Eight glasses of water
Everyone knows that a person can only live without water for a few days, but there is practically no scientific evidence of the effect of drinking a large amount of water on the body. It is believed that water is useful in all respects, from cleansing the body of toxins and maintaining the normal condition of organs to weight loss and improving complexion. According to near-medical publications around the world, the phrase has been roaming for decades that scientists recommend drinking 8 glasses of water every day.
Obviously, the original source of these glasses are half a century old recommendations of the National Academy of Sciences of the USA (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). Perhaps, in their recommendations to drink 1 ml of water for each kilocalory of food consumed (the diet of a modern person is on average 2000-2500 kcal), the authors relied on some earlier studies. Maybe this proportion – a milliliter per kilocalory – is even scientifically sound, and not taken from the ceiling. But, as often happens, the following phrase of the recommendations of the best nutritionists was forgotten by the retellers – and then it says that most of the required amount of water is contained in the food consumed.
The question of the optimal amount of water consumed has been studied by many researchers, but it was possible to bring disparate data into a single system only with the help of meta-analysis. Dan Negoianu and Stanley Goldfarb from the University of Pennsylvania analyzed the results of published clinical studies on this issue. They found strong evidence that individuals in hot, dry climates, as well as athletes, need a lot of water. (It would be strange if it turned out to be the opposite, but now this obvious fact can be considered scientifically justified.)
In addition, the use of additional fluid helps to improve the condition in certain diseases. However, no such data has been obtained for healthy people living in normal conditions and leading a normal lifestyle.
Analysis of the results of studies on the effect of large amounts of water on kidney function and the elimination of toxins showed that heavy drinking does have a certain effect on the excretion of various compounds by the kidneys, including sodium and urea. However, none of the studies found any positive clinical effect of this phenomenon.
It has been established that the retention of water in the body depends on the speed of drinking. If a person drinks in quick sips, the water is excreted quickly, and if it flows slowly, it lingers in the body for a while. However, there is no evidence of the benefits of drinking large amounts of water, regardless of whether to drink it in one gulp or in small sips.
The authors also examined the widespread opinion that an additional amount of water suppresses appetite, promotes weight loss and even helps in the fight against obesity. However, this statement is groundless (in any case, unsubstantiated), because at the moment there has not been a single carefully planned clinical trial of the effect of drinking water on a person's weight.
Headaches are also often associated with dehydration, however, confirmation of this was obtained during one small trial in which drinking a large amount of water actually reduced the number of headache attacks in patients compared to the control group, but the data obtained were not statistically reliable.
Water is also presented as an elixir to improve skin color. However, despite the fact that dehydration reduces the elasticity of the skin, there is no evidence of a positive effect on the skin of a large amount of water.
Thus, the results of a review of the scientific literature indicate that there is no convincing evidence of the benefits of drinking large amounts of water. However, the authors emphasize that there is also no evidence of the lack of benefit, so today it is illegal to make any recommendations about the amount of water consumed.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
04.04.2008