Summary
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What is coconut water?
Coconut water is the clear to slightly cloudy liquid found in immature (green) coconuts. It is rich in potassium, contains a moderate amount of sugar, and modest amounts of sodium, magnesium, calcium, vitamin C, and phosphorus. Unlike coconut milk and coconut oil, it contains very little fat — less than 1 gram per cup. See What It Is. -
How is coconut water used?
Drinking coconut water is a pleasant way to hydrate and re-hydrate but has generally not been shown to be better than water in this regard. Although preliminary research suggested a possible role for coconut water in preventing kidney stone formation, this has not been proven in people. See How It's Used. -
What did CL's tests of coconut water find?
Among six popular coconut water products tested by ConsumerLab, five were found to contain what they claimed with regard to sugar and key minerals and none was contaminated with arsenic, cadmium, or lead. One product was found to contain significantly less sugar than claimed. Based on a one cup serving, the products contained 6.7 to 11 grams of sugar, 284.7 to 490 mg of potassium, 20 to 112 mg of sodium, and 6.9 to 66.7 mg of magnesium -- although the higher amounts of sodium and magnesium were in a product in which these were added ingredients. The cost per cup ranged from 72 cents to $1.98. See What CL Found. 
Best coconut water?
ConsumerLab selected a Top Pick among coconut waters based on quality, nutrient levels, taste, and cost.-
How to store coconut water?
Coconut water does not have to be refrigerated until the container is opened. See ConsumerTips. -
Safety and side effects of coconut water:
Due to the large amount of potassium in coconut water, intake should be limited among people with severe kidney disease or on medications that affect potassium levels. Even healthy people should only consume coconut water in moderation, and be aware that natural coconut water will not adequately replace sodium after long, strenuous exercise (for electrolyte replacement see our Electrolytes & Sports Drinks Review), and it can have a laxative effect. For details, see Concerns and Cautions.
