Do you drink enough water?
Most People Don't--And That May Be Harming Their Health
A well-conditioned NBA rookie. A 34-year- old businesswoman. A 58-year old executive, recently retired. Each complained of the same symptoms: muscle cramps, headaches, and fatigue, especially near the end of the day. In each case, Susan Kleiner, Ph.D., a registered dietitian in Seattle, suspected the same problem: too little water. "They were all somewhat dehydrated--just dehydrated enough to make their days a little miserable." In each case, a simple water prescription cured the problem.
Those cases are hardly unique: In fact, most people consume less than the optimal amount of water--and a significant number of them do experience symptoms. Moreover, a skimpy water intake may cause more than just symptoms. It clearly contributes to constipation and increases the risk of heat exhaustion or heat stroke. It probably helps cause or worsen asthma, dental disease, kidney stones, and urinary- tract infections. It may even increase the risk of colds and cancer.
Insufficient water intake is a particular concern for older people, because aging, certain drugs (notably sedatives and tranquilizers), and certain diseases (such as diabetes and stroke) may all weaken the sense of thirst. In fact, dehydration is one of the top ten reasons why older people are hospitalized.
Young or old, you need to know whether your body requires more water--and whether wetting your whistle more could really help your health.
The body is constantly losing water via the breath, skin, urine, and feces; the more you weigh, the more water you lose. On a cool, inactive day, the average man loses about 12 eight-ounce cups of water, but takes in only about 9 cups (about half of that from the water in fruits, vegetables, and other solid foods). The deficit eventually triggers enough thirst to restore water equilibrium, but the average man still spends most days slightly dehydrated.
The average woman experiences a somewhat smaller deficit: about 9 cups lost on a cool, quiet day, but only about 7 1/2 cups consumed. However, that 1 1/2-cup shortfall matters more for women, since they generally weigh less than men.
The damage from dryness
Severe dehydration--a net water loss of as little as 4 percent of body weight--can make blood volume and blood pressure plummet, potentially causing muscle spasms, dimmed vision, delirium, fainting, or even a heart attack.
Such drastic problems are relatively rare, since thirst typically kicks in when water loss hits about 2 percent of body weight. But some people may start feeling symptoms of mild dehydration--including headache, fatigue, lightheadedness, muscle cramps, and slightly dulled thinking--after just a 1 percent loss. And the average man's daily water deficit does reduce body weight by about that much; some women with a slightly higher-than-average deficit may also feel the effects of their water shortage.
In addition, some evidence suggests that consuming an ample amount of water may provide more-important health benefits-- possibly including protection against a common killer.
Reduced cancer risk.
Consuming plenty of fluids can speed the elimination of feces from the colon and urine from the bladder, thereby helping to prevent and treat constipation and urinary- tract infection. Researchers now suspect that getting enough fluid might cut the risk of cancer, mainly by flushing out or diluting carcinogens in the bladder and colon.
While that notion is still just theoretical, observational studies do lend some support. In the largest one, a ten-year Harvard study of some 50,000 men, published last May in The New England Journal of Medicine, those who consumed the most fluid had roughly half the bladder-cancer risk of those who consumed the least. Two smaller, earlier observational studies linked a low fluid intake with an increased risk of bladder or urinary-tract cancer; another suggested that drinking at least five glasses of water a day might cut the risk of colon cancer. One very small study even linked consumption of water, but not that of other beverages, with a reduced likelihood of breast cancer-- possibly because water may help wash away or dilute carcinogens not only in the bladder and colon but also in individual cells throughout the body.
Less chance of kidney stones.
Stones form when calcium, uric acid, and other substances in the urine become sufficiently concentrated to form crystals. Drinking lots of liquids helps prevent stones, presumably by keeping those concentrations low. People who've already had kidney stones need as much as two extra quarts of water a day, according to some research, to prevent recurrence.
Fewer asthma attacks.
Researchers have long known that people with asthma have more trouble breathing when it's dry outside, presumably because parched airways don't function properly. Researchers from the University of Buffalo recently showed that lung function declines when asthmatic individuals get dehydrated, increasing the chance of asthma symptoms even in humid weather. (Dehydration similarly dries the mucus membranes in the nose and throat, reducing their ability to trap airborne bacteria and viruses. So dehydration just might increase susceptibility to colds and other respiratory infections.)
Better oral health.
Saliva helps neutralize the cavity-causing acids in the mouth, wash away food particles and sugars, and inhibit the growth of micro-organisms that cause gum disease and other oral problems. Even slight dehydration can reduce saliva. Some people try to moisten their mouth by chewing gum or sucking candy or lozenges rather than by drinking more. But unless you're using sugar-free products, such sugary items compound the risk of cavities--and, of course, they still leave you dehydrated.
In theory, drinking more water, especially with meals, may help curb the appetite by making you feel fuller. While there's no supporting evidence, that simple step is certainly worth trying if you want to slim down. In addition, some people tend to eat rather than drink when they're thirsty, for two possible reasons. Many foods make you feel less thirsty, since they contains some water and relieve dryness in the mouth by stimulating salivation. And some people simply confuse thirst with hunger. Deliberately drinking more can rectify the problem.
