Question of the Week

April 8, 2008


There have been recent reports that question the need to drink eight 8-ounce glasses of water throughout the day. For years people have been told that this is important, but no one seems to know why.

"Scientists say there's no clear health benefit to chugging or even sipping water all day. So where does the standard advice of drinking eight glasses each day come from? 'Nobody really knows,' says Dr. Stanley Goldfarb, a kidney expert at the University of Pennsylvania."

This doesn't mean that people should stop drinking water.

"All living things must have water to survive, whether they get it from a water fountain, a rain cloud, or a little bottle attached to the side of a hamster cage. Without water, your body would stop working properly. Water makes up more than half of your body weight and a person can't survive for more than a few days without it. Why? Your body has lots of important jobs and it needs water to do many of them. For instance, your blood, which contains a lot of water, carries oxygen to all the cells of your body. Without oxygen, those tiny cells would die and your body would stop working. Water is also in lymph (say: limf), a fluid that is part of your immune system, which helps you fight off illness. You need water to digest your food and get rid of waste, too. Water is needed for digestive juices, urine (pee), and poop. And you can bet that water is the main ingredient in perspiration, also called sweat. In addition to being an important part of the fluids in your body, each cell depends on water to function normally."

It makes sense: the bigger the person, the more water they need for their body to function properly. On the other hand, if a person is smaller, they can lose less water before they begin to suffer from dehydration.

"Dehydration sets in when a person has lost 2 percent of his or her body weight. So for a 200-pound man, this means losing 4 pounds of water. Marathon runners, bikers and hikers all need to recognize the signs of dehydration. 'It is also obvious that individuals in hot, dry climates have increased need for water,' says Goldfarb."

Whatever the size of the person, the amount of water consumed needs to make up for the amount of water used by the body. Otherwise, dehydration becomes a problem.

"Dehydration occurs when you lose more fluid than you take in and your body doesn't have enough water and other fluids to carry out its normal functions. If lost fluid remains unreplenished, you may suffer serious consequences. ... Mild dehydration can cause symptoms such as weakness, dizziness and fatigue. Severe dehydration is a life-threatening medical emergency. You can usually reverse mild to moderate dehydration by increasing your intake of fluids, but severe cases need immediate medical treatment. The safest approach is not to become dehydrated in the first place. You can do that by monitoring your fluid loss during hot weather, illness or exercise, and drinking enough liquids to replace what you lose."

Drinking enough to replace what you lose is important, but water is not the only drink. Water is often the recommended drink of choice because it contains no calories. When people get their liquids from soda, or even juice, these drinks can contain excess calories and simple sugars.

"When selecting a juice, buyer beware: many so-called juices contain little real juice and have more added sugar than anything else. So read the label carefully. Your best choice is one that is 100% fruit or vegetable juice -- not a 'juice drink,' 'fruit flavored drink' or a sugar-heavy 'blend.' And even when it is 100% juice, remember that juices lack the fiber of whole fruit. ... Don't get me wrong -- pure fruit juice is nutritious as well as delicious, containing a whole host of vitamins, minerals, antioxidants, and phytochemicals. It's much better than drinking a soda. But even pure fruit juices are high in naturally occurring simple sugars. So unless you eat them along with other foods, they can send your blood sugar soaring... And those natural sugars can add up to lots of calories. A glass of fruit juice ranges from 100 (orange, grapefruit, apple) to 170 (grape and prune) calories for an 8-ounce serving."

Water is not the only drink, and drinking is not the only way that people get the fluids they need.

"Your body doesn't get water only from drinking water. Any fluid you drink will contain water, but water and milk are the best choices. Lots of foods contain water, too. Fruit contains quite a bit of water, which you could probably tell if you've ever bitten into a peach or plum and felt the juices dripping down your chin! Vegetables, too, contain a lot of water. Think of slicing into a fat tomato from the garden or crunching into a crisp stalk of celery."

Getting enough fluids is important, but, as with anything, too much of a good thing can be bad.

"Hyponatremia is an abnormally low concentration of sodium in your blood. When your blood sodium is too low, your cells malfunction -- causing swelling. In chronic hyponatremia, sodium levels drop gradually over several days or weeks -- and symptoms are typically moderate. In acute hyponatremia, sodium levels drop rapidly -- resulting in potentially dangerous effects, such as rapid brain swelling, which can result in coma and death. Hyponatremia occurs when the sodium in your blood is diluted by excess water. Hyponatremia may result from medical conditions that impair excretion of water from your body, or by a significant increase in water consumption, such as by athletes competing in marathons and other high-endurance events."

Questions of the Week:
How does the amount of fluids that you need to consume to keep your body healthy vary from day to day? What might make it higher on one day and less on another? How does the amount of liquids you need to consume vary from the quantity needed by another person? From what sources can you get the fluids that you need? In what ways are some sources better than others? How can you tell when you are getting enough to drink and when you are not?

Please email me with any ideas or suggestions.
Note: Due to increasing amounts of SPAM sent to this account, please include "QOW" in the subject line when sending me email.

I look forward to reading what you have to say.

Health Community Coordinator
Access Excellence @ the National Health Museum

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