Coconut water is often promoted as a healthy way to stay hydrated and a natural alternative to sports drinks. Coconut water contains electrolytes such as potassium, magnesium and sodium, as well as sugar, but is it really better than other rehydration drinks, or even plain water? Do coconut waters on the market contain what they claim, and, if so, which one is best? 

To find out, ConsumerLab purchased and tested popular coconut waters sold in the U.S. The tests revealed wide variations in the amounts of electrolytes in a one-cup serving of each product: ranging from 284.7 to 490 mg of potassium, 20 to 112 mg of sodium, and 6.9 to 66.7 mg of magnesium. Amounts of sugar in a one-cup serving ranged from 6.7 to 11 grams, and one product was found to contain less sugar than listed. None of the products were found to be contaminated with arsenic, cadmium, or lead. The cost per one-cup serving ranged from 72 cents to $1.98 

Among products that were approved, ConsumerLab selected one coconut water as its Top Pick based on quality, nutrition, taste, and cost. 

The results are available online in ConsumerLab's new Coconut Waters Review, which includes test results and comparisons for the following six products selected for testing by CL: Big Tree Farms Coco Hydro Instant Coconut Water, Naked Pure Coconut Water, Taste Nirvana Premium Coconut Water, Trader Joe's Coconut Water, Vita Coco Coconut Water – Organic, and Zico Natural Pure Premium Coconut Water. 

The review also summarizes the clinical evidence for or against coconut water for rehydration, muscle cramps, restless legs syndrome, and kidney stones, and how coconut water compares to sports drinks and water for hydration. It also explains why people with certain conditions and those taking certain medications should limit their intake of coconut water, as well as the potential side effects of drinking too much coconut water, and how coconut water should be stored.