To every thing there is a season, and a time to every purpose under the heaven says Ecclesiastes. That also applies to all kinds of processes in the body. In this blog you can read how our internal clock works. We look into environmental influences that can support or disrupt our clock. And if your circadian clock is disturbed, what are the consequences?
In the next blog we will look at how we can influence the circadian clock to support or improve our well-being in this area. How do you reset your clock, how do you synchronize it with the real time? I will give you many practical tips.
Circadian rhythm
We often talk about the day-night rhythm or sleep-wake cycle when we talk about the clock in our body. Sleep is a very important factor in this. If you don't sleep well for one night, or several nights in a row, you will personally experience how important a good night's sleep is. Because sleep deprivation causes fatigue, daytime sleepiness, reduced concentration and memory. Our mood suffers. It also causes changes in our appetite. Poor sleep can make you craving for unhealthy, sweet food.
The internal clock regulates our sleeping and waking, but it does much more. Because in this small example we already see that it affects our mental performance, mood, and digestion, which is under the influence of various hormones.
When we talk about the whole of our internal clock, it is actually better to talk about the circadian rhythm. 'Circa' means 'about' and 'dies' is 'day' in Latin. A rhythm of about a day. This rhythm regulates all kinds of internal processes in the body at a certain moment in a day. And this rhythm of internal processes in the body is influenced by factors from our environment.
On the first day, God created light. If there was day and night, light and darkness, why did God create sun, moon and stars on the fourth day? It is explained in the creation story.
Genesis 1:14-19: “14. And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
15. And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.
16. And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.
17. And God set them in the firmament of the heaven to give light upon the earth,
18. And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.
19. And the evening and the morning were the fourth day.”
Sun, moon and stars are signs of fixed times. Without environmental influences, our day-night rhythm is not exactly 24 hours. Usually it is a little more than 24 hours. Daylight is the most important zeitgeber, the most important signal for the circadian cycle. It helps us set our clocks every day.
Central clock and peripheral clocks
The circadian rhythm regulates all kinds of internal processes in the body at a certain moment in a day. Every organ system, organ, group of cells and almost every cell has its own cycle.
Some examples:
- Digestion is active during the day and at night it comes to rest
- Muscles are at their best in the afternoon
- And most hormones also have their own 'peak time'. Cortisol peaks in the morning
when getting up, melatonin, the sleep hormone, starts in the late afternoon
to rise slowly and has its peak when we go to sleep and in the night.
Our body temperature and blood pressure also have a clock. And all of these peripheral clocks are connected and interact with the central clock in our brain: the suprachiasmatic nucleus. This nucleus is part of the hypothalamus and is located in the center of the head, directly above where the optic nerves cross.
The suprachiasmatic nucleus can be thought of as the conductor of the orchestra, the central clock, to which all peripheral clocks synchronize. This nucleus coordinates all the clocks in our body. And it maintains a rhythm of about 24 hours by itself.
Influencing the internal clock
light
The central clock receives its input from the eyes, among other things. The light from our environment enters the eye through the pupil. It then passes through the lens, which focuses the image, and falls on the retina at the back of the eyeball.
On the retina, in addition to the rods and cones, there are another specific type of nerve cells: light-sensitive ganglion cells. These types of cells do not really help with vision, but they are important for our day-night rhythm. The ganglion cells contain the light-sensitive pigment melanopsin, which responds to blue light. The sunlight has more blue in it in the morning and more red in the evening. These cells therefore register the blue light and the light intensity. They pass this on to the central clock.
This information is important for the suprachiasmatic nucleus. It's a sign that it's daytime. Time to be active. There is now no need to make melatonin (sleep hormone).
The (sun)light that enters the eyes and the use of the AYOlite light therapy glasses work in a similar way.
(Images: Ayo)
seasons and artificial light
Sunlight has a major influence on our circadian rhythm. In the summer the days are long. Do you notice the effect on your sleep or your mood? Compare it to the dark days at the end of the year. Do you notice a difference?
Research shows that people go to sleep a little later in the summer and also sleep a little less long. In winter, on average, we go to bed a little earlier and sleep a little longer. But the difference is not that big, because…
The sun is not our only light source. We all have lamps in our homes. And often several screens: TV, laptop, telephone. These things affect the circadian clock and can cause a disruption of our natural rhythm.
Mealtimes
Besides exposure to light, the times we eat are an important zeitgeber for our circadian rhythm. A large number of metabolic processes related to digestion, energy production and associated hormones have a rhythm of (approximately) 24 hours, which are controlled by our internal clock and food intake.
Mealtimes has been shown to be an overriding zeitgeber in peripheral clocks in the tissues. Irregular times when somebody eats makes those clocks run unevenly. We have already seen that those small clocks are in contact with the central clock. It then finds that these clocks are not synchronized. This results in a disruption of the circadian rhythm and one or more clocks are moved or the amplitude (the wave motion that is made in a day) is lowered.
