8 Glasses of Water: Too Much, Too Little and From Where?


water - 8 Glasses of Water: Too Much, Too Little and From Where?


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Sales of bottled water fell in 2009, continuing a four-year decline that appears to be driven by both the recession and a growing sense that it is not the environmentally sustainable choice in beverages.
But there is another benefit to this trend: We’re less obsessed with meeting the mythical requirement of eight glasses of water per day. Traced back to a nutrition book in the 1970s, this myth was encouraged by the bottled water industry, which sought to capitalize on the notion that humans should ingest 64 ounces of water every 24 hours to achieve proper metabolic functions, supple skin and a lower appetite. It turns out there is no such optimal number and no scientific evidence that such benefits result. Also, we generally get a lot of water through foods (particularly fruits and vegetables) and beverages (including milk, soda, tea and coffee).
But even if you drink water from a tap, what possible harm can come from drinking eight glasses? Probably little — if you don’t mind frequent trips to the bathroom — but there are instances of hyponatremia, overhydration that leads to a water-salt imbalance. This sometimes happens to marathon runners and triathletes. A study of 488 runners in the 2005 Boston Marathon found that 13 percent had “dangerously low blood salt levels,” which in all likelihood was due to taking in more water than needed.
(The only relationship between water and hair loss is when you wash your hair in water contaminated with selenium, mercury, zinc, aluminum, arsenic and thallium. The presence of these may be due to local environmental accidents or, sometimes, old lead pipes.)

Sometimes you need more salt

The water-salt balance is no small issue. While most of the developed world contends with too much salt in the diet, athletes and partiers seem to tip the balance too far in the other direction. Deaths due to water intoxication (its other name) have happened in the Houston and Boston marathons, to young adults dancing while on ecstasy and in a water-drinking contest sponsored by a Sacramento, Calif., radio station in 2007.
This is why sports drinks (Gatorade, Powerade and other brands) are touted for their inclusion of electrolytes, which contain sodium, potassium, calcium, chloride and magnesium. These are essential for many bodily functions (the muscle, heart and nerves) and to enable mental focus. The balance can be thrown off by a bad diet, but activities that lead us to sweat (athletics and dancing) expend those electrolytes as well.
Distance athletes — those who know what they’re doing — take salt tablets to achieve that balance. Writing for Inside Triathlon magazine, professional triathlete and sports nutritionist Pip Taylor cautions that overhydrating during a race can flush electrolytes from the body. Additionally, such factors as weather, altitude, pace, relative fitness and other nutrients being consumed before and during contests such as an Ironman triathlon can increase or decrease this imbalance.
In other words, getting that water-salt balance is complicated. Note also that sports drinks should be consumed only when exercising strenuously for more than an hour, says Douglas Casa, Ph.D, director of Athletic Training Education at the University of Connecticut. Casa shared other advice on hydration for sports competitors with National Public Radio reporter Roseanne Pereira:

  • Watch the sugar: Sports drinks are lower in sugar content than fruit juices and sodas; too much sugar is harder to digest, when what you really want is immediate water uptake.
  • Coffee is OK: Caffeine doesn’t hurt and in some ways is beneficial, contrary to the myth that it causes net dehydration.
  • Monitor yourself: If you lose more than 2 percent of your body weight in a training session, you’re not getting enough water. Another indicator of dehydration is when your urine is a dark color (a lemonade hue is preferred).

Bottled water vs. tap water

It’s pretty rare for anyone to overdrink water. Your natural sense of “enough is enough” usually kicks in well before you overhydrate. But how we get hydrated took a funny turn the past several years.
The deadly 1993 outbreak of cryptosporidium in the Milwaukee municipal water supply fueled a nationwide fear of tap water, spurring bottled water sales for a solid decade. Add to that how some tap water just tastes bad — often owing to natural and harmless sulphur content. The Natural Resources Defense Council (NRDC), one of several organizations campaigning against bottled water, found that 47 percent of Americans perceive there to be health and safety problems with tap water that are avoided in bottled water.
More recently, environmentalists have effectively turned bottled water into a drink of shame, with some justification: The 8.7 billion gallons of bottled water sold in the United States in 2007 meant 17 million gallons of oil were used to create the bottles that held this water, according to Food & Water Watch, a nonprofit organization. Only about 14 percent of those bottles would end up being recycled. Another environmental group, the Pacific Institute, says that water extraction, bottle manufacturing, the bottling process and the distribution of bottled water requires 2,000 times more energy than what it takes to get you an equivalent amount of water from a faucet.
Aside from environmental concerns, consumers understandably want to know their water, from whichever source, is clean. To the contrary, the NRDC cites the following:

  • Only 30 to 40 percent of bottled water sold across state lines is regulated by the Food and Drug Administration (FDA); all municipal water sources are vigorously tested for contaminants.
  • Of 103 bottled water brands tested by the NRDC, 25 percent contained bacteria or chemicals that violated state standards.
  • In 2006 the FDA recalled several brands of bottled water with bromate levels that exceeded acceptable levels; bromate is a suspected carcinogen in humans.

Almost all environmental and health organizations endorse the use of water filters in the home if concerns about taste are an issue.
And if even those details are unconvincing, consider the relative costs: Unfiltered tap water costs about $0.002 per gallon. Bottled water per gallon, on average, sets you back $10.66.