The Quest for Hydration

Drinking fluids is essential to stay alive. But how much do we really need, and what counts in our quest to stay hydrated?

Medically Reviewed by Michael W. Smith, MD
From the WebMD Archives

It's ironic that the one thing Debbie Scaling Kiley needed was the one thing that was all around her as far as the eye could see, but wasn't for the taking: water. Setting sail from Annapolis, Md., and headed for Ft. Lauderdale, Fla., the boat Kiley and her crew of four were on sank off the coast of North Carolina leaving them with no survival equipment and not a drop of fresh water.

Stranded at sea in a small life raft, the five survivors slowly started to dehydrate, and after several hours, dehydration set in.

"We sank at about 2 p.m.," says Kiley. "By the next morning, we were thirsty, but the cold was more important than the thirst. Later that day, though, the thirst started to drive us crazy. It's a longing like nothing I'd ever felt before; it's nothing like being hungry. It's torturous because there was nothing we could do, but we'd have done anything for water."

By the third day, they were semidelusional, and that night, two of the men on the raft drank seawater to quench their thirst. The next day, in a delusional state, both men jumped overboard.

"By the fifth day, we were so thirsty, we were overwhelmed by it," says Kiley. "We were at the point of believing we were going to die of dehydration. I've been told the human body can last absolutely no longer than seven days, but in many cases, as I believe was the case with us if we had stayed out there longer, a person can only last five or six days."

On the fifth day, Kiley and one other survivor were rescued. They were immediately given ice cubes to suck on and IV fluids to re-hydrate them. Her story, compelling in so many ways, illustrates to the extreme the importance of water and fluids in our lives.

Water: Why We Need It

"Hydration is important because the body is comprised mostly of water, and the proper balance between water and electrolytes in our bodies really determines how most of our systems function, including nerves and muscles," says Larry Kenney, PhD, a professor of physiology and kinesiology at Penn State.

Drinking fluids serves a range of purposes in our bodies, such as removing waste through urine; controlling body temperature, heart rate, and blood pressure; and maintaining a healthy metabolism.

Without it, the body begins to shut down, as seen in Kiley's experience at sea. Symptoms of severe dehydration include altered behavior, such as severe anxiety, confusion, or not being able to stay awake; faintness that is not relieved by lying down; an inability to stand or walk; rapid breathing; a weak, rapid pulse; and loss of consciousness.

While striking a water balance in our bodies is something that happens naturally as we consume three meals a day coupled with beverages, most people aren't aware that the body is only one or two percentage points away from a problem.

"Very slight changes in body water may create some performance issues in sports; as little as a 2% decrease in body water can lead to dehydration and performance detriments in sports," says Kenney. "When your water levels decrease by higher levels like 3% or 4%, there are physiological changes that occur that may have health consequences, such as increased heart rate and body temperature."

What Counts?

As Debbie Kiley pointed out to the extreme, we need fluids to survive. But what counts? Does the cup of Joe every morning help, or as many believe, hinder? Contrary to the myth, yes, coffee counts when you're tallying fluid intake.

"There is no truth to the idea that coffee makes you dehydrated. That is a pervasive myth," says Kenney, who is a spokesman for the American College of Sports Medicine (ACSM). "The diuretic effect of the caffeine of soda and coffee is mild compared to the amount of fluid they contain."

So coffee and soda count in our quest to stay hydrated. What else can we add to the list?

"You don't have to drink water per se to get water, you can eat watery foods and that will count," says Nancy Clark, a registered dietitian and sports nutritionist in Boston. "Soup counts, yogurt and watermelon count. An orange is 90% water, salads are a lot of water; so all in all, people get plenty of water through foods and beverages other than water."

How Much?

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?

There is a lot of information out there now about hyponatremia (low sodium levels), which is much rarer than dehydration problems, but it can still be a concern, says Kenney.

According to the ACSM web site, "While hyponatremia is a rare occurrence, it is a dangerous condition that may arise when athletes drink too much water, diluting the body's sodium levels. It is most often seen in prolonged endurance athletes, such as those participating in marathons and triathlons."

To strike a balance between too much and too little fluid intake, Kenney recommends weighing yourself before and after exercise, and drinking enough to replace the amount of weight you lose. If you're gaining weight, you know you're drinking too many fluids, and if you're losing weight, you know you need to drink more.

Water Takes the Cake

So we know we need fluids, we know the eight 8-ounce rule isn't backed by science, and we know that we need to strike a balance between too much and too little intake. We also know that almost any fluid will add value to our bodies, but water takes the blue ribbon.

"The body needs water for millions of metabolic processes, temperature control, fluid volume, and lubrication," says Hall. "But many health-conscious folks drink water often because it is a calorie-free thirst quencher. Some research shows that drinking water often may help to suppress the appetite and it certainly aids in digestion."

Water, or any fluid that we drink, is something most of us take for granted. For Debbie Kiley, that's not so.

"There aren't many things I would sell my soul to the devil for, but when I was out on that raft, fresh water was one of them," says Kiley. "I do not take water for granted, that's for sure. It's one of those things in life that seems so available, but when it's not there it's a real bummer."

To say the least.

WebMD Feature


Published December 2005.

SOURCES: Nancy Clark, MS, RD, sports nutritionist; author, Nancy Clark's Sports Nutrition Guidebook, Boston. Rick Hall, MS, RD, advisory board member, Arizona Governor's Council on Health, Physical Fitness, and Sports; faculty member, Arizona Sate University, Phoenix. Larry Kenney, PhD, spokesman; and past president, American College of Sports Medicine, professor of physiology and kinesiology at Penn State, University Park, Pa. Debbie Scaling Kiley, Texas. ACSM web site. WebMD's A to Z Health Guide.

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