Introduction
It is now known to all that the organism is mainly made up of water. This, distributed both inside and outside the cells, is constantly subject to change.
The main ways of elimination of water are: urine, faeces (which include digestive juices), sweat and water vapor for pulmonary ventilation. The only natural way of introduction instead, is constituted by the diet.
Especially in the summer, in case of demanding physical activity and following pathologies that have caused vomiting or diarrhea (but not only), it is essential to drink (and eat *) in proportion to the water losses suffered.
* Not everyone knows that most dietary water comes from food.
Dehydration, or in any case a "chronically" non-optimal "hydration, can increase the risk of various uncomfortable conditions, acute (such as low blood pressure) and chronic (such as renal and biliary lithiasis).
To avoid this, it becomes essential to implement the global water intake, not only by drinking, but also by preferring significantly hydrated foods (vegetables, pulpy fruits, etc.), milk and yogurt, various kinds of drinks, etc.
However, it must be said that, during the day, a person spends on average 1/3 of the time sleeping. During this period, not only is it impossible to eat and drink, but some fluid loss "should" still occur.
In this article we will try to better understand what happens during sleep, if it would be advisable to drink even in this time frame and why.
Drink at night
We drink little at night; it is undeniable.
However, if almost all people do not feel the urge of thirst in the period of sleep - with a few exceptions related to an excess of salt at dinner - and do little pee, there must be a reason.
Is it possible that evolution has neglected such an important aspect for survival?
Why do we drink little at night?
Because the interaction of three specific groups of nerve cells, present in the hypothalamus (deep area of the brain), prevents the dehydration of our body during sleep.
Therefore, when we sleep at night, can we go several hours without drinking?
The answer comes from the "University:" McGill University Health Center "in Montreal.
Scientists recently described the changes our body makes to prevent dehydration during the hours of sleep.
There is an antidiuretic hormone, vasopressin, which controls fluid retention in our body. This is secreted by the cells of the hypothalamus, which in turn are activated by a group of nerve cells called osmosensitive cells, capable of detecting concentrations of water in the blood.
In conditions of dehydration, the electrical activity of these cells is amplified so as to stimulate the production of vasopressin by the hypothalamus. Thus, thanks to the formation of more concentrated urine, vasopressin determines the recovery of body fluids.
C "is therefore a proportional relationship between osmolarity, ie the concentration of solutes in the plasma, and secretion of vasopressin.
In the hypothalamus, in addition to osmosensitive cells, there is also a suprachiasmatic nucleus; it is a group of cells that regulates the daily rhythms of our organism.
By studying the connection between these three groups of cells, two Canadian scientists (Eric Trudel and Charles Borque) found that during sleep the connection between osmosensitive cells and those that secrete vasopressin is strengthened. In this way, even the slightest lack of water is able to cause a huge release of the hormone. Furthermore, the activity of the suprachiasmatic nucleus is also reduced.
Subsequently, the two researchers from McGill University Health Center artificially stimulated the activity of the suprachiasmatic nucleus and observed a consequent weakening of the connection between osmosensitive cells and cells that secrete vasopressin.
It is therefore deducible - and the results confirm it - that the suprachiasmatic nucleus acts as a "brake", inhibiting the secretion of vasopressin by the "hypothalamus.
During the day it is sufficient to drink some liquid to remedy the low concentration of water; on the contrary, when we sleep, the activity of the suprachiasmatic nucleus is reduced, thus allowing a greater release of vasopressin than that recorded during the day. As a result, there is greater fluid retention.
Note: this work was published in "Nature Neuroscience".
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