Are eight glasses of water necessary?

DEAR DR. GOTT: Please explain where the idea of drinking “eight glasses of water a day” comes from. I have found no logical explanation.

DEAR READER: Water makes up almost 60 percent of a person’s body weight and is vital for our well-being. It flushes toxins from the system, carries nutrients to all cells, and keeps us properly hydrated. So how much is too much?

There is no scientific basis for the amount of fluids a person should ingest. Eight glasses of water daily is simply an easy rule of thumb. The recommendation for all fluid intake is 9 cups for women and 13 cups for men. This includes coffee, tea, milk, breakfast juices, soup broth and so forth. Keep in mind that we lose almost four cups of fluids daily because of sweating, urination, bowel movements and breathing. Then there’s humidity, illness, the occasional fever and exercise to consider. People who live in humid areas, have specific disorders, or are physically active may require additional fluids because they sweat more than someone sitting behind a desk.

Unless a medical condition or daily routine dictates diligent attention to fluid consumption, it certainly isn’t necessary to keep a checklist. Don’t allow yourself to become dehydrated; drink when you are thirsty. If you plan to hike, jog, play tennis, or perform physical activity, take along a water bottle and hydrate periodically.
A good rule of thumb is to hydrate at appropriate times throughout the day and include a glass of water with meals. If your diet is a healthful one, you should have your fluid intake covered adequately.