For years our mothers and doctors told us we should drink lots of water each day. How much is enough? Americans say 8 glasses, and some say probably between 8 to 10 glasses.
It's a rule that is familiar to almost everyone. But it seems to have no basis in fact. Researchers at the University of Pennsylvania searched for the origin of the eight-glasses-a-day theory by going back through at least three decades of scientific data. They found nothing conclusive.
Dr. Stanley Goldfarb of the University of Pennsylvania Medical School is the senior author of this latest study says it is easy to understand how the idea of drinking large quantities of water got started-water is needed to sustainlife, then obviously that's led people to think: Well, if a normal amount is good, then extra might be better.
Dr. Goldfarb and his colleagues looked at five claims about drinking water -- the first, that large amounts help flush out toxins from the kidneys. They say no study provided evidence to support that.
Another claim is that the body's organs work efficiently with more water. The Pennsylvania scientists say the body's retention of water depends on the speed it is taken in. Sipping helps the body maintain greater amounts of water, they say, than gulping it.
Dieters have often been told the more water they drink, the less hungry they will feel. Again, there are two conflicting studies about the merits of water for weight reduction.
Two other claims -- that lots of water improves skin tone and helps prevent headaches -- were also unproven.
So, how much is enough? The scientists say 11 glasses of any kind of liquid is good for women and 15 is recommended for men. But that includes other fluids we drink or even the food we eat.
Dr. Goldfarb says we should just listen to what our bodies tell us. "Drink when you're thirsty. That's the way the body is designed."
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