How much water we need to drink

Monday, 04 בSeptember 2017

The water

It is a long story to tell how we develop out believes and convictions. It would be fair to assume, that neither one of us has enough time or knowledge to analyze each sphere of life, making an opinion about it. Thus, we are relying on the opinions of the others, who considered to experts in each of those spheres. It is true regarding the health related issues as well.

There is an opinion, that drinking large amount of water prevents dehydration. At least, it is seems to be “logical” to think that it does.

No one until recently had been actually challenging that opinion, and it was accepted as an axiom. Surprisingly, this “axiom” has not been supported by the scientific evidence.

It is important to mention, that regarding to the health issues, there had been certain believes, shared by many, and “in fashion” at certain periods of time, which later have been proven to be wrong. From not too long time ago, we can name few: the effectiveness of vitamin C megadoses for treatment of common cold, and cancer; that margarine was “healthier, than natural butter”; the “benefits” of the food artificially depleted of cholesterol; that annual flue vaccinations help to prevent flue.

Today in fashion is the opinion, that drinking plenty of water is preventing us from dehydration. I hear recommendations of drinking minimum a half of a gallon or more daily.

Although it doesn’t provide calories or being used to build something in the body, and it can be recycled inside of the body, the water is a necessary daily product, because it forms the urine, which removes toxic products of metabolism from the body. The danger of not drinking enough is not because less water would stay in the body (dehydration), but because less urine would be formed, and the body be intoxicated.

Should everyone regardless the body-size, eating habit, physical activity, and the climate drink a half of a gallon of water daily and benefit from it? If such rule was applicable to all of us, than there should be “one fits all” health benefit rule applicable to the other things in our lives, namely food, physical exercise, nutritional supplements, effects of the medications, and so on, which is hardly the case.

Not enough water can cause you feeling intoxicated, and fatigued. If you are not a big water drinker, and it’s a hot day, and are you sweating a lot, feeling thirsty, than you may in fact become dehydrated. But, it is not efficient trying to replenish the lost with sweat water with unsalted water. You will understand that from the information provided bellow.

What about too much water? Too much water at once (for example, if you run marathon and keep drinking more than your body required) can cause water intoxication leading to the brain swelling, loss of consciousness, and even death. What if you drink more than you need on the daily bases? The body defense mechanisms to adjust to that are also limited, and although you would not die from brain swelling, it can still cause you some other problems, which develop slowly and over the period of time.

Why at the first place, you regardless of not feeling thirsty would start drinking more water? I guess, by doing that you are trying to prevent dehydration. Does it actually prevent dehydration? Not, according to the recent European Union experts’ based court decision. The court banned the bottle water manufacturers from proclaiming, that drinking water prevents dehydration, prohibiting writing that on the labels. Are you surprised? How come, that the“dehydration” which is lack of water in the body, cannot be corrected by water? It’s seem to be totally illogical to suggest that, at least using “common sense”. The court decision has been publicly criticized by journalists*, but not by the scientists**. Who to trust? I’d probably go with those, who had bioscience as a major.

The body physiology is quite a complex thing, and not everything is always so simple and “logical” at the first glance at least. Let us try to take a second glance at the issues related to the water consumption.

While trying to explain, why drinking excessive amount of water can lead to dehydration, I asked one of my patients, if she new how urine tastes. She didn’t know. In case, not everyone knows, the urine tastes salty, which means, besides water, it contains salts. In order the urine to be formed, it has to contain salts. It’s so called osmolarity process, which the body uses to make urine. The next question I usually ask to my “water-men and women”: Where is 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 with urine. But, in order to make that amount of urine, we need salts. The more water we drink, the more we need to pee out, the more salt we need to form the urine. Where is this daily needed amount of salt coming from? From our food, and when we have not enough food, the salts will be suction out from our 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 filtrated through the kidney membrane, in order to stay in the circulation, they 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 cannot be filtrated through the kidney so easily. That way the water can remain 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 looses 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 up on standing-up abruptly), headaches, tachycardia (fast heart rate), and so on.

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, …you want to support the bottled water industry, helping them with the profit.


Vitaliy Shaulov, MD