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Marathon Hydration: Water Overload Danger
29 Oct
Summary
- Excessive fluid intake during exercise can cause low blood sodium.
- Hyponatremia symptoms include nausea, headache, and confusion.
- Drink to thirst, not by a set amount, to stay safely hydrated.
Marathon runners face a health risk from overhydration, specifically exercise-associated hyponatremia (EAH). This condition occurs when excessive fluid intake dilutes sodium levels in the blood, a critical electrolyte. Even sports drinks can contribute if consumed in excess, as the body's hormone arginine vasopressin signals the kidneys to retain water during exercise.
A 2005 study in The New England Journal of Medicine highlighted this risk, finding EAH in 13% of Boston Marathon runners. Symptoms such as nausea, headache, dizziness, and fatigue can mimic dehydration. Severe cases may lead to confusion, seizures, or loss of consciousness, requiring immediate medical attention.
To avoid EAH, experts recommend drinking according to thirst rather than consuming large volumes at every checkpoint. While no specific volume is universally dangerous, listening to your body is key. Medical professionals can distinguish EAH from dehydration through a patient's fluid intake history and blood sodium tests, ensuring appropriate treatment. This article is for informational purposes only and not a substitute for professional medical advice.
