There is no other contribution we make to our bodies on a daily basis that is more important to our health than drinking plenty of water. At nearly 70 percent, our bodies are mostly made up of water, and our blood is about 90 percent water. We can go a few weeks without food, but we can only survive a few days without water. The average person loses two to three liters of water every day, through sweat, urine, respiration, and cellular function. And yet, so many people go through their days dehydrated.