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It would be too long a story to tell why and how we develop our beliefs and convictions. Neither one of us has enough time or educational background to be able to analyze and form an informed opinion about each aspect our lives. Consequently, we are relying on others, who are considered to be the experts in the corresponded fields. The healthcare is not an exception.
There is an opinion, that drinking large amount of water prevents dehydration. It seems to be logical to think so using our “common sense”.
It had been accepted as an axiom, and practically no one until recently was challenging this belief. Surprisingly, “the water axiom” has not been supported by the scientific evidence.
It is important to remember in regards to the health issues, that many popular in the past beliefs have later been proven wrong and fell out of fashion, being successfully replaced by new.
The water is a necessary daily product. Although it doesn’t provide the calories or vitamins, it’s needed for removing toxic products of metabolism through the urine. The danger of not drinking enough is more related to the intoxication with the products of the body’s metabolism, than to the actual loss of water. Is everyone regardless the body-size, eating habit, physical activity, and the climate zone requiring a gallon of drinking water daily in order to feel good?
Not enough water can cause you feeling intoxicated, and fatigued. In a hot day and under vigorous physical activity, the water restriction can easily produce that effect. What about too much water? Too much water over of short period of time can cause water intoxication. It happens when the rate of water consumption exceeds the kidneys’ capacity to process it into the urine. The excess of water in the plasma enters the cells, leading to their swelling. When the brain cells swell, it can lead to the life threatening situation. What if we drink more than the body requires on the daily bases? The body would use adaptational mechanisms to adjust to such habit. As a general rule for all adaptational mechanisms, the body’s capacity of handling excessive amount of water is also limited.
The social media is saturated with the testimonials from people drinking daily a gallon of water for a month or longer. All agree, that it takes the will power making it to happen, particular at the beginning of their trials. It seems the body tries to prevent us from doing it. Majority of people start doing so “to clean the body from toxins”. Some, to prevent dehydration, particulary during the exercise. Surprisingly, and against “the common sense”, drinking water doesn’t prevent dehydration. It doesn’t do so, according to the experts**. In 2011 the European Union court banned the bottled water manufacturers proclaiming, that drinking water prevents dehydration. They were prohibited from printing that on the labels. The court decision withstood the legal challenge, but it was publicly criticized as illogical*. The scientists behind “an illogical” conclusion have apparently used a different logic.
The body physiology is quite a complex thing, where not everything is following a formal logic applicable to some other things.
Understanding of why drinking water cannot prevent dehydration requires certain amount of knowledge. For example, some basic knowledge about our own urine. Talking to my patients I discovered, that some didn’t know how the urine tastes. It tastes salty, which indicates, that besides the water, it contains something else. That is the salt we eat every day, namely Sodium Chlorite. Why does it contain the salt, while the only things we needed it to carry out with the water of our body are the metabolic waste and environmental toxins? So called osmolarity process, used by kidneys in urine production is responsible for that. The urine is formed from the liquid portion of the blood - plasma, while the blood passes through the kidneys. In order to preserve water as one of the most valuable body commodities, the kidneys concentrate soluble in water waste in to the smallest possible volume of water. This process cannot be achieved through a simple filtration, but through the osmotic extraction, and so called active transport, where Sodium Chlorite plays a crucial role. Although, Sodium Chlorite is also a very valuable body commodity, the kidneys wouldn’t be able to expel any amount of water out without loosing some of the salt. Different animals possess different ability to concentrate and to dilute their urine. If the avarege normal human plasma osmolarity is 280 mEq/L, the urine can be diluted down to 50 mEq/L, or concentrated up to 1400 mE/L. Osmolarity is measured by the amount of other than water molecules particles in the water. Sodium Chloride is the most predominant molecule responsible for urine osmolarity.
The next question I usually ask to my “water-men and women”: Where is that 1/2 gallon of water retained in your body after drinking it days after days? If it is not in the body, it must be taken out the body with the urine. But, in order to make that amount of urine day after day, we need a lot of salt. The more water we drink, the more we need to pee out, the more salt we need to form the urine. Where is that daily needed amount of salt coming from? From our food, and when we do consume enough salt with our diet, we start losing salt from the body. First, it’s coming from the plasma of your blood, and later, in order to compensate, from the cytoplasm of the cells, to maintain the equilibrium in osmolarity between the cells and the surrounding plasma. More interesting, because the water molecules are small and easily filtered through the kidneys’ membrane, in order to stay in the circulation, the water molecules have to be attached to the other molecules: amino acids, proteins, and salts’ ions, forming micelles. We remember from school, that water molecule is a dipole, looking like a triangle, with a negative charge on the oxygen side, and positive charges at the hydrogens sides. Micelles are bigger particles, and normally cannot be filtered through the kidney so easily. That way the water remains in the circulation. It cannot be retained in its fee form, but only if it’s attached to the other charged molecules, mostly ions. What happens, when the body loses some of the sodium ions, needed to form the urine? There will be less ions available to form the micelles and hold the water in the circulation. Less water in circulation means dehydration. This sounds very paradoxical: it comes out, that drinking excessive amount of unsalted water for long period of time can cause dehydration…, and it actually does. In my practice, I encounter the patients who were, in fact dehydrated due to excessive water consumption. They would experience all the classical symptoms of dehydration, such as fatigue, orthostatic hypotension (drop of the blood pressure when attempting standing-up abruptly from sitting or lying position), headaches, dizziness, tachycardia (fast heart rate), dry mouth, constant desire to drink more water, anxiety, and “a dropping sensation” in epigastrium, similar to what we experience with intense fear or during the turbulence in an airplane, and what by some of my patients is interpreted as panic attacks.
When we are trying to understand what is natural and not for us as humans, we should not ignore looking at ourselves as a product of evolution, and having common roots with the rest of the animal world. We, as species, like the rest of the animals, were not always living surrounded by plenty of resources such as the food and water.Those of humans, living in Africa are still experience droughts, and frequent famine.The human body is better equipped to survive with minimum food and water, than with their excess. We can survive for a month without food. The water is needed to eliminate daily metabolic waste from the body. Two days without water can put you in a very dangerous and irreversible health condition. But, when the situation arrives, the kidneys are equipped with a very efficient mechanism making the urine more concentrated to preserve water loss. On the other hand, because it is unnatural for the humans and other animals drinking in excess, we didn’t develop a mechanism to dispense water out of the body in its pure form without using and loosing salts. Thus, there is a threshold in how much of water the body can handle without starting loosing more electrolytes than come with the food. How would one be able to calculate that threshold? It’s a very good question. First of all, in accordance with the body size, age, gender, activity level, the climate where we live, and so on, it must be a different threshold for each of us. Even, there was a formula allowing to calculate it for each of us individually, it would be a quite complicated one. Let us to make sure, that we don’t skip meals, which many of us do trying to loose weight. You can change the amount, and what you eat by still keeping it three meals a days, but having one meal a day is not an option.
Hope, it helps you to understand, that it is not the water, but food prevents dehydration. Some people, particularly with chronic constipation do benefit from excessive amount of water, because it helps to remove the toxins. As for the rest of us, I don’t see any other health benefits of drinking excessive amount of water. Unless, …your goals are not related to your health, but supporting the bottled water industry.
Vitaliy Shaulov, MD