Circadian Rhythms in Humans: Causes of Disorders and Simple Ways to Restore Them


The circadian rhythm is a biological process that has a significant effect on metabolism, the work of internal organs, and the state of human health.

The concept of circadian rhythm was introduced into the lexicon by the American scientist Franz Halberg, the founder of such a field of science as chronobiology. He did it back in 1969. Having carried out a simple experiment, he found that a person isolated from the external environment and focusing only on their own well-being maintains a cycle of sleep and wakefulness equal to about 25 hours. What do we see? Almost complete correspondence with the daily period.



Last Updated: October 3, 2022 (A few hours ago…)


Circadian Rhythms in Humans: Causes of Disorders and Simple Ways to Restore Them



… indeed we are all, and very often, almost like madmen, with the only small difference that the “sick” are a little more maddened than we are, so here it is necessary to distinguish a line. And it is true that there is almost no harmonious person at all; for tens, and maybe many hundreds of thousands, one by one is found, and even then in rather weak specimens …

— Fedor Dostoevsky —


More recently, in 2017, three American scientists (Hall, Rossbash, Young) received the Nobel Prize in Medicine for their discovery of the molecular mechanisms that govern circadian rhythm.


Scientists have found that the circadian program is regulated not only at the central, but also at the peripheral level. The central control point of the main system is the nucleus of the hypothalamus, however, most organs and tissues are able to synchronize their biological clock in an isolated mode. If we draw analogies, then we can compare such a system with a clockwork. Scientists have yet to figure out the intricacies of this interaction.

Our cell is a small biochemical laboratory controlled by genetically stored information. All processes here also follow a strictly regulated scenario, and the timing of their launch is regulated by certain proteins. For example, the NAD + / SIRT1 genes (clock genes) also reduce the activity of mitochondria during periods of low activity, and they are cellular “batteries”. There is a lack of energy in the cell, and the metabolism slows down. As you can imagine, the constant malfunctioning of cells easily leads to the development of diseases such as obesity.

Circadian Rhythms in Humans: Causes of Disorders and Simple Ways to Restore Them

A person does not live in a vacuum, his body and brain are constantly exposed to external influences, and not always favorable. This was perfectly understood by the German biologist Jurgen Aschoff, and in his scientific work he was looking for external stimuli that negatively affect circadian rhythms. He coined the term zeitgeber (if translated from German, it turns out ‘giving time’), referring to them external factors with which our body is synchronized. A kind of precise time service for cells.

You can make a small list of the main synchronizers mentioned by Aschoff with which circadian rhythms are associated:


  1. light (change of day and night);
  2. temperature;
  3. the use of drugs;
  4. food intake regime;
  5. Atmosphere pressure;
  6. rest regimen.

Synchronizers of circadian rhythms Ashoff. Illustration by Anna Kibalnikova

There are many factors affecting the biological rhythm, but the main ones can be considered the observance of the sleep and wakefulness regime, as well as food preferences.

For example, a signal about the onset of darkness passes through the retina and optic nerve and enters the hypothalamus. As a result, the hormone melatonin gradually begins to be produced, preparing the body for sleep. This is perhaps the simplest and most illustrative example of how synchronizers work.


Table of Contents


Daily circadian rhythms by the hour

Trying to generalize the information collected by scientists, you can divide the day into conditional intervals. This scheme is surprisingly similar to the ancient Chinese scheme of the movement of qi energy, when at a certain time this or that organ manifests its activity. Ancient Chinese medicine is largely built on the basis of this knowledge. The following table of human circadian rhythms by hour will help our reader better understand and listen to his own body.

