Does coconut water hydrate better than water?

• Default serving330 mlWater
• Counts toward goal347 mlhydration factor 1.05
• Calories63 kcal19 kcal per 100 ml

Sodium holds fluid; potassium is not a substitute

Coconut water is genuinely rich in potassium: roughly 250 mg per 100 ml, more than the same volume of most sports drinks carry. It is also low in sodium, usually somewhere near 25 mg per 100 ml. That combination is the mirror image of what a rehydration drink is designed around.

Fluid retention is largely a sodium story. Drink a large volume of something with little salt in it and plasma sodium drops. That switches off the hormone that tells the kidneys to hold water. The surplus leaves within the hour. In the Beverage Hydration Index trial, the drinks that measurably beat plain water were oral rehydration solution and milk. One is loaded with sodium and glucose. The other carries sodium, lactose, protein and fat. Fruit juices and sports drinks sat close to water, and coconut water belongs in that group.

What the 1.05 factor represents

The app gives coconut water a hydration factor of 1.05 and counts a 330 ml serving as 347 ml. The small bonus reflects the sugar and mixed electrolytes, which slow the passage through your stomach a little. It is not a claim of a superior fluid. Five percent is a rounding error next to drinking a second glass.

Where it earns its place is after heavy sweating, and even there with a caveat. Sweat is rich in sodium and poor in potassium. That is precisely the balance coconut water fails to replace. Pair it with something salty and the pairing works. On its own it is a pleasant, mildly sweet way to hit your goal.

The calories are real

63 calories in a 330 ml carton, from about 4 to 5 g of natural sugar per 100 ml. That is a third of a cola, but it is not the zero of tap water. Cartons labelled "with juice" or "with pulp" go higher. A litre a day of it in hot weather is nearly 200 calories you would not get from water. That is why the app puts a calorie figure on every drink you log, sugary or not.

Hydration factors follow the Beverage Hydration Index: Maughan RJ, Watson P, Cordery PA, et al. “A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.” American Journal of Clinical Nutrition, 2016;103(3):717-723. Read the paper on PubMed. In WaterChamp a coconut water counts for slightly more than plain water.