Since about 70% of fat-free body mass is water, it's not surprising that the body must have water to function. An individual might live for month without food but only a few days without water. Water is needed for proper digestion, cell growth, and maintenance. Water also lubricates the joints, body cells, and helps regulate the body's temperature. Water is inside and outside of all cell walls. The body takes the water it needs from liquids and foods that are taken into the body. Most of the water comes from the liquids that are ingested and they can be found in the form of water, milk, coffee, tea, fruit juices, clear soups and other beverages. Eight glasses of liquid a day supplies enough water for most individuals.
The brain needs to be fully hydrated so that the circuitry works at its best. Water is also important for concentration and mental alertness. Studies have shown that most people are permanently partially dehydrated.("Brain Food",2009). A study by Trevor Brocklebank at Leeds University in the UKL discovered that schoolchildren with the best results in class were those who drank up to eight glasses of water a day (Lucas, 2001).