Circadian Rhythms in Humans: Causes of Disorders and Simple Ways to Restore Them

Daily rhythms by the hour. Illustration by Anna Kibalnikova

  • 5:00 am – 7:00 am. Time of activation of the large intestine, a sharp increase in blood pressure and activation of other body functions.
  • 7:00 am – 9:00 am. Activating the stomach, stopping the production of the hormone melatonin, ideal time for breakfast and a walk.
  • 9: 00-11: 00. The brain is maximally attuned to work, increased alertness and concentration.
  • 11: 00-13: 00. During this period of time, blood circulation works perfectly; main meal.
  • 13: 00-15: 00. Total energy is dropping, ideal time to digest food, get some rest.
  • 15: 00-17: 00. Energy recovery, active work and study.
  • 17: 00-19: 00. During this period of the day, the maximum pressure and maximum body temperature are observed. Possible last light meal of the day. The bone marrow is restored.
  • 19: 00-21: 00. Decrease in the activity of all body systems, preparation for sleep.
  • 21: 00-23: 00. At the beginning of the period, melatonin begins to be produced. Cell regeneration of the whole organism begins.
  • 23: 00–01: 00. Sleep, growth hormone is produced, intestinal motility is suppressed.
  • 01: 00–03: 00. Deep dream. The liver cells are restored and the body is cleansed.
  • 03: 00–05: 00. Deep dream. Lung cells are renewed. Lowest body temperature.

Almost every person in his life has encountered a failure in the work of biorhythms, and some live in a constant failure. A good example is a flight to a different time zone. With the increase in the pace of life, this becomes a problem for people who are often forced to move from one region to another. Professional athletes in their training pay great attention to correct recovery, including adaptation when changing time zones.

Police, doctors, firefighters, transportation workers and many more – there are more and more people in the world who work on floating unstable schedules. And if you are a representative of just such a profession, then please take a closer look at your health. It is possible that your poor health is a consequence of an imbalance. Now let’s talk a little about ways to eliminate circadian rhythm disorders.



Restoring circadian rhythms: easy ways

So, are you feeling tired, insomnia, fatigued, or just want to experiment on yourself? The first thing to do is to establish a daily routine. If you cannot afford to go to bed at 10 pm and get up at 5 am, which would be completely consistent with biological rhythms, then at least try to go to bed and get up at the same time.

The time from 10 pm to 4 am can be considered ideal for sleeping. At this time, the production of melatonin is at its maximum, and cell regeneration is more active.

It is important to completely exclude light from entering the bedroom at night . According to research from the US Institute for Behavioral Medicine, even 5 lux lighting (daylight, by comparison, 50,000 lux) can reduce the production of melatonin and invigorate the brain. Also, stop using your phone and computer at least two hours before bed. Go to bed in a cool room with a temperature of about 18 degrees.

Circadian Rhythms in Humans: Causes of Disorders and Simple Ways to Restore Them


The second important tip for restoring circadian rhythms is to avoid eating 3 hours before bed . Hormones, which are produced during digestion, increase the body’s activity. In addition, everything that does not have time to digest before bedtime will remain in this state until the morning. In such a situation, one cannot speak of a full-fledged night’s rest. If you cannot resist evening snacks, then you should think about and reconsider your eating habits: it is possible that you simply do not have enough calories in your daily diet.

Not only poor diet, but also exercise can stimulate brain function and cause circadian rhythm disruption in the evening. All physical activity should end no later than 17 hours . An hour’s workout in the morning is ideal for your well-being.

It is very important for the body to be able to be in direct sunlight for some time during the day . Our body and our brain get a great external stimulus – the start of the day. But man is a hardy creature and adapts to life in any conditions, for example, in the Far North. In these harsh regions, the sun sometimes does not come out over the horizon at all. If you are a resident of such a region, then you should use the brightest artificial lighting during the daytime in order to somehow make up for the lack of sunlight.

Research into human circadian rhythms has a lot more to tell. Not much research has been done in this branch of biology, and it has the potential to bring many more useful discoveries. Who knows, maybe it is only thanks to the alignment of internal and external rhythms that we, as a species, can begin to lead a healthier life in all planes.

Leave a Comment

%d bloggers like this: