Water, water everywhere, but how much should we drink?
It is a debate that seems to never be put to rest in part because doctors and health organizations send conflicting messages.
Many physicians will offer up the eight-glass-a-day adage, though there is no actual research suggesting why this amount should be a goal. For our skin, for our waistline, for our kidneys -- little snippets of advice seem to be perpetually passed around, all consolidating in a singular chant: drink more water, it's good for you.
But why? This is the question that a group of dissenting medical opinions have been posing over the past few years. In a nutshell, their argument is this: there's no evidence that drinking more water helps our health, so shouldn't we just drink when we're thirsty?
That's the take-home message Dr. Margaret McCartney, a Scottish physician, is putting forth in her opinion piece published in the British Medical Journal Tuesday.
The concept that we must drink six to eight glasses of fluids a day to prevent dehydration is "not only nonsense, but is thoroughly debunked nonsense," she writes.
McCartney is up in arms about the western world's tendency to over promote water in large part because she feels that promotion is guided by the beverage industry, not by medical science.
"We can emphasize non-evidenced based things too much," she told ABCnews.com, which detracts from the real health messages we should be sending about exercise diet, and not smoking.
McCartney also calls out several water myths that are currently promoted by European bottled water producer, Danone: that drinking water will help you lose weight, that kids need to drink more water in order to concentrate in school, and that the lack of those eight glasses a day will lead to health problems.
"There is still no evidence that we need to drink more than we naturally want," she writes.
Water Myths Busted
McCartney isn't the first water myth buster. Back in 2008, Dr. Stanley Goldfarb, a nephrologist at the University of Pennsylvania Perelman School of Medicine, and colleagues tackled several common water health myths that were circulating around the Internet at that time.
"We found that there really is no evidence that drinking more water makes you perform better. It doesn't reduce appetite, it doesn't lead to long-term weight loss, and it can't possibly improve your complexion. It won't clear your body of toxins or reduce headaches," Goldfarb told ABCnews.com.
"There's just no basis for these contentions," he said.
Goldfarb's article, released at a time when bottled water consumption was at an all-time high and American's aquaphilic fervor at its peak, garnered a lot of attention.
Goldfarb said he would find himself in tiffs even with the reporters who interviewed him, many of whom didn't want to accept that drinking lots of water didn't seem to provide any health benefits.
Goldfarb attributes some of the persistence of the water myths to the fact that many physicians will back the urge to drink plenty of water because "it really can't hurt you" and it's a "free, easy health message to give." After all, what's the harm in drinking more water than you need?
And the answer, both McCartney and Goldfarb agree is, not much. Drink too much water (as long as it's not an extremely large amount of water) and you'll just pee it out.
The Water Intake That's Right for You
Where the harm comes in, McCartney argues, is when the call to "drink more water" becomes the marketing call to "drink more bottled water." As a nation, Americans consume more than 8 billion gallons of bottled water annually, up from about 5 billion in 2001, according to the International Bottled Water Association.
"The notion that you have to drink water from Fiji is insane. That's part of America -- people are taken in by marketing issues," said Goldfarb.
And "what about all the plastic bottles, the transport of water round the country, and subsequent environmental harm?" McCartney said.
The bottom line is simple: dehydration is bad, but if you're in good health and drinking when you're thirsty, you probably fine.
"Thirst is a highly developed sensation, powerfully motivated. When you're thirsty, all you want to do is drink. But being thirsty doesn't mean you are ill at this point or dehydrated to the point that there are consequences," Goldfarb said.
Another measure? Watch the color of your urine, said Dr. Randy Wexler, a physician and assistant professor at Ohio State University. "The more clear the urine, the better the hydration. The darker..the more dehydrated."
If you exercise or are out on a hot day and sweating, you'll need more water for sure, but then again, your body will tell you that with thirst, Goldfarb added.