Exercise-induced Hyponatremia Caused by Misconceptions Regarding Athletes' Fluid, Sodium Intake

“The prevailing thought used to be that you need to stave off dehydration by drinking before you are really thirsty, but studies have shown this is incorrect. One of the more famous ones was in the New England Journal of Medicine, which showed that a third of participants in the Boston Marathon had low levels of sodium. The US Track and Field Association revised their guidelines advising runners to drink when they are thirsty as opposed to drinking a cup of water every 30 minutes,” Christopher Blewett, MD, said in an interview with HCPLive.

Blewett, a specialist in Pulmonary and Critical Care with Southwest Pulmonary Associates in Plano, TX, advises athletes to start preparing a couple of days in advance of an endurance event by drinking enough water so their urine is a light yellow color and to ease up on NSAID products that can cause water retention.

He says that low sodium levels tend to occur in average athletes after four hours of activity. Disorders of sodium are due to an intake of too much water or excretion of too much water. Endurance athletes tend to drink too much water and they don’t replace their sodium loss when they sweat.

“The key is to not drink so much water and to replace salt loss with sodium or salt tablets like NUNN. One misconception is that sport drinks contain electrolytes, sodium, and potassium. They certainly contain more than water, but drinking sports drinks alone isn’t going to automatically guarantee what you won’t get hyponatremia. Once a race or event is finished, the tendency is to drink a lot of fluids rapidly, but you have to be careful of what you drink. Athletes need to eat a banana, Clif bars, gels or candies or drink a glass of milk…. some kind of recovery food that isn’t just pure water,” Blewett said.

He also said that athletes should weigh themselves after a race or endurance activity to check for weight loss because weight gain is a sign of hyponatremia. He said that hyponatremia is hard to diagnose because the symptoms of confusion, fatigue, disorientation, and nausea mimic the signs of dehydration.