The headline reads: "Coconut Water Is an Excellent Sports Drink" (Science Daily, August 20, 2012; presented at the 244th National Meeting & Exposition of the American Chemical Society (ACS) in Philadelphia). The author states: "Coconut water is a natural drink that has everything your average sports drink has and more. It has five times more potassium than Gatorade or Powerade. Whenever you get cramps in your muscles, potassium will help you to get rid of the cramps. It's a healthy drink that replenishes the nutrients that your body has lost during a moderate workout."
This flies in the face of everything I have learned
• POTASSIUM DEFICIENCY IS NOT A PROBLEM IN HEALTHY EXERCISERS.
In 1967, Dave Costill of Ball State University tried to create
potassium deficiency in runners. He couldn't do it because
potassium is found in all foods except refined sugar, and his
athletes would not stay on a diet that consisted only of hard
candy. The kidneys and sweat glands conserve potassium so well
that you don't lose much. If an athlete develops potassium
deficiency, it is usually caused by drugs, such as diuretics or
corticosteroids, or by diarrhea or repeated vomiting. Some
athletes try to control their weight by making themselves vomit.
This is called bulemia, and the person usually denies vomiting.
Their physicians can prove that they are vomiting by ordering
blood and urine tests. If blood levels of potassium are low and
urine levels are high, vomiting is the likely cause.
• POTASSIUM DEFICIENCY IS NOT A USUAL CAUSE OF CRAMPS OR TIREDNESS
IN EXERCISERS. Tiredness and cramps in athletes can have many
causes, but lack of potassium in the diet is not one of them.
Athletes who are tired and suffer frequent muscle cramps need an
evaluation for other causes of chronic tiredness. If none can be
found, the athlete may be overtraining and should talk to the coach
or a personal trainer about changing workouts.
• THE ONLY MINERAL THAT EXERCISERS NEED TO REPLACE IS SODIUM, COMMON
TABLE SALT. The definitive studies on minerals and exercise were
done during World War II. Dr. James Gamble of Harvard Medical School
paid medical students to lie on rafts in his swimming pool, taking
various amounts of fluids and salt and having blood drawn to measure
salt and mineral levels. He showed that you have to take a lot of
salt when you exercise for several hours, particularly in hot weather.
For many years after that, students at Harvard Medical School heard
Dr. Gamble give his lectures on minerals and exercise, and today,
most serious students still read the Gamble lectures published in
1958 by The Harvard University Press. Now, more than sixty years
later, nobody has improved on his research.
After Gamble published his studies, people who worked or
exercised in hot weather were given salt tablets. Then doctors became
concerned because they thought that a person could have his blood
pressure raised by taking in too much salt, so they recommended
restricting salt, causing many people to suffer heat stroke and
dehydration during hot weather exercise. A low-salt diet does not
lower high blood pressure for most people. A high-salt diet causes
high blood pressure usually only in people with high blood insulin
levels. Eating salty foods and drinks when you exercise for more
than two hours is unlikely to raise blood pressure. We don't
recommend salt tablets because they can cause nausea and vomiting,
but you can use table salt or any salty food.
If you don't take salt and fluids during extended
exercise in hot weather, you will tire earlier and increase your
risk for heat stroke, dehydration and cramps. We eat heavily-
salted potato chips or peanuts and drink fluids at least every
15 minutes when we ride in hot weather. Potassium deficiency doesn't
occur in healthy athletes. The only mineral that athletes need to
take when they exercise is salt.
If you like the taste of coconut water, it is a perfectly
satisfactory fluid to take during exercise, but don't believe claims
that it has any special benefits as a sports drink. If you use it
during intense exercise, you will need other sources of sugar and salt.