Water is the most ubiquitous substance in the human body. It’s used to help bolster functions and processes in just about every system. Because the body cannot manufacture its own water, it must rely upon intake to replace water lost through the natural expulsion of waste. Exercise is an activity that will deplete water content rapidly, meaning that active individuals are dependent upon a constant supply of water.
A human’s total body weight is about 60 to 70 percent water. This figure can change depending on age, gender, weight and body composition. It also varies in small increments throughout the day. Much of this water is amassed in the organs. The brain alone is 85 percent water. Approximately 90 percent of the blood flowing through your veins is also water.
Water is critical to a number of functions in living organisms. It maintains body temperature; metabolizes body fat; plays a role in digestion; lubricates and cushions organs; offers a moist environment to regions like the throat; transports nutrients to the cells; and flushes toxins out of organs. It is also the final byproduct of cellular respiration, in which the cells metabolize a viable source of energy to power the activities of the body.
If your body does not receive enough water, it will begin to pull water from other areas. When this happens in the blood, the capillaries begin to shrink, which makes blood thicker, more likely to clot and harder to pump through the body. The company TheraGear states that this can lead to hypertension, high cholesterol and heart disease.
A lack of water leads to dehydration, which is a condition that occurs when the body no longer has the proper amount of water to carry out its basic functions. Water leaves the body through your breath, perspiration, urine and bowel movements. It must be replaced by the same amount of water taken in.
According to the Mayo Clinic, doctors recommend 8 to 9 cups of water a day for the average, healthy adult living in a temperate climate. About 20 percent of these fluids come from food intake, so an additional 8 cups from beverages will replace approximately 6.3 cups lost from urine and 4 cups lost elsewhere.