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Among the most recent debates on water needs is the one opened in the British Medical Journal by a general practitioner, Margaret McCartney, who criticises the standard recommendation adopted by the British health service to drink 8 glasses of water a day. “It is a myth, there is no scientific evidence of its usefulness, moreover drinking too much can lower sodium levels and expose to possible contaminants in the water”. The issue is discussed, everyone agrees that hydration is essential for the body, but there are many opinions on how and how much. Or use drink water app.


Do we really need that much to drink? “Water introduced with food and drink is an essential nutrient – explains Valeria del Balzo, of the Food Science and Nutrition Research Unit at the Sapienza University of Rome – because it is a source of mineral salts, is involved in functions such as the regulation of cell volume and body temperature, promotes digestive processes, plays an important role in diluting orally ingested substances, makes it possible to transport nutrients and promotes the removal of metabolic waste. The American Society of Nephrology claims that there is no scientific evidence on the benefits of high water consumption but it is important to keep the amount of water in the body constant”. That is to balance the inputs and outputs.


In order to understand how much to drink, it is necessary to think in terms of the balance between the water that is lost and the water that is taken. The exits consist of sweat, water vapour from the mouth, faeces and urine. “Every day an adult loses about 600-1000 ml of water between water vapour that saturates the exhaled air and water lost through the skin by exhalation” quantifies Valeria del Balzo. Much depends on the temperature, both the body and the environment, which is why in summer you need to drink more. “An increase in body temperature of 2°C increases evaporation by 50%, the increase in external temperature from 24°C to 31°C doubles the loss of water through perspiration (water vapour and sweat). The thirst mechanism, regulated by the hypothalamus, together with water reabsorption in the kidneys maintains the water balance. Thirst regulates the amount of water to be ingested but often intervenes only when the loss of water has already been such as to cause the first negative effects”.


“The intake of water can take place at any time of the day, in response to the sense of thirst” recommends Valeria del Balzo. And it is good to remember that there is not only water from the glass or bottle, but “any type of drink and also the water contained in food (especially fruit and vegetables) contribute to the total intake of water – she concludes – It is still a good habit to drink during meals, because digestion requires water”.

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