Two liters a day

Angry critic: Why did I drink the eighth glass

Alexey Vodovozov, XX2 century

One of the most frequent questions that I am asked at lectures as a toxicologist is whether it is true that for adequate detoxification of the body you need to drink at least 2 liters of water a day. And it seems to have been chewed up a hundred times that this is a myth, nevertheless, every time some new arguments come to light, even references to research. For the hundredth time, we will try to understand this burning issue once and for all.

So. Most often they write something like this about water:

And among these 20 reasons, absolutely amazing ones are called: "Water energizes", "Water is a billion times healthier than sweet soda", "Water prevents some types of cancer", "Drinking a glass of water improves mood", well, my favorite is "Water is not toxic". Let's start with the last point.

The famous phrase of Philip Aureolus Theophrastus Bombast von Hohenheim aka Paracelsus is most often distorted and simplified to "Everything is poison, everything is medicine; both are determined by the dose." We find the German original:

Alle Dinge sind Gift, und nichts ist ohne Gift; allein die Dosis macht, daß ein Ding kein Gift sei (Everything is poison, and nothing is devoid of venom; a single dose makes poison invisible – VM).

And suddenly it turns out that there is not a word about medicines. But there are other important words about the fact that by and large everything in the world is poisonous, if you choose the right dose.

And then it turns out that salt is really a white poison if you shove it into a rat at the rate of 3 g per kg of body weight (strictly speaking, it will be LD50, that is, only half of thoroughly salted animals will die). A terrible thing is also found: sodium glutamate for a similar effect will require 5 times more — 15.8 g per kg of body weight. And finally, the most terrible thing: the same rats can be killed by drinking water at the rate of only 90 ml per kg of body weight.

In humans, such poisoning is described, first of all, in long—distance runners. Actually, it was with individual cases of coma and fatal outcomes in stayers that a close study of water intoxication began.

So, if you get carried away with clean water, it can end badly. But this is exactly what the adherents of the famous eight (and sometimes 10, and 12) mandatory glasses a day stand for:

No, dear citizens, there will be no happiness, there will be hyponatremia, that is, a drop in the concentration of sodium ions in the blood. This indicator is very important, it is in the loss of electrolytes that the main danger of dehydration lies, for example, with cholera or a hangover. It is precisely because of the lack and imbalance of electrolytes that problems with the heart and other organs begin — our cells work on electricity, and the occurrence of impulses is provided by the difference in the concentration of various ions on different sides of the cell membrane. No gradient — no electricity — no action — no life. Everything is quite simple.

Newborns often become victims of hyponatremia when overly caring parents, who have read the posts of other overly advanced parents, begin to give the child plenty of water without any reason. Another source of excess fluid is extremely popular pools for early development, in which children are launched almost from 1-2 months. Ingestion of water occurs involuntarily, and an overdose, more precisely, a critical drop in the level of sodium in the blood, can occur very quickly: convulsions, brain damage, coma, exitus letalis.

And the chronic abuse of water in an adult does not go unnoticed. Swelling, increased load on the heart, etc., etc. So there is no need to push the eighth glass into yourself by force, it is possible that the fifth was already superfluous.

By the way, where did eight glasses come from? No, not from the American dietary guidelines of the 1940s (Food and Nutrition Board, National Academy of Sciences. Recommended Dietary Allowances, revised 1945. National Research Council, Reprint and Circular Series, No. 122, 1945 (Aug), p. 3-18.), as it is commonly believed.

More precisely, yes, and from there, too, but if we dig deeper, we will fail until about the end of the XVIII century and we will run straight into Christoph Wilhelm Gufeland, the life physician of the Prussian King Friedrich Wilhelm III and his most famous book "Macrobiotics, or the Art of Prolonging Human Life" (hello to modern biohackers, Gufeland did the same when it was not yet mainstream). Since 1796, this work has withstood a lot of reprints, many of them have been digitized, for example, anyone can get acquainted with the 1860 version by following the link, and on Lib.Ru a fragment of the translation of the first edition, made by Vasily Zhukovsky, is laid out. The fact that he was a member of many foreign academies of sciences, including the Russian One, did not prevent Gufeland from being a vitalist, interested in Chinese alchemy, the Illuminati and a new trend in medicine invented by his friend, also a doctor and vitalist Samuel Hahnemann — the first works on homeopathy were published in a magazine published by Gufeland.

