Coconut water is all the rage these days. For the record, real coconut water is the clear juice stored inside young, green coconuts. It has long been a popular drink in the tropics. I understand that the U.S. market has grown from near zero five years ago to $50 million today, which suggests that some very clever marketing has been at work. In addition to being promoted as a sports drink, coconut water has been touted as a hangover recovery, an immune system booster and natural protection against cancer. I've seen no convincing research supporting any of these claims.
The defensible selling points for coconut water are that it is cholesterol-free, low in calories, and rich in potassium, providing 569 mg in a typical serving, almost twice the amount in a banana. Ads say that you lose potassium when you exercise strenuously and must replace it. In fact, you lose more sodium than potassium while sweating your way through a vigorous workout, and you can replace both of those minerals by eating some fruits or vegetables after your workout. I don't believe that there's a proven need for any kind of sports drinks after working out, but I do recommend drinking lots of water when you exercise strenuously - more than you think you need.
I don't see any great advantage to coconut water other than the fact that it is natural (although I've read that sugar is added to some brands) and doesn't have the additives found in some sports drinks. However, it is expensive - $2 to $3 for 11 ounces. And it is also an acquired taste. Obviously, coconut water wouldn't be selling as well as it is if some people didn't love it, although some individuals may be drinking it solely because they think it is good for them. Some describe the taste as metallic. When I'm in the tropics, I enjoy drinking the water from whole coconuts. To me, the packaged stuff sold here does not taste nearly as fresh or delicious.
Andrew Weil, M.D.