Saturday, April 5, 2008

Water's benefits questioned by scientists

Water_3Why are they so irritated by water?

Six years ago, scientists trashed the "eight glasses of water a day" dictum, in part because no one could figure out where it came from.

Now there's no reason to feel guilty for not hydrating during aerobics class because there's not much evidence showing that drinking "lots" of water will improve our health, according to the editorial "Just Add Water" by University of Pennsylvania researchers in the Journal of the American Society of Nephrology.

That means excessively hydrating won't necessarily clear toxins from your system, keep organs healthy, curb hunger pains, reduce headaches and improve your skin tone, said authors Dan Negoianu and Stanley Goldfarb of Penn's Renal, Electrolyte and Hypertension Division.

"Our purpose was to relieve people of the burden that they have to drink extra water in order to be healthy," co-author Stanley Goldfarb told me. "There's no evidence of that."

But while the researchers say they wish they could "demolish all the urban myths found on the Internet regarding the benefits of supplemental water ingestion,"they never tell us what "excess" water consumption is. How much is too much?

And what they ultimately concede after reviewing the literature is that there's not enough evidence for either side: No clear data exists for a lack of benefit, either.

In the review, Goldfarb and Negoianu looked at what they consider to be "four major myths" of extra water drinking: that it helps excrete toxins, improves skin tone, reduces appetite and helps cure headaches. Here's a brief look at what they found.

  • Excrete toxins: The human body is made up of 60 percent water, so a 200-pound person consists of 120 pounds of water or 15 gallons, said Goldfarb. He contends that adding a cup of water to 15 gallons wouldn't make much of an impact.

"In fact, drinking a lot of water very quickly tends to lower blood flow to the kidney," Goldfarb said. "That actually impairs its ability to excrete toxins," he said.

But they also found that several studies reveal that drinking water does have an impact on clearing various substances by the kidney, including sodium and urea. These studies, however, do not indicate any sort of clinical benefit that might result.

  • Skin tone: Goldfarb maintains that whenever you ingest water, it's distributed equally throughout the body; there's no reason the skin would get preferential treatment. Plus we have so much skin that the possibility that a few ounces would have an effect seems unlikely and there's no evidence that this has been carefully studied.
  • Reduces appetite: Studies are inconclusive but there is a possibility that if you drink water before you eat, it would stay in the stomach--a small volume area--and suppress your appetite. But drinking water with meals didn't seem to have the same effect, and no one has looked at the possibility whether it leads to weight loss, Goldfarb said.

On the other hand, studies have shown that drinking diet soft drinks can lead to obesity. So drinking water instead of diet soda might confer health benefits.

  • Headaches: Dehydration can make you feel ill and give you non-specific headaches, but that's different from stress and tension headaches, Goldfarb said. Only one small trial (15 migraine sufferers) has addressed the question, and the researchers found participants who increased their water intake experienced fewer headaches than those who did not. To me, that sure sounded like evidence of a health benefit. But the results were "not statistically significant" according to the study.

When I asked Doctor Alexa Fleckenstein, co-author of "Health20--Tapping into the Health Power of Water" what she thought of the editorial, she agreed that water is not a cure-all.

"And I definitely abhor seeing people everywhere running around with a glass or a bottle in their hands - you never need water that urgently, at least not if you are not hiking," she told me. "Even in aerobics class drinking can wait until you are done."

But Fleckenstein, who wrote Health20 with Roanne Weisman, is a firm believer in water's healing properties and tells people to drink seven glass per day.

"Not because I have a study but precisely because there is NO study giving the exact amount - and seven is a sacred number," she said.

Moreover, we all require different amounts of water because of "different climates, different sizes, different exertion, different clothing (to name a few of the parameters)," she said.

(The average intake is about a quart a day, and most experts say to drink when you're thirsty.)

Fleckenstein says that "common sense and observations in daily life show that skin turgor is better when one drinks enough: I can always tell when my husband forgot to drink - he looks 10 years older."

She adds anecdotally:

"I found out that my ear problems during flights are much improved if I keep solidly hydrated. Other than that, the authors are right: We have no studies. Wish we had!"

Original here

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