We've heard for years that we need to drink eight, 8-ounce glasses of water a day. Before you start chugging, is it true?
"There is no scientific evidence whatsoever for that rule," says Kenney. "It's certainly not a harmful rule, but there is no scientific rationale behind it."
Instead, it's pretty simple: For the average person, drink enough so you go to the bathroom every two to four hours.
"You should be drinking enough so that you urinate every two to four hours, and that the urine is a light color," says Clark, author of Nancy Clark's Sports Nutrition Guidebook. "If you go from 8 a.m. till 3 p.m., and your urine is very dark, that's a sign that you haven't had enough to drink."
Most of us do a pretty good job of getting adequate amounts of fluids as part of our everyday routines: coffee in the morning, soda or juice with lunch, a glass of water in the afternoon, and water with dinner. Coupled with the water that makes up our food, usually, this is sufficient.
Athletes, of course, need more.
"The exact amount of water needed per day really depends on the individual," says Rick Hall, a registered dietitian in Phoenix. "People who exercise, for example, will lose a lot more water through sweat and breathing, so their needs are higher."
Athletes need to quench their thirst even when they're not thirsty, and avoid relying on the feeling of thirst to tell them when to drink.
"Headaches and cramping are common signs of dehydration," says Hall. "However, these are late signs. Unfortunately, the body hides mild dehydration very well, and it can take hours before you recognize that you are dehydrated."
Exercise, explains Hall, blunts the thirst mechanism.
"So folks who are running or biking may not feel thirsty when they actually need water desperately," Hall tells WebMD. "An important strategy is to prevent dehydration by hydrating frequently."
Too Much of a Good Thing
We know we need to drink fluids to maintain a healthy body, but is there such as a thing as too much?