As you may be known that our body is approximately 60 percent water, According to H.H. Mitchell, Journal of Biological Chemistry 158, the brain and heart are composed of 73% water, and the lungs are about 83% water. The skin contains 64% water, muscles and kidneys are 79%, and even the bones are watery: 31%.Each day, our body must replace 2.4 liters — or about 2.5 quarts of water — through ingested liquid and foods. Our body uses water in many ways. Water cushions and lubricates joints; nourishes and protects the brain, spinal cord and other tissues; keeps the body’s temperature normal; and helps remove waste through perspiration, bowel movements and urination. Humans are composed mostly of water, which is not surprising when we consider that humans descended from single-cell organisms that originated in the oceans millions of years ago. Water is more important for our body’s survival than food. We can live without water for approximately one week, but we can survive without food for more than a month. Lack of water, or dehydration, reduces the amount of blood in in our body, forcing our heart to pump harder in order to deliver oxygen-bearing cells to our muscles. In the early stages of dehydration, we can become dizzy, irritable and experience headaches. As dehydration progresses, we become clumsy and exhausted. Our eyesight fades. In the last stages of dehydration, we may feel nauseous and begin vomiting. Without water, we will enter a coma and die.