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Nutrients · Active Vegan Talker Joined: 15 Jan 2007 Posts: 26

Water is essential for all life on Earth, including mammals and mankind. Humans can survive for several weeks without food, but for only a few days without water. A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, sweating and urination. Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, although it provides only a small fraction for humans. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism; for example sodium, potassium and chloride are common chemicals found in very small amounts in most waters, and these elements play a role (not necessarily major) in body metabolism. Other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels.

About 70% of the fat free mass of the human body is made of water. To function properly, the body requires between one and seven litres of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people. For those who do not have kidney problems, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) it is dangerous to drink too little. People can drink far more water than necessary while exercising, however, putting them at risk of water intoxication, which can be fatal. The "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source. There are other myths such as the effect of water on weight loss and constipation that have been dispelled.

The latest dietary reference intake report by the United States National Research Council recommended (including food sources): 2.7 litres of water total for women and 3.7 litres for men. Water is lost from the body in urine and feces, through sweating, and by exhalation of water vapor in the breath.

Humans require water that does not contain too many impurities. Common impurities include metal salts and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for taste enhancement and to provide needed electrolytes. The single largest freshwater resource suitable for drinking is the Lake Baikal in Siberia, which has a very low salt and calcium content and is very clean.

From Wikipedia, the free encyclopedia

Quantity of Water in Fruits, Vegetables and other natural foods per 100g of edible portion.