Water, water, everywhere
In general, the only people who may be harmed by consuming too much fluid are those whose body retains water due to congestive heart failure, hypothyroidism, or long-term use of certain medications, notably nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, ketoprofen, and naproxen. In addition, men with an enlarged prostate should weigh the possible benefits of ample hydration against the likely inconvenience. But while all those people should avoid drinking excessive amounts of water, they should still try to consume the recommended amount. Nor do people who take diuretics need to worry that the recommended intake of water will interfere with their medication.
You can get your water from a combination of beverages and solid foods. But it probably makes sense to get at least five 8- ounce cups from water itself, partly because it's cheap and calorie-free, and partly because some of the cancer evidence suggests greater protection from water than from other drinks. Other good sources include healthful beverages such as 100 percent fruit juice and low-fat milk or soup. Noncaffeinated soft drinks and fruit drinks also count toward your total, but they're loaded with sugar. And caffeinated or alcoholic drinks don't count at all, since caffeine and alcohol are diuretics--they boost urine output and could leave you more dehydrated than before.
Fruits and vegetables are the best food sources of fluid: Each serving of produce typically provides about one-third of a cup of water. A serving of red meat, poultry, or fish usually provides about one- fourth of a cup; a serving of grain provides about one- sixth of a cup.
Because you may start feeling symptoms of dehydration before you start feeling thirsty, particularly if you're older, don't rely on thirst to guide your water intake. Instead, drink steadily over the course of the day. You can tell you're getting enough fluid if your urine is clear or very pale blue and virtually odorless; dark-blue, strong- smelling urine means you need to drink more.
Most people, particularly men, don't consume enough water. The evidence that the resulting deficit may keep you from feeling your best or may help promote or worsen various health problems--including constipation, urinary-tract infection, kidney stones, asthma, dental disease, and possibly even colds and cancer--is not conclusive. But boosting your fluid intake is so cheap and simple that even a slight possibility of payoffs make that step a good idea for most people.
Try to consume at least 9 to 12 cups of fluid a day, depending on how much you weigh. Drink extra water when you exercise, when it's hot or dry inside or outside, if you're pregnant or breast-feeding, when you consume alcohol or caffeine, or have diarrhea or fever. Aim to get at least half your quota from water itself, the rest from healthful beverages or solid foods, especially fruits and vegetables.
Don't like the taste of plain water? Try sweetening it with saccharin and flavoring it with a small amount of fruit juice.
Another point of view:
No Need to Guzzle All That Water, Expert Says
Fri Aug 9, 7:40 PM ET
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Trying to do the "right" thing by drinking eight full glasses of water a day may do little more than make a person run to the bathroom, a researcher said on Friday.
Newspaper articles, health and beauty magazines all advise drinking at least 8 full glasses of water a day totaling 64 ounces for optimal health -- an approach called "8x8" by proponents.
But Dr. Heinz Valtin of Dartmouth Medical School in New Hampshire said there is no scientific evidence to back up this advice, which has helped create a huge market for bottled water.
"After 10 months of careful searching I have found no scientific evidence that supports '8x8'," Valtin, who has written textbooks on the subject of human water balance, said in a telephone interview.
Writing in the American Journal of Physiology, Valtin, a kidney specialist, said people forget that the food they eat also contains some water.
The Food and Nutrition Board of the National Research Council ( news - web sites) has recommended that people take in about one milliliter of water for each calorie of food eaten.
This adds up to two liters, or 74 fluid ounces on an average 2,000-calorie diet. But the National Research Council also noted that much of this is already contained in food.
"I did 43 years of research on that system -- the osmoregulatory system. That system is so precise and so fast that I find it impossible to believe that evolution left us with a chronic water deficit," Valtin said.
LOW ON FLUID
If a person gets low on fluid, the body compensates by bringing fluid back out of the kidneys and by slowing the loss of water through the skin, Valtin said. Thirst kicks in long before dehydration starts, he added.
"It does it very quickly and very accurately and it does so in minutes," Valtin said.
He said he and colleagues became concerned after seeing dozens of newspaper and magazine articles urging people to sip water all day. "I started talking to my colleagues and asking them 'Do you know of any evidence for this?'. Invariably, they said, 'No I think it's a myth'," Valtin said.
The journal asked him to review all the scientific studies he could find and he concluded that someone misinformed has been telling people to drink large amounts of water when most do not need to.
"I am referring to healthy adults in a temperate climate leading a largely sedentary existence," Valtin said. "Persons with certain diseases must have large volumes of water -- kidney stones are probably the most common example."
The rest can just drink enough to slake thirst -- and this includes coffee, tea, and even beer -- despite their diuretic effects, Valtin said.
He hopes people will be relieved of the guilt of not getting enough water, and of the expense of buying bottled water to drink throughout the day.
"There is also the possibility that if you drink a lot of water that happens to be polluted then of course you get more pollutants," Valtin said.
"Then there is the inconvenience of constant urination, the embarrassment of having to go to the bathroom all the time," he added.
And overdoses of water can cause water intoxication that can lead to confusion and even death. Water intoxication is one deadly effect of taking the drug Ecstasy, for instance, because it makes people thirsty beyond their physical needs.