I’m a runner, and have been actively running for over a decade. Since I started running, I’ve consumed Gatorade Lemon-Lime almost exclusively as my as my rehydration fluid of choice. Whenever my run will last over about an hour, I carry and consume Gatorade to offset fluid loss and give me some carbohydrate. The formulation is basic: sugar, salt, and potassium. There are a hundreds of electrolyte products out there, and even Gatorade makes versions with exotic ingredients now. But I’ve been faithful to the original: It’s cheap, I don’t mind the taste (even when its warm), you can buy it nearly anywhere, and it’s a common beverage (besides water) offered at races. Plus, I’ve never been that convinced that it matters all that much – I focus on the engine, not the fuel. After exercise I usually stick with water, preferring to get my electrolytes and carbohydrates from food, rather than liquid sources. But now I’m seeing advertising me that sports drinks are both artificial and inferior. Is it time to upgrade my fuel?
Coconut water isn’t just at the West Indian roti shop anymore: From the grocery store to the yoga studio to the running club, it’s everywhere. The excellent Planet Money podcast recently did a feature on the skyrocketing sales of coconut water, so I decided to take a closer look. Is coconut water a fad beverage, like Vitamin Water was last week, and pomegranate juice the week before? It’s positioned as a superior product for rehydration. The marketing and packaging rely heavily on the naturalistic fallacy, and it’s clearly an appeal to nature: Coconut water naturally contains sugars and electrolytes. Natural is believed to be better than unnatural, therefore coconut water is a better beverage choice. Or is it?
What’s in coconut water?
Don’t confuse coconut water with coconut milk, which contains a lot of coconut “meat”, the white solid we might refer to simply as coconut. Coconut water is the 2-4 cups of fluid inside a young coconut, which declines as the “meat” grows. Depending on when the water is withdrawn, the electrolyte levels may vary, but have been reported in the following ranges [PDF]:
- sodium 0.7-0.9 mEq/L
- potassium 35-82 mEq/L
- glucose 1.2-2.8 grams/L
- calcium 5-17 mEq/L
- magnesium 5-25 mEq/L
There are also small amounts of amino acids, vitamins and minerals present. Compared to a beverage like Gatorade, there’s more potassium, and less sodium and sugar. And unlike Gatorade, coconut has even been directly injected into veins.
The science of treating dehydration has been well evaluated – particularly in the treatment of diarrhea. In most cases, mild diarrhea is a bother. Severe, sustained diarrhea, however, particularly in children, can become life threatening without treatment. Diarrhea kills millions in the third world each year, mainly children under the age of 5. The treatment is simple, but not always available. The World Health Organization’s Oral Rehydration Solution (ORS), which is 6 level teaspoons of sugar and 1/2 level teaspoon of salt dissolved in 1 litre of water, is the considered optimal ratio of sugar and salt to support rehydration. Why sugar and salt in the water? It’s because plain water is not absorbed as well as a solution of salt and sugar. The journal The Lancet called this discovery “potentially the most important medical advance of this century.” The concentration of sugar and sodium will impact on how effectively a beverage will hydrate. How effectively are do the concentrations in a coconut support rehydration? Poorly. Coconut water appears to be inferior for hydration caused by diarrhea. Its electrolyte levels are inadequate – there’s not enough sodium.
So is this information relevant to exercise-induced dehydration? Here there have been some preliminary studies as well. I found three relevant to the question.
- Coconut water was compared to a carbohydrate/electrolye beverage, and plain water, in subjects who exercised in the heat. After exercise subjects drank 120% of their fluid loss. There was no significant difference in the amount of hydration achieved, electrolyte levels, or fluid balance.
- Another study compared plain water, sports drink, coconut water, and sodium-enriched coconut water. Again, subjects exercised in the heat and then rehydrated with 120% of their fluid losses. Here, sports drink and both coconut waters rehydrated to a similar extent and all were slightly superior to water. The sodium-enriched coconut water was reported as better tolerated than other beverages.
- Finally, in an article just published, Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men, coconut water was compared with sports drink and plain water, following exercise-induced dehydration. Yet again, no differences were noted between groups.
So what’s best?
There’s no convincing evidence to suggest that coconut water is a measurably superior beverage for hydration. Coconut water has no magical properties which make it more effective or superior than water or sports drinks when rehydrating. Having said that, many love the taste of coconut water. As a low calorie option, it may be preferred by some over sports drinks with more carbohydrate. Or you can stick with zero-calorie water, and eat something to replenish your electrolytes. Coconut water, or any other beverage, it doesn’t seem to matter for hydration.