Runner's low

Electrolyte supplements do little to keep sodium levels in balance in endurance events, a Stanford Medicine study published Feb. 25 in the Clinical Journal of Sport Medicine showed.

“Electrolyte supplements are promoted as preventing nausea and cramping caused by low salt levels, but this is a false paradigm,” said the study’s lead author, Grant Lipman, MD, professor of emergency medicine.

Illustration by David Plunkert

Sodium maintains blood pressure and regulates muscle and nerve function, so it’s dangerous for levels to be off balance. Hypernatremia occurs when sodium levels are too high, causing dehydration.

Exercise-associated hyponatremia, or EAH, occurs when sodium levels drop, causing altered mental status, seizures, pulmonary edema or even death.

To study the usefulness of supplements, Lipman and his collaborators recruited 266 ultramarathoners who ran 155 miles over seven days, across rough desert terrain.

They collected data on a 50-mile day, weighing runners before their race, asking which electrolyte supplements they planned to use and whether they would drink at intervals or when they felt thirsty.

Afterward, runners reported how closely they followed their plans, were weighed, and gave a blood sample. Forty-one athletes had sodium imbalances: 11 had EAH, and 30 were dehydrated. Each took supplements, but the type, amount and manner of ingestion showed little to no effect on sodium levels.

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