And what does eight glasses have to do with it? Patience. It's almost done. The book contains many wonderful cases, some of which are at least doubtful. For example, the story of Pert Tsarten, a Hungarian from the village of Kefresh four miles from Temeshvar, who allegedly died in 1724 at the age of 185. Another story concerned his colleague, the chief military surgeon of the Prussian army, who at the age of 80 was alert and preserved. Gufeland considered 7-8 glasses of cold water, which he drank daily from the age of 30, to be the secret of the youth of an elderly military doctor. We know the word "correlation" today, and from the standpoint of vitalism, everything looked very logical — water was a well-known carrier of vital force, and homeopathy was based on this.

However, there was a tangible benefit from Gufeland's work. For example, his name is associated with the boom of "trips to the waters", which swept the population of Europe in the XIX—XX centuries, including the explosive popularity of such mineral and water resorts as Karlovy Vary (in 1756, 134 families visited the city, at the end of the XIX century their number grew to 26 thousand). So the idea of regular consumption of water, including mineral water, did not go away, she quietly lived until 1945 and was framed in the very recommendations that only the lazy one did not refer to on the Internet.

The whole phrase sounds like this:

A suitable allowance of water for adults is 2.5 liters daily in most instances. An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods.

That is, "In most cases, the appropriate amount of water for an adult is 2.5 liters per day. The standard for different people can be considered 1 milliliter for each kilocalory of food." It is from here that those 8 glasses grow: Americans do not particularly favor the SI system, so they have an excellent "8 × 8" formula, 8 glasses of 8 fluid ounces (about 240 ml) each.

However, the devil, as usual, lies in the details, and in this case — in the end of the phrase: "Most of this amount is contained in cooked foods." That is, all water is considered in general — both in juices, and in coffee, and in borscht, and in cucumbers.

But maybe the supporters of excessive hydration are right, claiming that 2 liters of water a day saves from cancer? Indeed, in 1999, the results of a study were published on 47909 men, a fifth of whom consumed 2531 ml of fluid per day or more, a fifth — 1290 ml or less. Each additional glass in this range was associated with a 7 percent reduction in the risk of developing bladder cancer. But. Only in men, only one type of cancer, and taking into account all the fluid, not just water. In addition, the results and conclusions were disputed, other versions were proposed that were not taken into account by the researchers, and they were also not reproduced on women.

Okay, but does it help to lose weight at least? Well, they won't lie on the Internet:

Will be. Let's start with the quibbles: not weight, but body weight. This mixing of very different concepts equally infuriates both doctors and physicists. Now to the point. Yes, indeed, research has been conducted. For example, as many as eight women. This article is extremely interesting, for example, it seems that it does not have a DOI (a digital object identifier that is assigned to all scientific electronic publications). In addition, it cannot be found on the journal's website — the lead author has only six publications there, but the mentioned article is not among them. Larger—scale surveys were also conducted - on 20 men. But according to the results of these and more other studies, questions remained open: how much this effect reduces food intake, how long the effect lasts and how much liquid may be needed to affect the final saturation. But on a larger number of subjects, 24 (!) women, it was shown that water washed down with chicken soup works worse than the same amount of water, but as part of chicken soup, in the sense of preventing overeating. And, most interestingly, these results were reproduced on 5793 Chinese. So it's past again. And so on almost all points.

Conclusion: drink as much water as you want, without focusing on liters and glasses. But the body will not tolerate violence against itself in any form, even the infusion of excess fluid volumes. He will remember, accumulate the effect and take revenge.

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