Coconut water has taken over the shelves of grocery stores in the past few years, and nutritionists say that some of the hype may in fact be deserved.

The drink comes from young, green coconuts, and is rich in potassium and antioxidants. And, compared with sodas or even sports drinks, coconut water is relatively low in calories and sugar. However, the product should not replace water as the main source of hydration, according to experts.

"Coconut water is another beverage option on the market that does offer some nutritional benefits," Allison Massey, a registered dietician at Mercy Medical Center in Baltimore, told Live Science in an email. For instance, it is a source of potassium and small amounts of sodium, magnesium, calcium and phosphorus, she said.

However, experts stress that regular water should still be the main source of hydration, and it is best to incorporate coconut water as an additional beverage option from time to time.

"Generally, water should be a staple when it comes to hydration," Massey said. "Coconut water is simply another beverage option that can be incorporated in moderation as part of a well-balanced diet, if individuals enjoy drinking it." [10 New Ways to Eat Well]

Excellent potassium source

Previous research has shown that a 12-ounce serving of coconut water has more potassium than a banana. Coconut water also has much more potassium than sport drinks like Gatorade or Powerade. An 11.2-ounce serving of coconut water has 690 mg of potassium, whereas a 12-ounce serving of Gatorade has 140 mg of the nutrient.

Potassium helps eliminate muscle cramps that may sometimes follow workouts, Chhandashri Bhattacharya, a lecturer in chemistry at Indiana University Southeast in New Albany who has analyzed coconut water, said in a statement.

As a means of hydration, drinking coconut water can be a good option for some people, depending on the kind of workout they do, experts say.

"It depends on the individual, and intensity, as well as duration of activity," Massey said. "Generally, if individuals are exercising less than 60 minutes, water is the best choice for hydration."

And if a workout involves in strenuous exercise that produces a lot of sweat, a sports drink might be a better alternative than coconut water because it will more effectively replenish electrolytes, Bhattacharya said. That's because coconut water may not be sufficient to replenish sodium, as it only has 400 mg/liter of sodium, whereas sports drinks may contain 600 mg/liter of the mineral.

However, the typical American diet is already high in sodium (coming mainly from salt), and low in potassium.

Is it fattening?

Coconut water, when unsweetened, contains around 40 calories per 8.5-ounce serving, Massey said.

"Having 40 calories in a drink is not unreasonable," said Kristin Kirkpatrick, a registered dietician at the Cleveland Clinic. Coconut water has almost no fat, and it is "five times better [for you] than" regular sodas, which contain more calories and sugar, she said.

However, both Kirkpatrick and Massey noted that coconut water is a source of calories, and it takes about 3,500 extra calories to gain a pound.

Drinking coconut water "is not absolutely necessary," for health, Kirkpatrick said. However, its electrolytes may be beneficial, for instance, on a hot day when you are sweating a lot.

What is in coconut water?

While these days it is a good idea to be cautious about whether a product actually contains the fruit or substance it is supposed to contain, the majority of products sold as coconut water actually seem to include the claimed ingredient. "Most coconut waters that I have seen on the market come from an open coconut," Kirkpatrick said.

However, consumers should still check the labels, as some types of coconut water do include added sugars or juices, Massey said.

Interestingly, because the fruit's tough shell protects coconut water, the substance is relatively sanitary, and anecdotal evidence suggests it can be used as human blood plasma in emergencies, according to a study published in 2000 in the American Journal of Emergency Medicine. Coconut water and blood plasma have similar compositions.

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