How much is too much when it comes to hydrating? The human body needs fluids to compete in extreme races like marathons, but there’s a point when drinking more water can be dangerous.
According to Running USA, 541,000 US runners completed marathons in 2014 — predominantly in the warmer months. Running 26.2 miles in the heat seems like it would warrant almost endless amounts of water, so what makes overhydrating a problem for some athletes?
Hyponatremia is a problem relatively common to runners. It occurs when there is too little sodium (salt) in the blood — often due to too much fluid intake. The body’s response to too little sodium is to move water into the cells in an attempt to restore the balance — which can cause the cells to swell.
This can result in fatigue and confusion. In extreme cases, hyponatremia can be deadly.
Marathon runner David Rogers, for example, passed away in 2007 after running the London Marathon. It was a warm day, and the athletes were advised to hydrate frequently. The 22-year-old was one of 70 people to be rushed to the hospital that day, reports The Times. He died after a severe case of hyponatremia.
Marathoner Kate Mori also developed hyponatremia at the 2007 London Marathon. She started feeling sick around the 18th mile.
"I didn't think I'd overhydrated at all, because I was just having little sips," Mori told The Wall Street Journal.
A doctor later told Mori that she’d had about three-quarters of a gallon of water during the race and advised her to drink much, much less than that next time, according to The Wall Street Journal.
According to the Wall Street Journal, a study of runners at the London Marathon found that about 13 percent experienced hyponatremia.
Tim Noakes, a sports medicine physician at the University of Cape Town in South Africa, told The Wall Street Journal that athletes should drink according to how thirsty they feel to stay healthy and maximize their performance.