Did you know that your body is more than 70% water? The discs are as much as 90%! Water is so vital for every function in the body that it even has a rationing system for when we don't drink enough. The 1st system to dry up is the muscles and joints (musculoskeletal system). This means increased aches and pain. The next to suffer is the gut and digestive tract. Finally, the nervous system loses out resulting in headaches, dizziness, even coma and death. Think of the morning after a night of heavy drinking. A hangover is really dehydration in a massive way.
How much should you drink? Most adults need half the body's weight in ounces. So, if you weigh 160lbs- drink half that or 80 ounces of water- each day. Yes, you will be in the restroom a lot more but only at first. Within 2 or 3 days most people get used to the increase and the peeing slows down.
Unfortunately, coffee, tea, and soda don't count towards your water. They actually make it worse. There are some "green" drinks that can help in a big way. That gets us into a discussion of pH and that is another post.