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H2Overload With experts watering down water's effectiveness, it may be time to rethink the rush for eight glasses a day 
The conventional wisdom that guzzling water provides healthy benefits may no longer be afloat. Sources from folk tales to Web sites credit drinking excess water with a variety of benefits, such as improving skin tone and decreasing toxins in the body. But Dr. Dan Negoianu and Dr. Stanley Goldfarb, University of Pennsylvania, Philadelphia, reviewed scientific papers for evidence of these health effects - only to come up dry. "There's just no evidence for any of these things," says Goldfarb, whose findings were published in the Journal of the American Society of Nephrology. "They just don't make biological sense." These findings are the latest scientific effort to test the urban myths of drinking excess water. Myth #1: Drinking excessive water can rid the body of toxins "There's no reason to expect that that would be the case," Goldfarb says. "Your kidney does excrete toxins, but it doesn't excrete more toxins if you drink more water. It excretes the same amount of toxins in a bigger amount of urine." Myth #2: Drinking lots of water will curb hunger and lead to weight loss While Goldfarb says a small amount of evidence indicates that people who drink water before meals consume fewer calories per meal, "no one has shown that drinking excessive water is going to lead to weight loss. We said that ought to be studied. Probably what happens when people drink a lot of fluids before a meal is you do feel full, and maybe you eat less. But that doesn't mean you are going to lose weight. You may just snack in between meals." Myth #3: Drinking lots of water will combat a headache "One very small study said that there was no benefit," Goldfarb says. "Headaches may occur when you get very dehydrated, but if you're perfectly hydrated, there's no reason to think drinking water would take away a headache." Myth #4: Drinking lots of water will improve skin tone "If you have 60 quarts of water in a 200 pound person, [and] then add a glass of water, it distributes itself throughout your body," Goldfarb says. "It doesn't necessarily go to your skin. And there's especially no evidence it goes to your face. As a matter of fact, because of gravity it doesn't go to your face. Unless you're standing on your head." Myth #5: You need to drink at least eight 8-ounce glasses of water per day "It is a marketing phenomenon that has led to so much water being consumed," Goldfarb says. "There's no absolute number that people need." Currently, the average man takes in three quarts, and the average woman takes in 2.5 quarts of water per day. Forty percent of this comes from the food we eat. Plus, Goldfarb says, "Our bodies generate about a glass of water per day." We take in the rest through juice, soft drinks, coffee and tea. "Our point is that whatever you take in to quench your thirst, you don't need to take in anything above that," he says. "The body is designed not to take in more than what it needs." So how do we know if we are drinking enough water? "The biggest recommendation that can be made about how much water we need each day is to drink when you feel thirsty, and stop drinking when the thirst goes away," says Pamela K. Carmines, professor of cellular and integrative physiology at the University of Nebraska College of Medicine in Omaha. This recommendation is appropriate for normal, healthy adults who live in a temperate climate and who are relatively sedentary - couch potatoes and those whose only exercise is walking. Obviously, if you live in a desert or if you are exercising, Carmines says, you need to drink more to replace water lost through sweat - your thirst will remind you. Can drinking too much water too quickly be harmful? "Definitely, drinking far too much water in a very short amount of time can lead to water intoxication, which can be fatal," Carmines says. "A good example of this situation is the unfortunate death of a contestant in a 'Hold Your Wee for a Wii' contest held by a radio station in California a couple of years ago." How much is too much? "I cannot give even a ballpark figure about how much is too much because it depends on the environment, your activity level and how fast you drink the water," Carmines says. It also depends on your kidney function. "If your kidney function is normal, you can get rid of all of the water that you drink within a reasonable period of time," Carmines explains. "However, if you drink faster than your kidneys can remove the water from your body, water will accumulate and begin to dilute your body fluids. Most individuals will not show any warning signs if the water accumulation develops over several days or weeks, which gives your body time to adapt. However, as your body fluids become more and more diluted, some nondescript symptoms may develop, including malaise, confusion, nausea and fatigue. If you drink too much water within a two-day period, the water accumulation is evident as a weight gain (water weight), and the brain will begin to swell, which can cause severe neurological symptoms: seizures, coma and even death." |
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