Water plays an important role in the life of the organism. Most of the substances, which are necessary for normal functioning of organs and tissues, are soluble in water. It is an environment in which almost all the biochemical and biophysical reactions associated with metabolism and necessary for life run. Water acts as a transport system (transport of nutrients, enzymes, metabolic products, gases, antibodies, etc.). With the help of water metabolic products (slag) are excreted, a state of homeostasis (acid-base, osmotic, hemodynamic, thermal equilibrium) is supported; cool down of the body occurs by means of evaporation of water through the skin and lungs. Water is essential for the formation of secretions and excretions, providing a certain tissue turgor; it contributes to the dilution of feces.
The organism needs for water corresponds to the amount of the lost fluid. Under normal conditions, water loss in an adult per day is, on average, 2300-2800 ml (urine – about 1500 ml, by sweating and evaporation – 400-700 ml when breathing – 300-400 ml, with feces – 70-200 ml). In connection with this, an adult person requirement in water is on average 35-45 ml per 1 kg of body weight. During heavy physical work and high ambient temperature (in warm climates, in hot shops, and so on) water loss of the body, and hence the demand for it, increases.
Usually dehydration is indicates by sensation of thirst, which occurs when the corresponding excitation of the nerve centers associated with an increase in the osmotic pressure of blood. Water absorption occurs primarily in the intestines. As it enters the blood in about 10-20 minutes, in connection with which thirst quenching does not always occur immediately after drinking some liquid. Therefore, under conditions of high ambient temperature when sweating a one-time use of large amounts of fluid is not justified as it only increases sweating. It would be more physiological to drink a few sips of water with short intervals (5-10 min). More effective way to quench your thirst is drinking water with the addition of organic acids (citric, etc.), or slightly salted (0.5%). It is recommended to use in hot shops and in hot climates.
Water retention in the body is, in addition to sodium, due to excess food, foods rich in carbohydrates and proteins. Potassium and calcium stimulate the excretion of fluids from the body. High content of potassium and calcium explained diuretic effect lacto-vegetarian diet.
The use of excessive quantities of liquid affects the cardiovascular system and the kidney, promotes the disintegration of the protein leaching from the body of mineral salts, water-soluble vitamins, nitrogenous, sulfate, and other compounds.
Restriction of fluid intake contributes to the breakdown of proteins and fats, followed by the accumulation in the body of the decay products, leads to a reduction in the mass of circulating blood and its condensation. The complete absence of fluid a person suffers much heavier than food deprivation (in the absence of food and the use of water, he can live 30-40 days, and the deprivation of water he would be dead within 5-6 days).