Circadian Rhythms: What They Are And How To Interpret Them

Did you know that all living beings have a kind of internal biological clock? This mechanism, also known as circadian rhythms, allows us to adapt to our environment throughout the day. And it was not until the 80s that they were studied in depth to understand how it works. And therefore, in this post we are going to explain how to interpret your body’s circadian rhythms. Stay!

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What is the circadian rhythm or biological clock?

The circadian rhythm or biological clock is a molecular mechanism that all living beings have, from plants to animals and humans. Specifically, it is a series of fluctuations that take place in our body on a daily basis to adapt to the environment. 

The body is wise, hence it is essential to lead a healthy lifestyle. And that is why it knows when we need more or less energy, guided by the cycles of sunlight and darkness and the changes of season, with asthenia being so common at certain times of the year.

And how does he do it? Well, our body captures environmental signals through the senses and processes them in the suprachiasmatic nucleus, which is located in the hypothalamus and acts as a central clock. This core is responsible for issuing orders, making our internal parameters synchronize with the environment.

Likewise, you should know that our internal biological clock is made up of three different types of biological rhythms, which are:

  • Circadian rhythms: 24-hour cycles.
  • Infradian rhythms: cycles of more than 24 hours, such as the menstrual cycle.
  • Ultradian rhythms: last less than 24 hours, like sleep cycles.

Circadian rhythms: examples

Energy levels, cortisol levels or blood pressure are some of the parameters that give us a clear indication of the fluctuation of circadian rhythms, since these vary during the day and cyclically to synchronize with the states of sleep and wakefulness.

Hence, in the morning we have more energy to face the whole day, or we have more desire to do things until late in spring and summer, as the hours of sunshine become longer. While at night we are more tired and sleepy, or in autumn and winter we prefer to stay at home watching a movie.

How to know my circadian rhythm

Do you know why you feel more down when autumn begins? Or why are you always hungry at the same time? To interpret your biological rhythm you only need to understand your own body.

As we have been saying, the circadian rhythm in humans is 24 hours. This synchronizes with the earth’s rotation, predicting light and dark cycles and seasonal changes. This allows our metabolic processes to be regulated naturally, hence the production of melatonin increases at night, as well as cortisol levels in the mornings.

Altered circadian rhythm: why does it happen?

The circadian rhythms of living beings usually follow different fluctuation patterns, but these can be unbalanced by different factors. And the consequence of all this is the possible development, in the long term, of pathologies such as cancer, obesity or diabetes.

The human biological clock can be altered by internal factors, such as a mutation. But the truth is that alterations in circadian rhythms usually come from external factors, especially those related to daily habits and lifestyle.

Thus, the circadian rhythm is often altered by changes in sleep patterns, especially in those people who work night shifts. Also due to lack of control in eating, eating high-calorie foods at times that are not normal, or a sedentary lifestyle, since the body is made to move. Some medications, alcohol, caffeine, exposure to screens at night, stress and anxiety are other factors that affect circadian cycles.

Without a doubt, a clear example of an altered circadian rhythm is jet lag, since the change in time zone causes a temporary imbalance in the body’s functions, impacting sleep and hunger. And the symptoms of this phenomenon end when our body synchronizes with the new light/dark cycle again

How circadian rhythms affect different areas of our body

Circadian rhythm and organs

Do you know that your liver doesn’t work the same in the morning as it does at night? Organs also have their own biological rhythm, just like cells and tissues. And, depending on the time of day, some proteins or others are activated, which communicate with the rest of the body’s circadian rhythms, including those of each organ.

So, following the example of the liver, thanks to human evolution and the development of our biological clock, its molecular mechanism understands that at night it does not have to metabolize anything because we do not eat food, while during the day, in a few hours Specifically, the liver is prepared to metabolize what we eat. And the same thing happens with the pancreas, which is more active during the day because it knows that it has to produce enough insulin to regulate blood sugar. Hence, then, the importance of maintaining a routine that is in line with the day and night light cycle.

Circadian rhythm and hormones

Circadian rhythms also have a direct influence on the hormones we produce, which differ between the state of sleep and wakefulness.

With a lack of light, biological rhythms activate the production of melatonin and serotonin, hormones that induce sleep, tranquility and well-being, as well as growth hormone and the hormone that stimulates the thyroid. Rhythms related to hunger (ghrelin hormone) and satiety (leptin hormone) are also regulated.

On the other hand, during the day, the biological clock activates the production of adrenaline, cortisol and norepinephrine, which causes us to have more energy, concentration and precision when carrying out daily tasks.

Circadian rhythm and cortisol

You feel better when you expose yourself to the sun for a while, especially in winter, right? Well, believe it or not, UVA rays, cortisol and the circadian rhythm are closely related. And the sun’s rays help reduce cortisol levels, reducing its production and increasing serotonin levels, the hormone of happiness and well-being.

How can a circadian rhythm get out of sync?

Exposure to Artificial Light

Modern lifestyles often involve prolonged exposure to artificial light, especially from electronic devices such as smartphones, tablets, and computers. The blue light emitted by these devices can suppress the production of melatonin, a hormone responsible for regulating sleep. Excessive exposure to artificial light, especially in the evening, can trick the brain into thinking it’s still daytime, disrupting the circadian rhythm.

Irregular Sleep Patterns

Inconsistent sleep patterns, such as frequent changes in bedtime or wake-up time, can throw the circadian rhythm out of sync. Shift work, jet lag, and irregular sleep schedules can confuse the body’s internal clock, making it difficult for individuals to maintain a stable circadian rhythm. The body may struggle to adjust to changing sleep-wake cycles, leading to disruptions in the natural circadian process.

Jet Lag and Time Zone Changes

Traveling across multiple time zones can lead to jet lag, a temporary misalignment of the circadian rhythm with the local time. The abrupt change in the day-night cycle confuses the body, causing symptoms like fatigue, insomnia, and irritability. It often takes time for the circadian rhythm to adjust to the new time zone, leading to a period of discomfort and sleep disturbances.

Poor Sleep Hygiene

Inadequate sleep hygiene practices can contribute to circadian rhythm disruptions. Factors such as an uncomfortable sleep environment, excessive noise, or irregular bedtime routines can hinder the body’s ability to maintain a healthy sleep-wake cycle. Establishing a consistent and relaxing bedtime routine, optimizing the sleep environment, and avoiding stimulants before bedtime are crucial for supporting a well-regulated circadian rhythm.

Stress and Mental Health

High levels of stress, anxiety, and mental health disorders can impact the circadian rhythm. Stress hormones, such as cortisol, play a role in regulating the sleep-wake cycle, and an imbalance in these hormones can disrupt the circadian rhythm. Chronic stress or mental health conditions like depression can lead to irregular sleep patterns, making it challenging to maintain a synchronized circadian rhythm.

Inadequate Exposure to Natural Light

Insufficient exposure to natural light during the day can also contribute to circadian rhythm disruptions. Natural light exposure, especially in the morning, helps regulate the production of melatonin and reinforces the body’s internal clock. Spending most of the day indoors or in environments with limited natural light can lead to a lack of synchronization between the circadian rhythm and the external environment.

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