Reality: Your body does need a steady supply of water to operate efficiently and perform the many routine housekeeping tasks that keep you healthy and energetic.
That said, there is no scientific evidence to back up the very specific and well-worn advice that you need to drink eight, 8-ounce glasses of water a day (a.k.a. the 8 x 8 rule). In 2002, Heinz Valtin, MD, a retired physiology professor from Dartmouth Medical School and author of two textbooks on kidney function, published the definitive paper on the subject in the American Journal of Physiology. He spent 10 months searching medical literature for scientific evidence of the 8 x 8 rule only to come up empty-handed.
In 2004, the Institute of Medicine (IOM), a division of the National Academy of Sciences, actually set the adequate total-daily-water intake at higher than 64 ounces – 3.7 liters (125 fluid ounces) for men and 2.7 liters (91 fluid ounces) for women. But those numbers refer to total water intake, meaning all beverages and water-containing foods count toward your daily quota. Fruits and veggies, for example, pack the most watery punch, with watermelon and cucumbers topping the list.
But the “it all counts” dynamic cuts both ways. Vasey believes that many people suffer from low-grade, chronic dehydration because of what they are eating as well as what they are drinking. The “I don’t like water” crowd could probably make up their water deficits by eating the right kinds of foods, he asserts, “but most don’t eat enough fruits and vegetables. Instead they eat meat, cereals and breads, which don’t have much water and contain a lot of salt.”
Animal proteins require a great deal more moisture than they contain to break down, assimilate and then flush from the body. And many processed foods, such as chips and crackers, for example, are nearly devoid of moisture, so – like dry sponges – they soak up water as they proceed through the digestive system.
The body requires only 3 to 5 grams of salt a day to stay healthy, but most people gobble up 12 to 15 grams of the stuff daily. To rid itself of the overload, the body requires copious amounts of liquid.
Bottom Line: If you want to stay optimally healthy, hydrated and energetic, it’s a good idea to eat plenty of water-containing foods and drink water throughout the day. And when in doubt, it’s probably not a bad idea to make a point of drinking a little more water, rather than a little less. But that doesn’t mean you need to down eight glasses exactly, or that if you run a little shy of 64 ounces, then something awful is going to happen. Just be aware that the fewer vegetables, fruits and legumes you are eating, and the more dried, processed or chemical-laced foods you include in your diet, the more water you’ll need to consume to compensate.