Water, which scientists estimate comprises approximately 60 to 75 percent of the human body, is important for three primary reasons: it acts as a solvent, it acts as a lubricant, and because it changes temperature slowly, it is vital in regulating the body’s temperature. The first reason because it is a solvent-means that many substances can dissolve in it, which allows nutrients and other vital components to be transported throughout the body. This is because the body’s main transportation systems, blood, are largely composed of water.
Therefore, substances like glucose (which comes from food) that are needed for energy in the body can be dissolved in the blood and then delivered to the heart and cells. Another important function is the elimination of waste. Materials that the body does not need, called waste products, are dissolved in the water component of urine and then flushed out of the body through the urinary system.
In addition to acting as a solvent, water is a lubricant, which means it prevents friction between the various surfaces inside the body, such as bones and blood vessels. One example of water acting as a lubricant is in the diges tive system. One of the fluids present in this system is the fluid mucus, which, like blood, is primarily made up of water. Mucus enables food to move through the intestines and be digested, providing the body with fuel.
The third function of water in the body is that of a temperature regulator. The temperature of water does not change quickly-it has to absorb a lot of heat or lose a lot of heat before the temperature increases or drops. This property enables the body to stay at a fairly constant temperature. In addition, water does an important cooling job for the body in the form of perspiration. When the body is absorbing an excess amount of heat, sweat forms on the skin, which allows the heat to escape the body without damaging any cells.