Water is essential for life and conditions practically all biological functions of the human being. Our body is made up of 60% water, but more specifically this percentage increases to 70% in the brain, 80% in the blood and 90% in the lungs. Without this fluid, blood pumping, thinking and breathing would be impossible, so life itself could not be achieved in any way.
On average, human beings lose about 2.3 liters of water per day, whose value is divided into the following values: urine is responsible for discarding 1-1.5 liters, sweat 0.3 to 0.9 ( depending on physical activity), respiration about 0.4 liters and feces 0.1-0.2 liters. Even exhaled air is essential to maintain the body’s water balance, since we lose about 350 milliliters of this fluid with expiration, in the form of vapor.
As you see, we are an open system that loses water, heat and organic matter at all times. For this series of reasons, it is necessary to maintain a constant intake of nutrients and water, but do you know how much water you should drink per day? Here we give you an answer, based on the science and research proposed recently.
Osmolarity is a measure used to express the total concentration of substances in solutions, with the parameter osmoles/liter Osmolality, on the other hand, uses osmoles/kilogram of liquid values, but in dilute solutions (such as fluid media within the human body), both terms can be conveniently used interchangeably.
People with a plasma osmolarity between 285-295 mOsm/kg are considered hydrated, regardless of the level of urine produced and water intake The brain directly modulates both vital functions based on the concentration of body fluids, so knowing the osmolarity of blood plasma is “sufficient” to be able to estimate the state of a patient at a given moment.
This formula It encompasses the 3 solutes most present in blood plasma, which are sodium, glucose and urea The normal range for blood sodium levels is 135-145 milliequivalents per liter, while glucose is considered correct when the value is less than 5.6 mmol/L: beyond this, prediabetes/diabetes is considered. On the other hand, urea, the final product of protein metabolism, occurs in plasma ranges of 12-54 mg/dl.
All of these values depend on the percentage of solutes present in the plasma, but also on the water available to the body, since we remember that 80% of blood is water. The more water we have available at the body level, the more diluted a sample can appear, within the limits of normality.
How much water should you drink daily?
Based on this extensive but necessary introduction, it must be taken into account that What is really important is the osmotic balance in our body, beyond arbitrary values in liters of water, when talking about intake A person can lose up to 1% of their body weight in sweat when performing demanding exercise, so naturally, their water consumption should be much higher than that of someone who hasn’t left the couch all day.
In any case, there are a series of average values that can be established in the general population. The European Food Safety Authority made a list in 2010, with the intake of milliliters of water per day, in different age groups The average values are the following:
As you can see, The values vary greatly depending on the age group analyzed and, also, based on the government sources consulted We can conclude that most men should ingest 2.5 to 3 liters (depending on their demand and physical activity), while women require a little less, 2 to 2.5 liters. This distinction is purely arbitrary, simply based on the fact that men tend to have a slightly higher muscle mass.
Studies like Water Intake, Water Balance, and the Elusive Daily Water Requirement (Nutrients Magazine) have tried to accurately quantify the importance of these figures at a neuroendocrine level. The brain constantly acts to maintain the internal homeostasis of the body, so it is expected that the plasma concentration of hormones and neurotransmitters will vary according to the physiological needs at all times
With this idea in mind, circulating vasopressin levels have been quantified in patients at different times of the day. This hormone is the main regulator of body fluids, it is produced in the hypothalamus and is stored and released through the neurohypophysis. It causes vasoconstriction, water reabsorption at the kidney level and acts as an antipyretic/pain reliever, among other things.
The intensity of the neuroendocrine response (using circulating vasopressin levels as a parameter) allowed us to contrast that the typical brain mechanisms of dehydration begin to activate, on average, when the person consumes less than 1.8 liters of water per day.
Besides, Up to 71% of adults consume less than this daily value in some countries, showing mild signs of dehydration throughout the day These values show that the majority of the population does not respect the minimum Daily Total Water Intake (TWI L/24H) so that neuroendocrine defense methods do not appear in the event of dehydration.
How do you know if you drink too little water?
The normal range of water in the body during a day is less than 2% of the patient’s body weight. Thus, Hypohydration is defined clinically as a state in which the person loses more than 2% of weight per day due to this condition Dehydration (next step of the clinical event) is considered when body water loss is above 3%.
Dehydration (mild to severe) manifests itself with symptoms such as dry mouth, fatigue, weakness, irritability, dizziness, nausea, headaches, constipation, dry skin, and many other events. It can be caused by a lack of water intake, but some infectious pathologies (such as bacterial infections that cause vomiting and copious diarrhea), hormonal imbalances (effects of chronic diabetes) and even organic problems (in the liver, kidneys, etc.) can lead to dehydration in the patient.
Sometimes avoiding dehydration is a matter of responsibility, while in other cases it does not depend at all on the patient’s disposition Diabetics who feel signs of dehydration or patients with acute intestinal infections, for example, should immediately go to the emergency doctor. Sometimes, intravenous fluid therapy is the only possible approach to avoid complications.
Summary
As you have seen, to the question of “how much water should you drink a day?” Multiple things can be answered, always taking into account the individual condition. Firstly, intake depends on the person’s age, sex and physiological state, for example, pregnant women should drink almost half a liter more daily than non-pregnant women.
In general, it is estimated that about 2 liters of daily intake for women and 2.5 for men are sufficient, but the figure can increase significantly more if we are talking about athletes or people with a very high body mass index. In any case, below 1.8 liters of intake, neuroendocrine responses associated with dehydration begin to appear, so this is a clear reference “cut-off point” for every functional adult.
