problems due to their altered sleep/wake cycles.
  • Thousands of people regularly fly part way or all the way across the world.  The resultant jet lag causes the body’s clock to be totally out of order leading to fatigue, insomnia, digestive problems, headaches, dizziness as well as various other symptoms.
  • Many people in our world have banished darkness in their sleeping spaces.  They keep the TV, other digital devices and/or lights on in their bedrooms all night long.  In fact, many people cannot sleep or sleep well if it is dark where they sleep.
  • Because of 24/7 lifestyles, social or work schedules, or lights on in their sleeping spaces people are up at odd hours and tend to have irregular eating schedules.


How do all these changes in lifestyle affect our health?  And why would it matter when we sleep, whether we have light on 24/7 or when we eat?  These questions can be answered by defining and discussing the topic of circadian rhythms—our body’s normal daily rhythms.


The word circadian comes from the Latin for “about a day”.² Timing is critical when it comes to discussing the health of the body.  “Scientists have been investigating circadian rhythms for decades, but until recently they did not appreciate how critical these rhythms are to the regulation of nearly every body system.”³


How does it all work?  We function on many levels—anatomical, physiological, biochemical and electrical.  Circadian rhythms create the ebb and flow and the timing of these last three levels.  This accounts for many of the patterns we see in peoples’ bodies.  For example:

  • Fevers being higher at night
  • Teenagers being late risers
  • Late meals making it harder to sleep

All these patterns “are grounded in the daily planetary shift between light and darkness.”⁴


In our bodies it is the suprachiasmatic nucleus (which is in the part of the brain called the hypothalamus) that aligns our bodies with what is going on in the outside world.   It controls our daily rhythms and is called our master clock.


This nucleus is monitoring the light (or lack of light/darkness) that is around us.  For example, if it is dark, the hormone melatonin flows, causing restfulness and the bladder expands to hold more urine so you can sleep more soundly.  On the other hand if the nucleus encounters light around you it will send messages to the body to “start your day”.  This light can be from any source:

  • The sun
  • A light bulb
  • The TV
  • A computer screen
  • A cell phone, iPad or other digital devices (“Digital screens emit the same blue wavelengths found in the morning sunlight.”)⁵


These “start your day” messages can come at any time—1 AM, 2 AM or first thing in the morning.  The timing depends mainly on two major factors.

  • How much light you have around you
  • Whether you have a regular eating schedule during the day (When you eat in the middle of the night this starts the digestive processes that are designed to happen first thing in the morning).  Research shows that it is best to have approximately a 9 to 12-hour eating schedule—most importantly no later than 8:00 PM.


“The suprachiasmatic nucleus functions like an orchestra conductor, keeping time so that the individual rhythms of the heart, liver and other organs can coordinate”.⁶ When this clock is not working properly due to a biological defect (very uncommon), working, socializing or eating late into the night, our bodies no longer have a properly working conductor.  This means that the timing of our bodily functions is off—in other words the clock is NOT working.  It is our daily schedules that affect the clock most of the time.  Any illness or condition can occur when this happens.   


“For years, observational studies have shown that people who work nighttime or rotating shifts are susceptible to much higher rates of obesity and diabetes.”⁷ “Other studies have also shown that a lack of sleep can also cause both these conditions”.⁸


Actually any condition or illness can arise due to misaligned circadian rhythms.  Some examples are high blood pressure, learning and memory problems, immune dysfunction, heart problems or hormonal imbalances.


According to the literature, information about circadian rhythms is seen as old fashioned—your mother’s or your grandmother’s medicine.  Go to sleep at a reasonable hour, eat a good breakfast, lunch and dinner.  Do what you do well.  At the same time be good to yourself and do not push too hard.  Depending on how well you follow these timeless instructions, will have a great deal to do with how healthy you will be.


See Circadian Rhythms Part II—When Your Internal Rhythms are Out-of-Sync, for more fascinating details on this subject.




¹ Out of Sync by Emily Laber-Warren, “Scientific American Mind”, Sept./Oct. 2015, p. 32

² Ibid, p. 33

³ Ibid, p. 33

⁴ Ibid, p. 33

⁵ Ibid, p. 33

⁶ Ibid, p. 35

⁷ Ibid, p. 36

Sleep on It by Robert Stickgold, “Scientific American”, Oct. 2015, p. 55