Camino hacia el descanso profundo

Path to deep rest

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We live in the society of "hyperproductivity". A hyper-stressed society in which a night of rest has become a limited good , a luxury good for many that is difficult to reach.

Although we are all aware of the importance of sleep, it seems that any activity is more important than going to bed at a good time, we prefer to distract ourselves with the latest Netflix or check Instagram . However, when the alarm clock sounds first thing in the morning, you regret not having gone to bed at least a couple of hours earlier.

In today's article, we explore the science of biorhythms and possible tools to implement to improve their function and consequently improve your health.

1. The importance of the circadian cycle

If there is an issue in which there is agreement within the scientific community, it is the importance of respecting the circadian cycle , where sleep is only one part.

If the Guinness Book has not accepted as a challenge "maximum hours without sleep" considering it something extremely dangerous for health, it is for a reason and, it is not lacking in good sense.

What is the circadian cycle?

Every living being has an internal "clock" that regulates behavior and physiological state 24 hours a day through hormonal secretion, nervous system, endocrine and circulatory system, among others. This clock is highly accurate but adapts to the right stimuli to stay in sync with the sequence of the day. This explains that if we take a crab out of the sea and lock it in a box thousands of kilometers away, it will continue to run to one side when the tide rises from its beach of origin and to the other when the tide goes out. Eventually it will stop, because your internal clock will get out of sync.

We resemble the crab more than we imagine, since something very similar occurs in our species.

What we eat, when we do it, at what temperature, with what levels of stress and, above all, the light to which we live exposed, are factors with a clear impact on our circadian cycle.

If your day begins with the sound of the alarm clock... something is not quite right.

2. The sleep cycle. What happens while you sleep

Sleeping is much more than closing your eyes, it is a biological necessity. Almost no physiological process escapes the effect of sleep or its absence.

While you sleep, the body's physiological recovery occurs. The body repairs itself, detoxifies, muscles regenerate and the brain processes all the information received during the day to acquire new knowledge.

The dream

Sleep is a dynamic process, made up of several cycles that are repeated every night. Each cycle is made up of an active phase ( REM : Rapid Eye Movement ) and a quiet phase ( NREM : N or Rapid Eye Movement ).

It is made up of four subperiods : NREM1, NREM2, NREM3 and NREM4. As these phases progress, we enter an increasingly deep sleep where the muscles relax, the heart rate drops and brain activity slows down more and more. It is in the NREM3 and NREM4 periods that the body repairs itself and energy levels are restored.

It is characterized by high brain activity, where memories are fixed and new knowledge is acquired. It is at this stage that the dreams that we remember as stories occur and, unlike the previous ones, here the heart rate, blood pressure and eye movement increase, but the muscles paralyze, that is why we cannot run or scream when we have a nightmare

During the early hours of the night, NREM sleep periods are longer than REM periods, and as morning approaches, the periods reverse, with the former being the shortest.

The complete sleep cycle lasts, in general terms, between 90 and 110 minutes, depending on the person. During this period these five phases occur and are repeated throughout the night. During the night we experience between 4 and 5 sleep cycles. Having a restful sleep will depend on whether or not we have completed each of the phases.

3. Melatonin. sleep hormone

Melatonin is the main hormone involved in the regulation of sleep and wakefulness. It is produced mainly in the pineal gland and is involved in a wide variety of cellular, neuroendocrine, and neurophysiological processes, such as controlling the daily sleep cycle.

Melatonin is synthesized from the essential amino acid tryptophan. Its amount varies throughout life; its levels increase throughout childhood, suffer a sharp decrease at puberty and, from the age of 40-45, they will gradually decrease (1).

Melatonin is directly responsible for a series of crucial functions for our body:

  • Regulates our biological clock (2), makes us sleepy at night. As the day darkens, melatonin begins to be released, peaking between 2 and 4 in the morning. From then on, it gradually decreases, being minimal during the day. The light causes the retina of the eye to send signals to the pineal gland to inhibit its production.
  • It acts as an antioxidant.
  • It has an inflammatory action fighting free radicals (3).
  • It helps improve the immune system by counteracting the immunosuppressive effects of cortisol ( it is the hormone involved in stress processes ) and stimulating the activity of lymphocytes (1).

Although the consumption of melatonin has multiple benefits, it is important to control the daily dose supplied so as not to unbalance the internal processes. The ideal is to always comment with a low dose, which does not exceed 0.5 milligrams daily. Many of the best sleeping pills contain melatonin.

In contrast, lack of sleep and lack of regulation of biorhythms sooner or later end up taking their toll, significantly increasing the risk of suffering from, among others, diabetes and obesity (4), cardiovascular diseases (5), respiratory sleep disorders such as apnea (6), worsens the prognosis in neurodegenerative diseases (7) and insomnia (8).

4. Negative consequences of lack of sleep

As we well know, improving your body and your health implies attending to various aspects of your lifestyle: what you eat , how much you move , emotional well-being and, of course, how much and how you rest .

Do you know how lack of sleep affects you?

  • It interferes with glucose metabolism , making you more resistant to insulin.
  • It makes you more impulsive , our animal brain prevails and we lose self-control, which undoubtedly affects what and how much you are going to eat.
  • Increases appetite , reduces leptin ( hormone that tells you when the body is full ) and increases ghrelin ( hormone that tells you when the body is hungry ).
  • It reduces anabolic hormones (testosterone, IGF-1 and growth hormone) and, on the other hand, favors cortisol elevation, which will limit the hormonal environment for you to build muscle .
  • It increases our susceptibility to suffering from any disease since sleep is closely related to immune function , inflammation and metabolism .
  • Increases the risk of accidents . Poor sleep makes us make mistakes in any activity. 20% of accidents are due to little sleep . After 18 hours awake, your ability to react and attention decrease significantly, it would be similar to drunk driving.


1- Poza JJ, et al., Melatonin in sleep disorders. Neurology. 2018.
2- Duvocovich ML. Melatonin receptors: role on sleep and circadian rhythm regulation. Sleep Med. (2007).
3- Reiter, RJ, Tan, DX, Cabrera, J., et al. The oxidant/antioxidant network: role of melatonin. Biological Signals and Receptors. (1999).
4- Francesco P. Cappuccio. Meta-Analysis of Short Sleep Duration and Obesity in Children and Adults. (2018).
5- Tobaldini, E. et al. Sleep, sleep deprivation, autonomic nervous system and cardiovascular diseases. Neurosci. Biobehav. Rev. 74, 321–329 (2017).
6- Heinzer, R. et al. Prevalence of sleep-disordered breathing in the general population: the HypnoLaus study. Lancet Breath. Med. (2015).
7- McCurry SM, Ancoli-Israel S. Sleep dysfunction in Alzheimer's disease and other dementias. Curr Treat Options Neurol, 5 (2003).

8- Vgontzas, AN, Fernandez-Mendoza, J., Liao, D. & Bixler, EO Insomnia with objective short sleep duration: the most biologically severe phenotype of the disorder. Sleep Med. Rev. 17, 241–254 (2013). 9- Ruhl CE, et al. Association of coffee consumption with gallbladder disease. American journal of epidemiology. 2000



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