Proper hydration helps our digestive system run smoothly, keeps our cells young and helps our immune system fight infection. So it would make sense that the more you guzzle, the healthier you’ll be, inside and out, right? Not exactly, says Rolls. “For most of us, fluid balance is not a problem.” In other words, you’re getting enough water already, sans that fancy water bottle glued to your hand. It’s time to get real about water—read on to get the facts, not fiction.
Experts stress that we need to broaden what we think of as water. “Many people think that the only way to hydrate is with plain drinking water, but that’s just not true,” says Keith Ayoob, R.D., associate clinical professor of pediatrics at Albert Einstein College of Medicine in New York.
Currently, the National Institute of Medicine recommends that women get 2.7 liters (about nine cups) of water per day. But the suggested sources go beyond glasses of clear water. All beverages, including water, as well as moisture in foods like fruit, vegetables, lean meat and soups count.
“When you think about it, both coffee and soup—even soda—are mostly water,” says Ayoob. “Any type of fluid goes toward your daily quota.”
But what about the 8 x 8 rule (drink eight glasses of eight ounces of plain water per day, on top of everything else)? There’s no scientific evidence backing that recommendation.
A Dartmouth physiologist named Heinz Valtin conducted a comprehensive search for the origin of this widely repeated statement and published his findings in the American Journal of Physiology in 2002.
Not only did he conclude that there was no evidence to suggest that healthy adults needed to drink large amounts of water, but he also found a possible reason for the long purported myth: a misinterpreted National Resource Council suggestion from 1945.
The original text stated: “A suitable allowance of water for adults is 2.5 liters daily in most circumstances. An ordinary standard for diverse persons is one milliliter for each calorie of food. Most of this quantity is contained in prepared foods.”
He suggested that the last sentence was possibly ignored and the statement as a whole interpreted as you must drink eight glasses (2.5 liters) of water each day.