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Prevent Hyponatremia During Exercise Lasting Four Hours Or Longer

Dangerous drop in blood sodium levels can lead to seizures, coma, death

Hyponatremia occurs where sodium levels in the blood become dangerously low due to excessive water consumption.  Blood sodium levels that drop too low can lead to seizures, coma, and even death. To prevent hyponatremia during endurance and ultra-endurance events lasting longer than 4 hours (such triathlons, ultra-marathons, long distance cycling, or, for slow marathon runners, a regular marathon), your child should observe the following guidelines:

  • Avoid water loading before the event.   There is no need for your child to try to superhydrate before the event; his body can absorb only such fluid, and if he overdrinks, he then may need to (inconveniently) urinate during the race;

  • Eat salted foods and fluids (soup, pretzels, salted oatmeal) 90 minutes before exercise;

  • Drink an endurance sports drink with higher sodium amounts than the standard sports drink;

  • Consume salty foods during the endurance event, as tolerated (vegetable juice, broth, pickles, cheese sticks);

  • Stop drinking water during exercise if the stomach is "sloshing," as may happen if the athlete drinks more than a quart (32 oz. or 1 liter) of water per hour for extended periods.

Nancy Clark, MS RD CSSD,is MomsTeam's sports nutrition expert, a Certified Specialist in Sports Dietetics and best-selling author.  She counsels active people in her practice at Healthworks, a fitness center in Chestnut Hill, Massachusetts. Her new book, Food Guide for Soccer:Tips & Recipes from the Pros and other books, including her Sports Nutrition Guidebook (from which this article is adapted) and food guides for new runners, marathoners, and cyclists are available at www.nancyclarkrd.com and www.sportsnutritionworkshop.com.