A graduate of the George Washington University Medical School Board, Dr. Sainsbury is certified in emergency medicine. He was a full-time emergency physician for 25 years, has lived on the Central Coast since 1990, and has written for many magazines. He currently has a house call practice here on the Central Coast and visits Africa yearly to help patients and student doctors there. Visit Dr. Sainsbury.com
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Water Myths
by Steve Sainsbury, MD
Our bodies are 65-70% water—obviously a crucial component to good health. Is it any wonder that myths abound surrounding its use? Here are just a few.
MYTH: You need to drink at least 8 glasses of water a day to stay hydrated.
A certain subset of Americans love to exercise. Go to the gym and you will hear the trainer's frequent refrain, "Drink up, people. Stay hydrated." Cyclists, joggers, and hikers are everywhere—look closely and many are constantly drinking water. Even non-exercisers are told to drink water regularly, whether they are thirsty or not.
Much of this emphasis on water intake stems from the myth that we need to drink at least eight glasses of water a day. This misconception probably arose from a Nutrition and Food Board study that estimated that the typical active adult needs 64-80 ounces of fluid daily. Ignored is that the same report stated that 20% of this intake would commonly come from any foods that are ingested.
There is no harm in drinking eight glasses of water daily, but neither is there an absolute necessity to do so. Thirst is a reliable indicator or our water needs. Regardless of our individual needs, I suspect that many water-guzzling exercisers are getting far more water than they really require. Especially those that are barely even working up a sweat.
MYTH: If you wait to feel thirsty to drink, it's too late.
Thirst has evolved over the course of time to enable us to stay hydrated. It is a highly developed, protective mechanism. How much sense would it make if we only got thirsty after it was too late to avoid dehydration? (Answer: It wouldn't make any sense at all.) In reality, thirst is a reliable indicator of our hydration status and can be trusted.
MYTH: Caffeinated drinks will only make your dehydration worse.
This myth undoubtedly originates from the fact that caffeine is indeed a mild diuretic that stimulates urination. Cola drinks, for example, contain small to moderate amounts of caffeine (about half the caffeine in coffee). However, the amount of fluid contained in a 12 oz Pepsi or Coca Cola easily compensates for the mild diuretic effect. If it is a hot summer day, and Mountain Dew is your only available drink—go for it. The beneficial effects of the fluid in the soda far outweigh the negligible diuretic effect.
Incidentally, many people assume that sports drinks containing electrolytes will always restore electrolyte losses from sweating. This may not always be true. Very active athletes can sweat up to two liters per hour. Aggressively hydrating with sports drinks will not keep up with electrolyte losses—salty snacks may be necessary to maintain salt balance.
MYTH: Bottled water is healthier than tap water.
This is one of the biggest scams around. Bottled water costs about 2,000 times the price of tap water, and in many blinded studies tastes no different. It is not healthier, and contains no special nutrients. Amazingly, some bottlers get their water from the same sources as tap water suppliers. Unless taste is really a factor, save your money—fill your water bottles with good, old-fashioned tap water. Only your wallet will know the difference.
MYTH: Water purifiers and filters make your water safer.
Municipal tap water is safe—free of bacteria, heavy metals, and dangerous impurities. Purifiers are not needed to make safe water safer. The only legitimate use of filters or purifiers would be to improve the taste.
Mountain Gorilla image on banner by Steve Sainsbury.
This particular one is Steve's favorite gorilla, a friend from one of his stays in Rwanda.
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