First of all, say this: if you walk down the street in the heat, working physically in the heat or exercising in the heat, you should drink plenty of water. Probably, even more than two liters of water per day — depends on load and temperature. This article is about something else and for other.
First of all — where are the indispensable information about two litres? Our grandmothers didn't hear, so this came to us from the West in the last 25 years. The majority of researchers "the problems of two liters" agree that the original recommendation is this publication, 1945, which States: "a Suitable amount of water for adults is 2.5 liters of water a day ... Most of this fluid is contained in the food that we consume". As usual, the last sentence is "lost" (or was subtracted from the 2.5 litres) and there was only: "it is necessary to drink two liters". Though bursting.
But, maybe the ancestors were not wrong? Maybe the energy consumption of this amount of water has some bonuses? As they say fitness experts — "flushes out toxins"?
Actually the water there is one undeniable bonus, not disputable — it has no calories. So, if it was replaced with a glass of water a glass of juice and, especially, of soda, would be much thinner, if not healthier.
Many believe that two liters of water is recommended to drink doctors. But doctors, especially value their reputation, such as specialists Mayo Clinic, say, what we are talking about consumption of ANY liquid, not just water. Including what is found in vegetables and fruits, as well as almost any cooked food. And Yes, the soda too (unfortunately). Just like in that publication, 1945.
As for specific scientific and medically proven way of bonuses to HP, it seems not. Take, for example, the risk of mortality from cardiovascular disease. In a study conducted in 1980-ies in the Netherlands (the results from last time published in British Journal of Nutrition in 2010, researchers observed 120 thousand subjects for over 10 years — to find out if it somehow sudden mortality with the amount of water you drink. Links not found.
More modern research suggests. This study have not found a connection between water and chronic kidney disease. The authors of this — did not find any connection of water you drink to the health and beauty of skin. Of course, this all only applies to healthy people, patients already picture can be different, don't listen to us, listen to your doctor.
And even when researchers find a connection, it turns out to be... incomplete. The most famous and convincing evidence of the positive impact of water on health was conducted 20 thousands of members of the community of seventh-day Adventists. It turned out that those men who drank at least 600 ml of water a day and those women that consumed at least a gallon of water per day lived longer than vodoprovodnyi. Nevertheless, no two litres of the question — 600-1000 ml of water a day to drink any adult, at least with tea-coffee making facilities.
Of course, there are other studies, for example, here is. It says that 1.5 liters of water a day — all that is necessary to significantly reduce the risk of bladder cancer. But, again, this is not two liters, not even close.
So can we conclude the following: at least a gallon of water per day to drink, probably worth it, especially in summer and especially if you sweat. But drinking is strictly two and not a bit less? Probably, from this there is no tangible benefit and nothing bad will happen if you drink a 1.9-liter, and even of 1.85 liters. Say more: drink only when thirsty — that's okay too. Provided that you are not starving and don't feel the heat, of course.