Water is a combination of hydrogen and oxygen. It is the basis for the fluids of the body.
Diet - water; H2O
Water makes up more than two-thirds of the weight of the human body. Without water, humans would die in a few days. All the cells and organs need water to function.
Water serves as a lubricant. It makes up saliva and the fluids surrounding the joints. Water regulates the body temperature through perspiration. It also helps prevent and relieve constipation by moving food through the intestines.
You get some of the water in your body through the foods you eat. Some of the water is made during the process of metabolism. But drinking water is your main, and best source, of water.
You also get water through liquid foods and beverages, such as soup, milk, and juices. Alcoholic beverages and beverages containing caffeine (such as coffee, tea, and colas) are not the best choices because they have a diuretic effect -- they cause the body to release water.
If you do not drink enough water each day, the body fluids will be out of balance, causing dehydration. When dehydration is severe, it can be life-threatening.
Although there is no research to identify the exact amount of water you should drink, experts usually recommend drinking six to eight 8-ounce glasses of water daily.
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Wolf R, Wolf D, Rudikoff D, Parish LC. Nutrition and water: drinking eight glasses of water a day ensures proper skin hydration - myth or reality? Clin Dermatol. 2010;28:380-383.