What's Up With all the Coconut Water?

By Trisha Brooke Stavinoha | March 06, 2019, 5:35 p.m. (ET)

Heavenly Water

Coconut water has become quite popular lately. It’s listed as a recommended rehydration source by various organizations to treat exertional heat illness and dehydration (1-3). Some athletes and sports teams are recommending or endorsing versions of it. So here’s what you need to know.

You will see coconut water described as being high in electrolytes—but fresh coconut water is only high in potassium and is quite low in sodium. Sodium and chloride are the primary electrolytes lost in sweat. Potassium is lost as well, but at much lower levels. When sweating, we lose 3-4 mg of sodium for every 1 mg of potassium. At a minimum, a sports drink should contain 460 mg sodium per liter. Most coconut waters on the market have less than 300 mg sodium per liter and up to 1,800 mg potassium. Athletes who are quoted as using coconut water for sweat replacement use a “sodium-enriched” version, but don’t necessarily state how much sodium is in the product.

The nutrition profile for coconut waters is diverse. The term “natural” seen on many labels has no real definition, and 38% of commercial coconut waters have added sugars (5). This explains the range of calories and sugar in various products. Some products use Erythritol, a sugar alcohol used to lower calories. Erythritol is considered safe to use, but side effects include nausea, gas and may have a laxative effect, causing diarrhea (6). That makes this type of beverage highly inappropriate to use during sport or to treat dehydration.

A study indicating coconut water was as effective as a sport drink used a sodium-enriched coconut water with 460 mg sodium per liter (7). Individuals in the study were 3% dehydrated. This means a 150-pound individual lost just over 2 liters fluid. The problem with the study is that being as effective as a sport drink when this dehydrated meant neither was that effective at fully rehydrating. There was not enough sodium with this level of dehydration and subjects urinated out some of the fluids before they could absorb them. Individuals who are this dehydrated need a beverage with at least 800 mg sodium per liter. “Endurance” formula sports drinks contain about 800 mg sodium per liter and are better suited for extreme heat and subsequent high sweat conditions that result in significant dehydration.

Other studies that quote fresh coconut water being as effective as water or a sport drink are hydrating individuals who were not that dehydrated. This level of dehydration is actually pretty common after an hour workout and would not put someone at a state of heat emergency.

A study comparing coconut water to plain water consumed during exercise showed if people did not like the taste of the beverage, they won’t drink it (9). Fluids with sodium that taste good promote greater consumption than plain water or a beverage they don’t like. This should not be surprising!

What if someone is severely dehydrated to the point they need medical attention? The World Health Organization recommends 800 mg potassium per liter in an oral rehydration solution (ORS) with at least 1,380 mg sodium, with sodium being the more critical electrolyte to replace (11). Coconut water is the exact opposite of this, which will delay rehydration.

One particular medical condition that corresponds with severe dehydration is rhabdomylosis. “Rhabdo” is characterized by muscle pain, muscle weakness and dark urine. Potassium levels increase to the point of putting the individual at risk for cardiac arrest and kidney damage (12). This is a case where the level of potassium in coconut water would be extremely harmful.

Bottom line: If you like the taste, coconut water is fine for an everyday drink or for hydration maintenance, but not for sweat replacement. If you are dehydrated or doing an activity for over an hour that makes you sweat, consider a product with more sodium. Use the table below to help determine when coconut water might be appropriate for hydration. 

Not dehydrated: Thirsty, chilling on the beach, need a beverage to maintain hydration levels

Water is best, but coconut water, soda, tea, or anything but alcohol will do the job.

Needing fluid, Starting to sweat: Exercising, working outside, working up a sweat, but not significant yet. Goal to prevent dehydration.

Water, coconut water, or traditional sport drink if less than an hour. The longer the individual is sweating, the more they need something with sodium to keep them hydrated.

Dehydrated 2-3%:

Have been exercising or working outside for a while, perhaps not drinking during or out longer than expected, sweating a lot

“Endurance” sport drink with 200 mg sodium per 8 oz. If this is not available, eat something salty with water like potato chips or pretzels with water. You will need to add salt if you use coconut water or traditional sport drinks. ¼ teaspoon salt has 590 mg sodium.

Dehydrated >3% medical condition: Athlete cutting weight, diarrhea, heavy sweating without concurrent hydration

An Oral Rehydration Solution. If not available, see recommendation above. Traditional sport drinks, coconut water, soda or plain water could be harmful due to the high sugar and inadequate sodium.

References

  1. Red Cross First Aid Guidelines
  2. Kaplan E. Hockey players’ love affair with coconut water.
  3. Zelman KM. The Truth About Coconut Water.
  4. Kalman DS, Feldman S, Krieger DR, Bloomer RJ. Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men. Journal of the International Society of Sports Nutrition. 2012, 9:1.
  5. Psomiadis D, Zisi N, Koger C, Horvath B, Bodiselitsch B. Sugar-specific carbon isotope ratio analysis of coconut waters for authentication purposes. Journal of Food Science Technnology. 2018. 55(8):2994-3000.
  6. Sweet Nothings, Safe or scary? The inside scoop on sugar substitutes. NutritionAction.com® Center for Science in the Public Interest.
  7. Ismail I, Singh R, Sirisinghe RG. Rehydration with sodium-enriched coconut water after exercise-induced dehydration. Southeast Asian Journal of Tropical Medicine and Public Health 2017, 38:4
  8. Saat M, Singh R, Sirisinghe RG, Nawawi M. Rehydration after exercise with fresh young coconut water, carbohydrate-electrolyte beverage and plain water. Journal of Physiological Anthropology and Applied Human Science. 2002, 21:2.
  9. Peart DJ, Hensby A, Shaw MP. Coconut water does not improve markers of hydration during sub-maximal exercise and performance in a subsequent time trial compared with water alone. International Journal of Sport Nutrition and Exercise Metabolism. 2017; 27:179-184.
  10. Baker LB, Jeukendrup AE. Optimal composition of fluid-replacement beverages. Comprehensive Physiology. 2014, 4.
  11. Gregorio GV, Gonzales MLM, Dans LF, Martinez EG. Polymer-based oral rehydration solution for treating acute watery diarrhea. Cochrane Library. Cochrane Database of Systematic Reviews. 2016.
  12. Rhabdomyolysis Symptoms, Causes, and Treatments

 


Trisha Brooke Stavinoha, MS, RD, CSSD, CSCS, TSAC-F, MAJ, USA Army (retired), retired from 20 years as an Army dietitian and now consults for Cera Products, Inc. She was a member of the All Army sports program and still competes in triathlon, running, trail running and obstacle course events. For questions, she can be reached at trishastavinoha@yahoo.com, or at tstavinoha@ceraproducts.us.