How much water makes up each of us varies from person to person. For example, the leaner a person is, the higher the proportion of water in his or her body. Males carry a higher percentage of water than females, because male bodies have more muscle. Muscle tissue is about 73 percent water, while body fat is about 25 percent water. Even bones are 22 percent water.
Water plays a number of important roles in the body.
It regulates body temperature, carries nutrients and oxygen to cells, removes waste, cushions joints and protects organs and tissues. Since the brain is 70 percent water, blood is 82 percent water and the lungs are nearly 90 percent water, it is easy to see how even mild dehydration can cause problems. Not only is water a necessary part of every system in the body, but the water we do have is also lost from the body in a variety of ways. Water is expelled from the body by the skin as perspiration, by the lungs as water vapor exhaled, by the kidneys as urine and by the intestine as feces. That's why health professionals agree we need eight to 12 glasses of water a day to maintain healthy, adequate hydration.