An expert on the circadian clock stated that for many people, their mouths are open as long as their eyes are open. So that one eats at all times of their waking time. And research shows that this is true for many. This eating pattern is not in line with our natural rhythm and contributes to health problems, obesity and a disruption of the circadian cycle.
Irregular working hours
I worked irregular shifts for 18 years. I continuously switched between early, late and night shifts. You can imagine that disrupts the circadian clock. While it is dark outside, you are active in a lit room, when the sun is shining, you have to sleep and the times at which you eat are also different.
But people who work shifts aren't the only ones who have their circadian rhythm disrupted.
Those who work overtime in the evening, students who spend a long time studying or get up extremely early to finish something also disrupt the rhythm.
And what do you think of the partners of those persons. Meals are delayed in order to eat together. Or you stay up until your partner comes home after a late shift to spend some time together and go over the day, with or without something nice to eat. Then you often don't sleep until after midnight.
Other disturbances of the day-night rhythm at home is for parents of young children. Babies who need to be fed and changed during the night mean that parents, often the mothers, have to wake up several times at night.
Jet lag
Some people regularly have to travel far for their work. Changes in time zones also disrupt our circadian rhythm and is better known as jet lag. In general, people flying to the east are more affected. If you go west, your day will get longer. Because our circadian rhythm is naturally just a little longer than 24 hours, it is easier to adjust. However, when traveling really far, you will notice the effect of different time zones.
There are also people who get jet lag without flying. Those are those who live in a different time zone during the weekend. They sleep late on weekends and also go to bed late. And if they have to go back to school or work during the week, they get up early and go to bed earlier. For their circadian rhythm, it is as if they are flying back and forth between the Netherlands and a number of time zones further away.
Mental problems
Finally, there is an interaction between psychological, psychiatric, neurological (mental) problems and the circadian clock. Think of stress, depression, ADHD, dementia.
There is no doubt that mental problems and a disruption of the circadian rhythm often co-exist. But what is the cause and what is the effect is not always clear.
For example: your sleep can be disturbed because you are in a stressful situation. But on the other hand, a disturbance in your rhythm can also cause stress and lead to a deterioration in mood and even depression.
Live at the right time
In short, our circadian clock is influenced by environmental factors. The most important factors are exposure to light, when we eat and when we are active or asleep. These factors can support or disrupt our natural rhythm.
A disrupted clock
There is increasing evidence that circadian rhythm disruption is associated with a wide range of adverse health consequences. It has a negative impact on almost all present diseases, such as:
- Sleep disorders
- Cancer
- Metabolic disorders, such as diabetes, obesity, metabolic syndrome, reflux,
colitis
- Cardiovascular disease (arrhythmias)
- Allergy and the immune system (inflammatory reactions)
- Issues with the reproductive system
- Rheumatic complaints
- Mood disorders (chronic stress, SAD, depression, anxiety,
irritability)
- Learning and attention disorders.
A study shows that there is a link between the time someone goes to bed and the risk of heart disease. Now bedtime is of course not the only factor that plays a role in this, but it is better for your heart to go to sleep between 10 and 11 PM compared to going to sleep after midnight.
Research has also been done on osteoarthritis. The different tissues in the joints each have their own peripheral clock. The clock that provides the cartilage is disrupted in osteoarthritis. Regularity in the times when someone with osteoarthritis eats and exercises can contribute to the health of their joints.
This overview is not complete, but it does show the seriousness of a disturbed internal clock.
Benefits correctly adjusted clock
So what are the benefits of a circadian rhythm that synchronizes with time?
The risk of (chronic) diseases is reduced and complaints can decrease.
Sleep quality will be better, which will also give more energy and concentration during the day.
Our brains do well on a regular schedule with a properly adjusted clock. Stress decreases and mood improves. Our metabolism also improves.
How do you know if your clock is disrupted?
Signs that your circadian rhythm is disrupted are
- Sleep problems, including falling asleep too early, not being able to sleep, not
being able to sleep through the night or wake up extremely early
- Extreme daytime sleepiness
- Being less alert during the day
- Difficulty concentrating or remembering things
- Bad mood
- Less energy
You may not have these symptoms, but your rhythm can still be not optimal. The app 'My Circadian Clock' can help you gain more insight into your rhythm. The app asks you to keep track of when you sleep, eat, drink and exercise for two weeks. If you want, you can also register your medication, blood pressure, and weight. Also the amount of steps you take in a day. After two weeks you will receive an overview.
After the initial period you can set goals for yourself. For example, a certain time you go to bed and get up or the times you eat. You register this too and you observe how you feel and what changes (improvements, hopefully!) there are in your symptoms or well-being.
Concluding
We have seen that the circadian rhythm is of great importance for our well-being. If the rhythm is out of balance, it can have consequences for health. The three most important factors to influence our internal clock are mealtimes, activity and last but not least light.
Do you want to support your rhythm with light therapy? Then take a look at the AYOlite light therapy glasses in my webshop.
In the next blog you can read how you can reset your circadian rhythm with your lifestyle or how you can support it with a correctly adjusted clock. Would you like to be notified when the next blog comes online? Sign up below for the newsletter.